Method and application of flocculant concentration detection and molecular weight determination in sand washing wastewater

Abstract

The present disclosure provides a method and use for detecting the concentration of flocculants in sand-washing wastewater and determining the molecular weight, the method comprising: S1, preparing an indicator standard solution, anionic polyacrylamide standard solutions of different concentrations and different molecular weights; S2, establishing a detection circuit; S3, using the indicator standard solution, the anionic polyacrylamide standard solution and the detection circuit to obtain a concentration-slope standard curve; wherein the slope is the slope of the current-filled solution volume curve; S4, pre-treating the sand-washing wastewater to be tested, using the detection circuit to obtain the slope to be tested, and then obtaining multiple concentrations; S5, using multiple concentrations of anionic polyacrylamide standard solutions, the sand-washing wastewater to be tested and the detection circuit to detect the current, using the standard curve to determine the molecular weight of the flocculant, and then obtaining the flocculant concentration. The method disclosed in the present disclosure can quickly determine the concentration and molecular weight of the flocculant in the sand-washing wastewater at the construction site, and judge whether it can be reused based on this, thereby improving the reuse rate of freshwater resources.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a method and application for detecting the concentration of a flocculant in sand washing wastewater and determining its molecular weight. Background Art

[0002] Fresh water is a key resource for maintaining life, supporting economic activities, ensuring social stability and promoting environmental protection. Protecting fresh water resources and rationally utilizing and managing water resources are vital to the current and future human society. However, concrete mixing plants or construction sites consume a lot of water resources when cleaning sand and gravel aggregates, and this part of water resources has not been effectively reused, which is not conducive to the sustainable development of water resources. The water used for concrete preparation and the water used for cleaning sand and gravel aggregates usually come from the same source. The difference between the two and sand washing wastewater is that sand washing wastewater contains impurities attached to sand and gravel aggregates. The present disclosure is dedicated to the water quality testing of sand washing wastewater, in order to use qualified sand washing wastewater for concrete preparation, so as to greatly improve the recycling of water resources in concrete mixing plants and construction sites.

[0003] The purpose of cleaning sand and gravel aggregates at concrete mixing plants or construction sites is to remove mud powder, stone powder and impurities introduced during the production of machine-made sand. Usually, in the production of machine-made sand, anionic polyacrylamide (APAM) is often used as a flocculant to quickly flocculate suspended matter in the sedimentation tank to improve the circulation efficiency of production water and thus improve production efficiency. Therefore, the impurities introduced during the production of machine-made sand are mainly APAM. Therefore, sand washing wastewater contains a large amount of stone powder, mud powder and APAM still attached to machine-made sand and gravel aggregates. These substances will seriously affect the fluidity and strength of concrete.

[0004] Although mud powder and stone powder will affect the fluidity of concrete, they can be removed by filtering. However, APAM attached to machine-made sand and gravel aggregates will fully dissolve in the sand washing wastewater and cannot be directly removed. A large number of experimental studies have shown that when the residual amount of APAM flocculant in the machine-made sand reaches 0.003% of the mass of the sand (based on the mixing water amount, the aqueous solution concentration is 0.018%), the fluidity of the mortar will be significantly reduced; when the residual amount of APAM in the machine-made sand reaches 0.009% of the mass of the sand (based on the mixing water amount, the aqueous solution concentration is 0.054%), the optimal amount of polycarboxylic acid water reducer will be ineffective; when the residual amount of APAM in the machine-made sand further increases, the fluidity of the mortar will further deteriorate, which will seriously affect the pumpability of the concrete. Therefore, the APAM content in sand washing water is the main factor limiting the recycling of sand washing wastewater in the preparation of concrete.

[0005] Therefore, it is necessary to strictly control the content of flocculants in wastewater, that is, to use sand washing wastewater for concrete preparation, greatly improving the water resource reuse efficiency of mixing plants or construction sites. To control the content of flocculants in sand washing wastewater, it is necessary to establish a reasonable detection method. APAM, which is common in the market and commonly used in the production of machine-made sand, can be divided into 18 million molecular weight and 22 million molecular weight according to molecular weight, and the detection is relatively difficult.

[0006] The APAM attached to machine-made sand has not only unknown content but also unknown molecular weight. The molecular structure and performance of APAM with different molecular weights are significantly different, and its influence on the fluidity and strength of concrete is also very complex. Developing a detection method only for a single molecular weight APAM will ignore the influence of other molecular weight APAM on the test results, greatly limiting the efficiency of water resource reuse. In addition, when reusing sand washing wastewater from concrete mixing plants and construction sites, technicians have a greater demand for high detection efficiency and low detection cost. If this can be achieved, it will be able to better evaluate the degree of reuse of sand washing wastewater in the preparation of concrete, which can not only ensure the quality of concrete projects, but also greatly improve the reuse efficiency of freshwater resources.

[0007] Therefore, a low-cost, high-precision, high-efficiency and universal sand washing wastewater quality detection method is needed to quickly determine the water quality of sand washing wastewater at the construction site and provide applicable solutions to improve the reuse rate of freshwater resources. Summary of the invention

[0008] In view of this, the first aspect of the present disclosure provides a method for detecting the concentration of a flocculant in sand washing wastewater and determining the molecular weight, comprising: S1, preparing an indicator standard solution and anionic polyacrylamide standard solutions of different concentrations and different molecular weights; S2, establishing a detection circuit; the detection circuit comprises a first solution pool, a third solution pool, a fourth solution pool, and a second solution pool connected in series in sequence, wherein a power supply is electrically connected to the first solution pool and the second solution pool, respectively, and an ammeter is electrically connected to the first solution pool and the fourth solution pool, respectively; the fifth solution pool to the eighth solution pool are respectively connected to the first solution pool to the fourth solution pool pipeline; S3, using the indicator standard solution, the anionic polyacrylamide standard solution and the detection circuit to obtain a concentration-slope standard curve; wherein the slope is the slope of the current-filled solution volume curve; S4, pre-treating the sand washing wastewater to be tested, using the detection circuit to obtain the slope to be tested, and then obtaining multiple concentrations; S5, using multiple concentrations of anionic polyacrylamide standard solutions, the sand washing wastewater to be tested and the detection circuit to detect the current, using the standard curve to determine the molecular weight of the flocculant, and then obtaining the flocculant concentration.

[0009] According to the embodiments of the present disclosure, the solute of the indicator standard solution in S1 is one or more of copper sulfate, ferric sulfate, ferric chloride, and copper chloride, and the concentration of the indicator standard solution is 1g / L~5g / L; the concentration of the anionic polyacrylamide standard solution in S1 is 0.012%~0.060%, and the molecular weight is 18 million~22 million.

[0010] According to an embodiment of the present disclosure, the fifth solution tank to the eighth solution tank in S2 are respectively connected to the first solution tank to the fourth solution tank through a hose and a peristaltic pump.

[0011] According to an embodiment of the present disclosure, the detection circuit in S2 further includes a single chip microcomputer for analyzing the concentration of the flocculant.

[0012] According to an embodiment of the present disclosure, obtaining a concentration-slope standard curve in S3 includes: S31, adding an indicator standard solution, deionized water, deionized water, and deionized water with a volume of V0 to the first solution pool to the fourth solution pool, respectively, and adding an anionic polyacrylamide standard solution of standard concentration to the fifth solution pool to the eighth solution pool; S32, using a peristaltic pump to uniformly add the standard solutions in the fifth solution pool to the eighth solution pool to the corresponding first solution pool to the fourth solution pool; S33, using an ammeter to detect the current at a certain interval to obtain a concentration-slope standard curve at the standard concentration; S34, repeating steps S31 to S33 to obtain standard curves at different concentrations and different molecular weights.

[0013] According to an embodiment of the present disclosure, the flow rate of the liquid added by the peristaltic pump at a uniform speed in S32 is 50-100 ml / min.

[0014] According to an embodiment of the present disclosure, the pretreatment in S4 includes: filtering the sand washing wastewater to be tested through at least two stainless steel sieves with different pore sizes in sequence, and the pore sizes of the at least two stainless steel sieves with different pore sizes are reduced in sequence.

[0015] According to the embodiments of the present disclosure, obtaining the slope to be measured by using the detection circuit in S4 includes: S41, adding the indicator standard solution, deionized water, deionized water, and deionized water with a volume of V0 to the first solution pool to the fourth solution pool, respectively, and adding the pretreated sand washing wastewater to be measured to the fifth solution pool to the eighth solution pool; S42, using a peristaltic pump to uniformly add the standard solution in the fifth solution pool to the eighth solution pool to the corresponding first solution pool to the fourth solution pool; S43, using an ammeter to detect the current at a certain interval to obtain the slope to be measured, and then obtain multiple concentrations.

[0016] According to an embodiment of the present disclosure, determining the molecular weight of the flocculant using a standard curve in S5, and then obtaining the flocculant concentration includes: S51, adding a first concentration of anionic polyacrylamide standard solution among multiple concentrations to the first solution pool and the third solution pool, adding a second concentration of anionic polyacrylamide standard solution among multiple concentrations to the second solution pool and the fourth solution pool, and obtaining a first current using a detection circuit; wherein the liquid volumes in the four solution pools are the same; S52, adding an equal volume of pretreated sand washing wastewater to be tested to the four solution pools, and obtaining a second current using a detection circuit; S53, if the first current is greater than the second current, the flocculant molecular weight is the molecular weight corresponding to the first concentration of anionic polyacrylamide standard solution; otherwise, it is the molecular weight corresponding to the second concentration of anionic polyacrylamide standard solution; S54, obtaining the flocculant concentration according to the flocculant molecular weight and the corresponding standard curve.

[0017] A second aspect of the present disclosure provides a use of the aforementioned method for detecting flocculant concentration and determining molecular weight in sand washing wastewater, for determining whether the sand washing wastewater to be tested can be used for preparing concrete according to the determined flocculant concentration and molecular weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0019] Figure 1 A flow chart schematically shows a method for detecting flocculant concentration and determining molecular weight in sand washing wastewater according to an embodiment of the present disclosure;

[0020] Figure 2 The structure diagram of the detection circuit according to the embodiment of the present disclosure is schematically shown;

[0021] Figure 3 Schematically showing two standard curves of APAM flocculants with molecular weights of 18 million and 22 million according to the embodiments of the present disclosure;

[0022] Figure 4 Schematically shows the current-filling solution volume curve and slope k according to the embodiment of the present disclosure x Schematic diagram of

[0023] Figure 5 Schematically shows the use of slope k according to an embodiment of the present disclosure x Schematic diagram for calculating flocculant concentration;

[0024] Description of reference numerals:

[0025] 1, first solution pool; 2, second solution pool; 3, third solution pool; 4, fourth solution pool; 5, fifth solution pool; 6, sixth solution pool; 7, seventh solution pool; 8, eighth solution pool; 9, electrode; 10, wire; 11, power supply; 12, ammeter; 13, peristaltic pump; 14, hose. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0027] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0028] In order to solve the current problems of large demand for freshwater resources, low recycling rate and waste of resources in the construction site for washing sand and gravel aggregates, and to avoid direct discharge of wastewater containing pollutants such as sediment and flocculants to pollute the environment, a water quality detection equipment and method based on the reuse of sand washing wastewater to prepare concrete is developed. By detecting the type and concentration of flocculants in the sand washing wastewater, a threshold is used to determine whether the sand washing wastewater can be used to prepare concrete. The sand washing wastewater that meets the threshold requirements is retained for the preparation of concrete, and a treatment plan is given for the sand washing wastewater that exceeds the threshold. The present disclosure aims to improve the recycling rate of freshwater resources at the construction site and reduce resource waste.

[0029] The present disclosure provides a method for detecting the concentration of flocculants in sand washing wastewater and determining the molecular weight. Figure 1 , including: S1, preparing indicator standard solution, anionic polyacrylamide standard solution of different concentrations and different molecular weights; S2, establishing a detection circuit; the detection circuit includes a first solution pool, a third solution pool, a fourth solution pool, and a second solution pool connected in series in sequence, wherein the power supply is electrically connected to the first solution pool and the second solution pool respectively, and the ammeter is electrically connected to the first solution pool and the fourth solution pool respectively; the fifth solution pool to the eighth solution pool are respectively connected to the first solution pool to the fourth solution pool pipeline; S3, using the indicator standard solution, the anionic polyacrylamide standard solution and the detection circuit, a concentration-slope standard curve is obtained; wherein the slope is the slope of the current-filled solution volume curve; S4, pre-treating the sand washing wastewater to be tested, using the detection circuit to obtain the slope to be tested, and then obtaining multiple concentrations; S5, using multiple concentrations of anionic polyacrylamide standard solutions, the sand washing wastewater to be tested and the detection circuit to detect the current, using the standard curve to determine the molecular weight of the flocculant, and then obtaining the flocculant concentration.

[0030] The main purpose of the present disclosure is to provide a water quality detection equipment and method based on the reuse of sand washing wastewater to prepare concrete, in order to quantitatively evaluate the molecular weight and concentration of APAM in sand washing wastewater, and improve the reuse efficiency of sand washing wastewater in concrete mixing plants or construction sites. Since the APAM content in sand washing wastewater is unknown, the molecular weight is also unknown; it is difficult to directly perform molecular weight and content detection on APAM at the construction site. The method disclosed in the present disclosure first obtains a concentration-slope standard curve of APAM of different concentrations and different molecular weights, and then determines the concentration and molecular weight of APAM in sand washing wastewater based on the same detection circuit according to the standard curve.

[0031] Specifically, the present disclosure utilizes the flocculation effect of APAM on harmful ions or special media, and uses the change in solution conductivity to characterize the concentration change of a solution of known concentration, thereby inverting the type of unknown flocculant and the concentration of the flocculant in the solution. This is completely different from the method of testing the viscosity, absorbance, and turbidity of the flocculant aqueous solution in the already disclosed test methods, and is also different from the method of testing the fluidity change of mortar or cement paste, and is an innovative test method. In addition, the detection method involved in the present disclosure is not limited to the need for high-value detection equipment (such as ion chromatograph, spectrophotometer, etc.), nor is it limited to a specific flocculant, but can simultaneously realize APAM concentration testing of different molecular weights.

[0032] On the basis of the above embodiment, the solute of the indicator standard solution in S1 is one or more of copper sulfate, ferric sulfate, ferric chloride, and copper chloride, and the concentration of the indicator standard solution is 1g / L~5g / L; the concentration of the anionic polyacrylamide standard solution in S1 is 0.012%~0.060%, and the molecular weight is 18 million~22 million.

[0033] Copper sulfate, ferric sulfate, etc. are selected as standard solutions because the concentration of the indicator solution is within the above range, which is conducive to the full complexation of anionic polyacrylamide with copper ions or iron ions in the solution at extremely low concentrations, and promotes the phase separation of the complex in the solution and the formation of precipitation. At this time, there is no anionic polyacrylamide remaining in the first solution pool, while there is anionic polyacrylamide in other solution pools. The change in circuit current is only caused by anionic polyacrylamide, so the concentration of anionic polyacrylamide can be inferred based on the change in current.

[0034] On the basis of the above embodiment, the fifth solution tank to the eighth solution tank in S2 are respectively connected to the first solution tank to the fourth solution tank through a hose and a peristaltic pump.

[0035] Figure 2The schematic diagram of the detection circuit in the present disclosure is shown, including: a first solution pool 1, a second solution pool 2, a third solution pool 3, a fourth solution pool 4, a fifth solution pool 5, a sixth solution pool 6, a seventh solution pool 7, an eighth solution pool 8, an electrode 9, a wire 10, a power supply 11, an ammeter 12, a peristaltic pump 13, a hose 14 and a single chip. The first solution pool 1, the second solution pool 2, the third solution pool 3, and the fourth solution pool 4 are connected in series using wires, the positive electrode of the power supply 11 is connected to the positive electrode of the first solution pool 1, and the negative electrode of the power supply 11 is connected to the negative electrode of the second solution pool 2; the positive electrode of the ammeter 12 is connected to the negative electrode of the first solution pool 1, and the negative electrode of the ammeter 12 is connected to the positive electrode of the fourth solution pool 4. The fifth solution pool 5, the sixth solution pool 6, the seventh solution pool 7, and the eighth solution pool 8 are respectively connected to the first solution pool 1, the second solution pool 2, the third solution pool 3, and the fourth solution pool 4 via the hose 14 and the peristaltic pump 13. Among them, the use of a peristaltic pump can effectively ensure that the liquids in the fifth solution pool to the eighth solution pool can be added to the first solution pool to the fourth solution pool at a corresponding uniform speed, which is beneficial to the subsequent drawing of a standard curve.

[0036] On the basis of the above embodiment, the detection circuit in S2 further includes a single chip microcomputer for analyzing the concentration of the flocculant.

[0037] When the standard solutions in the fifth to eighth solution pools are added to the corresponding first to fourth solution pools at a uniform speed, the single chip microcomputer is used to record the current value and the added volume, draw the current-added solution volume curve, and calculate the slope k x The microcontroller has a built-in standard curve for calculating the flocculant concentration Φ. The built-in standard curve of the microcontroller is the slope k of the current-filled solution volume curve drawn for a flocculant of a certain concentration and type. x Value and flocculant concentration Φ x relationship curve.

[0038] On the basis of the above embodiment, the concentration-slope standard curve obtained in S3 includes: S31, adding the indicator standard solution, deionized water, deionized water, and deionized water with a volume of V0 to the first solution pool to the fourth solution pool, respectively, and adding the anionic polyacrylamide standard solution of standard concentration to the fifth solution pool to the eighth solution pool; S32, using a peristaltic pump to uniformly add the standard solutions in the fifth solution pool to the eighth solution pool to the corresponding first solution pool to the fourth solution pool; S33, using an ammeter to detect the current at a certain interval to obtain a concentration-slope standard curve at the standard concentration; S34, repeating steps S31 to S33 to obtain standard curves at different concentrations and different molecular weights.

[0039] Taking 18 million molecular weight and 22 million molecular weight APAM standard solutions with standard concentrations of 0.012%~0.060% and 1g / L copper sulfate standard solution as examples, the drawing of the standard curve of the present disclosure is explained, wherein the concentration step is 0.012%. During the test, one portion of 1g / L copper sulfate standard solution and three portions of deionized water were injected into the first solution pool to the fourth solution pool, respectively, and 4 portions of APAM standard solution of each standard concentration were injected into the fifth solution pool to the eighth solution pool, respectively, and the current indication number I1 was recorded. The standard solutions in the fifth solution pool to the eighth solution pool were added to the first solution pool to the fourth solution pool respectively using a peristaltic pump, and the current value I2 and the added solution volume V were recorded every 5s. b , calculate the slope k of the current-filled solution volume curve at the current concentration x Then, different concentrations Φ x The multiple k obtained under x Value EstablishmentΦ x ~k x The relationship curve is the standard curve.

[0040] Based on the above embodiment, the flow rate of the liquid added by the peristaltic pump at a uniform speed in S32 is 50-100 ml / min.

[0041] The liquid flow rate within the above range is conducive to the full reaction of the flocculant and the standard liquid during the filling process, and at the same time has the shortest reaction time, which can greatly shorten the detection time.

[0042] On the basis of the above embodiment, the pretreatment in S4 includes: filtering the sand washing wastewater to be tested through at least two stainless steel sieves with different pore sizes in sequence, and the pore sizes of the at least two stainless steel sieves with different pore sizes are reduced in sequence.

[0043] Filtering the sand washing wastewater to be tested multiple times is conducive to better removing the machine-made sand solids and avoiding affecting the subsequent detection process. Preferably, the sand washing wastewater to be tested is sequentially passed through 200 mesh, 300 mesh, 500 mesh and 1000 mesh stainless steel sieves to obtain pre-treated samples, and the flocculant content in the sand washing wastewater is quantitatively analyzed using detection equipment and solution conductivity.

[0044] On the basis of the above embodiments, the slope to be measured is obtained by using the detection circuit in S4, including: S41, adding the indicator standard solution, deionized water, deionized water, and deionized water with a volume of V0 to the first solution pool to the fourth solution pool, respectively, and adding the pretreated sand washing wastewater to be measured to the fifth solution pool to the eighth solution pool; S42, using a peristaltic pump to uniformly add the standard solution in the fifth solution pool to the eighth solution pool to the corresponding first solution pool to the fourth solution pool; S43, using an ammeter to detect the current at a certain interval to obtain the slope to be measured, and then obtain multiple concentrations.

[0045] The standard curve is the slope k of the current-injection solution volume curve drawn for the flocculant with a certain concentration and molecular weight. x Value and flocculant concentration Φ x After obtaining the standard curve, the flocculant concentration test can be carried out on the sand washing wastewater to be tested. Take one portion of the standard solution and three portions of deionized water of equal volume and put them into the first solution pool to the fourth solution pool of the detection circuit respectively. The volume of the standard solution and deionized water taken is V0. The output current value I1 is obtained by testing; add equal amounts of pretreated sand washing wastewater to the four solution pools respectively, and test and obtain the output current value I2 at the same time; according to the current change rate, standard curve, and the volume of the pretreated sample V x 、Add standard solution volume V S , calculate the flocculant concentration Φ.

[0046] On the basis of the above embodiment, the standard curve is used to determine the molecular weight of the flocculant in S5, and then the flocculant concentration is obtained, which includes: S51, adding a first concentration of anionic polyacrylamide standard solution among multiple concentrations to the first solution pool and the third solution pool, adding a second concentration of anionic polyacrylamide standard solution among multiple concentrations to the second solution pool and the fourth solution pool, and obtaining a first current by using a detection circuit; wherein the liquid volumes in the four solution pools are the same; S52, adding an equal volume of pretreated sand washing wastewater to be tested to the four solution pools, and obtaining a second current by using a detection circuit; S53, if the first current is greater than the second current, the flocculant molecular weight is the molecular weight corresponding to the first concentration of anionic polyacrylamide standard solution; otherwise, it is the molecular weight corresponding to the second concentration of anionic polyacrylamide standard solution; S54, obtaining the flocculant concentration according to the flocculant molecular weight and the corresponding standard curve.

[0047] Further, concentration Φ is added to the first solution pool and the third solution pool respectively. a Add the standard solution of concentration Φ to the second solution pool and the fourth solution pool. b The volume of the standard solution added is the same, and the current value A3 is recorded. The same volume of pre-treated sand washing wastewater to be tested is added to the first solution pool, the second solution pool, the third solution pool, and the fourth solution pool at the same time, and the current value A4 is recorded. If A3>A4, the molecular weight of the flocculant in the sand washing wastewater to be tested is the concentration Φ a The molecular weight of the standard solution, otherwise the concentration Φ b The corresponding molecular weight.

[0048] The specific reasons for judgment are as follows: If the molecular weight of the flocculant in the sand washing wastewater to be tested is a concentration of Φ a The molecular weight corresponding to the standard solution is Φ, so when the sand washing wastewater to be tested is added to the four solution pools, it is equivalent to diluting the concentration Φ bThe standard solution of Φ results in a decrease in conductivity and an increase in resistivity, which is manifested in a decrease in current value. If the molecular weight of the flocculant in the sand washing wastewater to be tested is a concentration of Φ b The molecular weight corresponding to the standard solution is equivalent to increasing the concentration Φ when the sand washing wastewater to be tested is added to the four solution pools. a The concentration of the standard solution increases, resulting in an increase in conductivity and a decrease in resistivity, which is manifested in an increase in current value. Therefore, the molecular weight and corresponding concentration of the flocculant in the sand washing wastewater can be directly determined based on the change in current value.

[0049] The present disclosure also provides a use of the aforementioned method for detecting flocculant concentration and determining molecular weight in sand washing wastewater, for determining whether the sand washing wastewater to be tested can be used for preparing concrete according to the determined flocculant concentration and molecular weight.

[0050] Determine whether the wastewater quality can be used to prepare concrete based on the flocculant concentration Φ and threshold Φ0:

[0051] For sand washing wastewater with Φ<Φ1, it is filtered through a stainless steel screen and then collected in a bottle for use in preparing concrete.

[0052] For sand washing wastewater with Φ1≤Φ<Φ2, it is purified by ion exchange resin and then used to prepare concrete.

[0053] Sand washing wastewater with a diameter of Φ≥Φ2 cannot be used to prepare concrete and must be retained in the sand washing pool for further cleaning of sand and gravel aggregates, pending retesting.

[0054] Specifically, for example, the flocculant threshold Φ1 for judging whether the wastewater quality can be used to prepare concrete is 0.018%, and the threshold Φ2 is 0.054%. The flocculant threshold corresponding to the flocculant threshold for judging whether the wastewater quality can be used to prepare concrete is k x The values ​​are -0.167 (18 million molecular weight anionic polyacrylamide) and -0.119 (22 million molecular weight anionic polyacrylamide).

[0055] The present disclosure is further described below through specific implementation methods. The rapid detection method and use of the type of residual flocculant in the above-mentioned machine-made sand are specifically described in the following examples. However, the following examples are only used to illustrate the present disclosure, and the scope of the present disclosure is not limited thereto.

[0056] The rapid detection method of the type of residual flocculant in the machine-made sand of this embodiment comprises the following steps:

[0057] Prepare sand washing wastewater samples; filter the samples through stainless steel meshes with different apertures in turn to obtain pretreated sand washing wastewater to be tested; prepare copper sulfate solution of standard concentration as standard solution; take one portion of standard solution and three portions of deionized water of equal volume and put them into the first solution pool to the fourth solution pool of the detection circuit respectively, the volume of the standard solution and deionized water taken are both V0, and the output current value I1 is obtained by testing; add equal amounts of pretreated sand washing wastewater to be tested to the four solution pools respectively, and simultaneously test to obtain the output current value I2; according to the current change rate, standard curve, and the volume V of the pretreated sample added x 、Add standard solution volume V S , calculate the flocculant concentration Φ; determine whether the wastewater quality can be used to prepare concrete based on the flocculant concentration Φ and the threshold Φ0.

[0058] For sand washing wastewater with Φ<Φ1, it is filtered through a stainless steel screen and then collected in a bottle for use in preparing concrete.

[0059] For sand washing wastewater with Φ1≤Φ<Φ2, it is purified by ion exchange resin and then used for preparing concrete. The ion exchange resin is an anion exchange resin.

[0060] Sand washing wastewater with a diameter of Φ≥Φ2 cannot be used to prepare concrete and must be retained in the sand washing pool for further cleaning of sand and gravel aggregates, pending retesting.

[0061] In the above scheme, the solution pool is made of transparent and corrosion-resistant material, the electrodes are graphite electrodes or platinum sheet electrodes, the wires are pure copper wires with shielding mesh, the power supply voltage is adjustable from 0 to 20V, and the ammeter accuracy is 1μA.

[0062] In the above scheme, the slope k x The calculation method is:

[0063]

[0064] In the above scheme, if Figure 3 As shown, there are two standard curves, corresponding to flocculants APAM with molecular weights of 18 million and 22 million respectively.

[0065] In the above scheme, the standard curve is obtained by conductivity method testing. First, prepare 18 million molecular weight and 22 million molecular weight APAM solutions with standard concentrations of 0.012%~0.060%, with a concentration step of 0.012%. During the test, one portion of 1g / L copper sulfate solution and three portions of deionized water are injected into the first solution pool to the fourth solution pool, respectively, and 4 portions of APAM solution of each standard concentration are injected into the fifth solution pool to the eighth solution pool, respectively, and the current indication number I1 is recorded. Use a peristaltic pump to add the standard solutions in the fifth solution pool to the eighth solution pool to the first solution pool to the fourth solution pool, respectively, and record the current value I2 and the added solution volume V every 5s. b , calculate the slope k of the current-filled solution volume curve at the current concentration x Then, different concentrations Φ x The multiple k obtained under x Value EstablishmentΦ x ~k x The relationship curve is the standard curve.

[0066] In the above scheme, if the molecular weight of APAM is determined, the same k x The multiple concentrations corresponding to the values ​​are recorded as Φ a and Φ b , each concentration corresponds to a molecular weight.

[0067] In the above scheme, when determining the molecular weight, first empty the liquids in the first solution pool to the fourth solution pool, and then add the concentration of Φ to the first solution pool and the third solution pool respectively. a Add the standard solution of concentration Φ to the second solution pool and the fourth solution pool. b The standard solution is added in the same volume, and the current value A3 is recorded. The same volume of pre-treated sand washing wastewater to be tested is added to the first solution pool to the fourth solution pool at the same time, and the current value A4 is recorded. If A3>A4, the molecular weight of the flocculant is the concentration Φ a The molecular weight of the standard solution, otherwise the concentration Φ b The corresponding molecular weight.

[0068] In the above scheme, the threshold Φ1 is 0.018%, and the threshold Φ2 is 0.054%.

[0069] According to the above steps, a specific embodiment is provided below.

[0070] Embodiment 1:

[0071] S01: Prepare 1L of sand washing wastewater sample;

[0072] S02: The sand washing wastewater samples were passed through 200 mesh, 300 mesh, 500 mesh and 1000 mesh stainless steel sieves in turn to obtain pretreated sand washing wastewater. 400 ml of the pretreated sample was taken and divided into 8 equal parts, 50 ml each;

[0073] S03: Prepare 400 ml of 2 g / L copper sulfate solution as standard solution and divide it into 2 portions, 200 ml each;

[0074] S031: Take 1 portion of the standard solution and add it to the first solution pool of the detection circuit. Take 3 portions of deionized water, 200 ml each, and add them to the second solution pool, the third solution pool, and the fourth solution pool of the detection circuit respectively. Take 4 portions of pretreated sand washing wastewater and add them to the fifth solution pool to the eighth solution pool of the detection circuit respectively.

[0075] S032: Connect the wires, turn on the power supply, adjust the output voltage to 5V, and after the ammeter reading stabilizes, the microcontroller starts recording the output current value I1.

[0076] S033: Connect the peristaltic pump and the hose, and start to add the pre-treated sand washing wastewater to the first solution pool, the second solution pool, the third solution pool, and the fourth solution pool. The flow rate is set to 5ml / min, and the single-chip computer records the current value I2 every 5s. The single-chip computer internally calculates the slope k of the current-filled pre-treated sample volume curve x .

[0077] S04: k x Substitute the value into the standard curve and compare to obtain the flocculant concentration Φ in the pretreated sample x , which is the flocculant concentration Φ in the sand washing wastewater.

[0078] S041: When judging different molecular weights of APAM, k x The values ​​will correspond to two concentrations, denoted as Φ a and Φ b , each concentration corresponds to a molecular weight.

[0079] S042: Prepare concentration of Φ a and Φ b APAM standard solution of corresponding molecular weight, 2 portions of each, 4 portions in total, 50 ml each.

[0080] S043: Do not remove the wire, only empty the solution pool, and then add concentration Φ to the first solution pool and the third solution pool respectively. a Add the standard solution of concentration Φ to the second solution pool and the fourth solution pool. bThe same volume of standard solution is added to the first solution pool, the second solution pool, the third solution pool, and the fourth solution pool. The same volume of pre-treated sand washing wastewater is added to the first solution pool, the second solution pool, the third solution pool, and the fourth solution pool. The current value A4 is recorded. If A3>A4, the molecular weight of the flocculant is the concentration Φ a The molecular weight of the standard solution, otherwise the concentration Φ b The corresponding molecular weight.

[0081] S05: Compare the concentration Φ with the threshold values ​​Φ1: 0.018% and Φ2: 0.054% to determine whether it can be used to prepare concrete.

[0082] S06: For sand washing wastewater with Φ<Φ1, it is filtered through a stainless steel screen and then collected and stored for concrete preparation; for sand washing wastewater with Φ1≤Φ<Φ2, it is purified by ion exchange resin and then used for concrete preparation; for sand washing wastewater with Φ≥Φ2, it cannot be used for concrete preparation and needs to be retained in the sand washing pool for cleaning sand and gravel aggregates again and waiting for re-testing.

[0083] In this embodiment, combined with the research on the detection of machine-made sand containing unknown flocculants in previous experiments, sand washing wastewater and pre-treatment samples were obtained according to the description in the specific implementation plan, and it was determined that the pre-treated sand washing wastewater reacted with the copper sulfate standard solution to produce flocculent precipitation, and it was determined that anionic polyacrylamide was contained therein. Further testing obtained current values ​​A1 and A2, as well as the corresponding dropwise solution volumes, as shown in Table 1.

[0084] Table 1 Test current values

[0085]

[0086] Plot Table 1, such as Figure 4 As shown. Calculate and obtain k x The value is -0.144.

[0087] K x Value and Figure 3 Compare with the standard curve in to obtain two concentration values. Figure 5 As shown, when the molecular weight is 18 million, the corresponding concentration value Φ a is 0.021%; when the molecular weight is 2200, the corresponding concentration value Φ b It is 0.015%.

[0088] Then, the detection is performed in the manner of determining the molecular weights of different flocculants in step S043, and the current values ​​A3 and A4 are 3.86 μA and 1.79 μA respectively, indicating that it is 18 million molecular weight polyacrylamide and the concentration is 0.021%.

[0089] According to the threshold values ​​Φ1: 0.018% and Φ2: 0.054%, and the test concentration Φ a It is 0.021%, and it is judged to be sand washing wastewater with Φ1≤Φ<Φ2. After being purified by anion exchange resin, the sand washing wastewater is collected for the preparation of concrete.

[0090] In summary, the present disclosure provides a method and use for detecting the concentration of flocculants in sand washing wastewater and determining the molecular weight. By detecting the water quality of wastewater from sand and gravel aggregate cleaning at the construction site, the influence of the residual amount of flocculants in sand washing wastewater on the water quality is considered, and the quantitative detection of the residual amount of flocculants is achieved by designing supporting detection equipment. On the basis of considering the influence of the concentration of flocculants in aqueous solution on the performance of concrete, it is judged whether the sand washing wastewater can be used to prepare concrete, and a judgment standard is given. Therefore, the present disclosure has at least the following beneficial effects:

[0091] 1. The detection method developed in the present disclosure can detect the molecular weight and concentration of flocculants under the premise of the molecular weight of flocculants in unknown solutions, and can avoid the interference of turbidity, absorbance, impurity ions, etc. on the detection results, and the detection accuracy can be improved to 0.01% of the concentration. Existing methods include testing the viscosity, absorbance, turbidity, etc. of aqueous solutions. The present disclosure is completely different from the existing methods. It innovatively develops the flocculation effect of flocculants on harmful ions or special media, and uses the change of solution conductivity to characterize the concentration change of solutions of known concentrations, and then inverts the unknown flocculant molecular weight and flocculant concentration in the solution, which can promote innovation in the field of water resource detection and recycling.

[0092] 2. The reuse of sand washing wastewater can reduce the cost of concrete production. The recycled water can replace the use of some fresh water resources. At the same time, the recycled water resources can also be put back into production, reducing the purchase and sale costs of raw materials.

[0093] 3. The present invention has made outstanding contributions in saving freshwater resources. It has achieved high-efficiency and high-precision detection of sand washing wastewater at the engineering site, greatly improved the recovery and reuse rate of freshwater resources, fully saved freshwater resources, and also helped to reduce wastewater discharge, which has a positive impact on environmental protection.

[0094] 4. The technical requirements and equipment costs of the disclosed operation are extremely low. Most of the disclosed methods rely on expensive equipment, such as ion chromatographs, spectrophotometers, etc. Only a few high-precision laboratories can meet the testing requirements, and the requirements for operating technicians are extremely high. Therefore, they are not applicable to construction site laboratories. The supporting detection equipment developed in the disclosed invention is low-priced, easy to use, and does not require high technical personnel. It only needs to learn the operation method, and it has good universality.

[0095] 5. This disclosure also provides a post-treatment method for sand washing wastewater that exceeds the detection threshold, which has not been mentioned in similar disclosures. The application of related technologies can further improve the recycling rate of freshwater resources and help build a resource-saving enterprise and an environmentally friendly society.

[0096] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method for detecting flocculant concentration and determining molecular weight in sand washing wastewater, characterized in that: include: S1, preparing indicator standard solution and anionic polyacrylamide standard solutions of different concentrations and different molecular weights; S2, establishing a detection circuit; the detection circuit comprises a first solution pool, a third solution pool, a fourth solution pool, and a second solution pool connected in series in sequence, wherein a power supply is electrically connected to the first solution pool and the second solution pool, respectively, and an ammeter is electrically connected to the first solution pool and the fourth solution pool, respectively; and the fifth solution pool to the eighth solution pool are respectively connected to the pipelines of the first solution pool to the fourth solution pool; S3, using the indicator standard solution, the anionic polyacrylamide standard solution and the detection circuit, obtaining a concentration-slope standard curve; wherein the slope is the slope of the current-filled solution volume curve; S4, pre-treating the sand washing wastewater to be tested, using the detection circuit to obtain the slope to be tested, and then obtaining multiple concentrations; S5, using the anionic polyacrylamide standard solution of multiple concentrations, the sand washing wastewater to be tested and the detection circuit to detect the current, and using the standard curve to determine the molecular weight of the flocculant, and then obtain the flocculant concentration; Wherein, obtaining the concentration-slope standard curve in S3 includes: S31, adding an indicator standard solution, deionized water, deionized water, and deionized water with a volume of V0 to the first solution pool to the fourth solution pool, respectively, and adding an anionic polyacrylamide standard solution with a standard concentration to the fifth solution pool to the eighth solution pool; S32, using a peristaltic pump to uniformly add the standard solutions in the fifth solution pool to the eighth solution pool to the corresponding first solution pool to the fourth solution pool; S33, using the ammeter to detect the current at a certain interval to obtain a concentration-slope standard curve under a standard concentration; S34, repeating the steps S31 to S33 to obtain standard curves at different concentrations and different molecular weights; In S5, the molecular weight of the flocculant is determined by using the standard curve, and then the concentration of the flocculant is obtained, which includes: S51, first empty the liquids in the first solution pool to the fourth solution pool, add the anionic polyacrylamide standard solution of the first concentration among the multiple concentrations to the first solution pool and the third solution pool, add the anionic polyacrylamide standard solution of the second concentration among the multiple concentrations to the second solution pool and the fourth solution pool, and obtain the first current using the detection circuit; wherein the liquid volumes in the four solution pools are the same; S52, adding equal volumes of pretreated sand washing wastewater to be tested into the four solution pools, and obtaining a second current using the detection circuit; S53, if the first current is greater than the second current, which is equivalent to diluting the standard solution of the second concentration, the molecular weight of the flocculant is the molecular weight corresponding to the anionic polyacrylamide standard solution of the first concentration; otherwise, which is equivalent to adding the standard solution of the first concentration, the molecular weight of the flocculant is the molecular weight corresponding to the anionic polyacrylamide standard solution of the second concentration; S54, obtaining the flocculant concentration according to the flocculant molecular weight and the corresponding standard curve; When determining the molecular weight of the flocculant, the concentrations corresponding to the slope values ​​of the same current-added solution volume curve are recorded as the first concentration and the second concentration, and each concentration corresponds to a molecular weight.

2. The method for detecting flocculant concentration and determining molecular weight in sand washing wastewater according to claim 1, characterized in that: The solute in the indicator standard solution in S1 is one or more of copper sulfate, ferric sulfate, ferric chloride, and copper chloride, and the concentration of the indicator standard solution is 1 g / L to 5 g / L; The concentration of the anionic polyacrylamide standard solution in S1 is 0.012%~0.060%, and the molecular weight is 18 million~22 million.

3. The method for detecting flocculant concentration and determining molecular weight in sand washing wastewater according to claim 1, characterized in that: The fifth solution tank to the eighth solution tank in S2 are connected to the first solution tank to the fourth solution tank through hoses and peristaltic pumps respectively.

4. The method for detecting flocculant concentration and determining molecular weight in sand washing wastewater according to claim 3, characterized in that: The detection circuit in S2 further includes a single chip microcomputer for analyzing the concentration of the flocculant.

5. The method for detecting flocculant concentration and determining molecular weight in sand washing wastewater according to claim 1, characterized in that: The peristaltic pump in S32 uniformly adds liquid at a flow rate of 50-100 ml / min.

6. The method for detecting flocculant concentration and determining molecular weight in sand washing wastewater according to claim 1, characterized in that: The preprocessing in S4 includes: The sand washing wastewater to be tested is filtered through at least two stainless steel sieves with different pore sizes in sequence, and the pore sizes of the at least two stainless steel sieves with different pore sizes decrease in sequence.

7. The method for detecting flocculant concentration and determining molecular weight in sand washing wastewater according to claim 1, characterized in that: In S4, obtaining the slope to be measured by using the detection circuit includes: S41, adding the indicator standard solution, deionized water, deionized water, and deionized water with a volume of V0 to the first solution pool to the fourth solution pool, respectively, and adding the pretreated sand washing wastewater to be tested to the fifth solution pool to the eighth solution pool; S42, using a peristaltic pump to uniformly add the sand washing wastewater to be tested in the fifth solution pool to the eighth solution pool to the corresponding first solution pool to the fourth solution pool; S43, using the ammeter to detect the current at certain intervals to obtain a slope to be measured, and then obtain multiple concentrations.

8. An application of the method for detecting flocculant concentration and determining molecular weight in sand washing wastewater according to any one of claims 1 to 7, for determining whether the sand washing wastewater to be tested can be used for preparing concrete according to the determined flocculant concentration and molecular weight.

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