A method for controlling halogenated disinfection byproducts in water with high efficiency and low energy consumption

Abstract

The present invention relates to the field of water treatment, and in particular to a method for controlling halogenated disinfection byproducts in water with high efficiency and low energy consumption. The present invention provides a method for preparing rice straw biochar using renewable resource plant straw as raw material, and the rice straw biochar can efficiently adsorb organic macromolecules such as macromolecular organic matter HA in water. The present invention also provides a method for reducing halogenated disinfection byproducts in water, first using the rice straw biochar to preferentially adsorb NOM macromolecules, and then using activated carbon for further adsorption after disinfection with a chlorine-containing disinfectant, giving full play to the respective advantages of two different carbon materials, not only improving the removal efficiency of halogenated disinfection byproducts and their precursors, but also achieving the safety of drinking water, and having significant effects of energy saving and environmental protection.

Description

Technical Field

[0001] The invention relates to the field of water treatment, and in particular to a method for controlling halogenated disinfection by-products in water with high efficiency and low energy consumption. Background Art

[0002] The excessive presence of natural organic matter (NOM) in the water environment is the main cause of organic pollution in water sources. Humic acid (HA) is the main component of NOM, so the effective removal of HA in water is the key to treating organic pollution. HA is not a single acid, but a complex mixture containing functional groups such as carboxyl and phenolic hydroxyl. Most HA can form aggregates in aqueous solution. Due to its strong chelating effect, it can "organize" many harmful substances. Drinking water contaminated by HA is also one of the main environmental factors causing Kaschin-Beck disease.

[0003] Conventional water treatment units such as coagulation, sedimentation and filtration currently used in China cannot effectively remove HA, resulting in the reaction between chlorine-containing disinfectants and HA to form some disinfection by-products (DBPs) during the disinfection of drinking water with chlorine-containing disinfectants. So far, more than 800 DBPs have been discovered, most of which are cytotoxic, genotoxic, mutagenic, teratogenic or carcinogenic. Halogenated disinfection by-products are a type of DBPs, specifically referring to disinfection by-products containing halogen elements (such as chlorine, bromine, iodine, etc.). Some halogenated disinfection by-products, such as chloroform and dichloroacetic acid, have been listed as carcinogenic substances by the World Health Organization (WHO). HA is also one of the important precursors of halogenated disinfection by-products.

[0004] There are roughly two solutions to remove DBPs. One is to find alternative disinfectants, and the other is to improve water treatment methods. The first is that alternative disinfectants include ozone, potassium permanganate, etc. However, ozone decomposes quickly in water, and the continuous disinfection effect is not as good as chlorine, and the cost is high; in addition, these alternative disinfectants will also cause secondary pollution, and the substances produced are also carcinogenic. The second is improved water treatment methods, including removing DBPs precursors and directly removing generated DBPs. In current water supply facilities, the former solution is usually adopted. The main way to remove DBPs precursors is activated carbon adsorption, among which granular activated carbon is widely used to control DBPs, and its main function is to remove the main precursor NOM before disinfection. Among them, Filtrasorb 400 (F400), as a coal-based activated carbon, is the most typical activated carbon used in the water treatment industry, with a specific surface area of ​​about 1000m 2 / g. The adsorption of NOM mainly utilizes the mesopores (pore size 2-50nm) and macropores (pore size 1-2nm) of activated carbon. However, granular activated carbon contains many micropores, and the adsorption effect on macromolecules is very poor. Macromolecules can easily block the pores on the surface, resulting in limited service life and life of activated carbon columns. According to statistics, more than millions of tons of industrial activated carbon are used for odor removal, hazardous substances and water treatment each year, resulting in a large amount of energy loss.

[0005] Biochar (BC) is a low-cost, renewable carbon material produced from organic raw materials under certain thermal combustion and limited oxygen conditions. It is currently widely used in the adsorption research of dyes, antibiotics, pesticides, and heavy metals. According to relevant calculations, the preparation cost of BC is US$350-1,200 per ton, and the cost of activated carbon is US$1,100-1,700 per ton. Therefore, compared with most activated carbons prepared from fossil energy, low-energy renewable BC has the advantages of lower cost and better energy conservation and environmental protection. However, there is still a lack of research on the use of biochar's adsorption properties to treat organic matter in water before disinfection with chlorine disinfectants to remove disinfection by-products, especially halogenated disinfection by-products and their precursors. Summary of the invention

[0006] In view of this, the present invention proposes a method for preparing rice straw biochar using renewable resource plant straw as raw material, and the rice straw biochar can efficiently adsorb organic macromolecules such as macromolecular organic matter HA in water. On this basis, the present invention also innovatively proposes a method for reducing halogenated disinfection by-products in water. The specific method is to first use the rice straw biochar to preferentially adsorb macromolecules in NOM, and then use activated carbon for further adsorption after disinfection with a chlorine-containing disinfectant, so as to give full play to the respective advantages of the two different adsorption materials, effectively control disinfection by-products, ensure the safety and health of drinking water, and achieve energy-saving effects.

[0007] The technical solution of the present invention is achieved in this way:

[0008] In a first aspect, the present invention provides a method for preparing rice straw biochar, comprising the following steps:

[0009] A1. Dry the rice straw at 105°C to constant weight, then place it in a sealed reactor that is isolated from oxygen and filled with protective gas, slowly heat it from room temperature to a final temperature of 400-800°C at a rate of 8-15°C / min, and continue to burn it in an oxygen-free state for 1-3 hours;

[0010] A2. After cooling to room temperature, the product obtained in step A1 was ground and sieved, then ultrasonically activated for 0-120s, and then dried at 105°C to constant weight to obtain rice straw biochar.

[0011] In some preferred embodiments, in step A1, the reaction conditions in the sealed reactor further include: the flow rate of the protective gas is 30-70 mL / min.

[0012] In some preferred embodiments, in step A2, the powder is ground and then sieved through a 12-40 mesh screen.

[0013] The straw biochar provided by the present invention is selected from different biochar materials, by changing the firing conditions and pretreatment conditions, and comparing the NOM adsorption effect with the granular activated carbon Filtrasorb 400, so as to screen out the most ideal conditions and materials, which are the above-mentioned straw biochar fired at 600-800°C, and more preferably the straw biochar fired at 800°C.

[0014] In the present invention, the rice straw is rice stalks, which refers to the remaining part of rice after the rice seeds are harvested.

[0015] In step A1, the slow heating, oxygen isolation, and introduction of protective gas are adopted to reduce the generation of by-products and improve the yield and quality of the product.

[0016] The ultrasonic activation treatment in step A2 for 0-120 seconds improves the adsorption activity of the biochar, and more preferably the ultrasonic activation treatment is for 30 seconds.

[0017] A second aspect of the present invention provides a rice straw biochar prepared according to any one of the above methods.

[0018] In a third aspect, the present invention provides an application of the rice straw biochar, including application in at least one of the following (1)-(5): (1) reducing halogenated disinfection by-products in water; (2) removing disinfection by-product precursors in water; (3) removing natural organic matter in water; (4) removing humic acid in water; and (5) removing organic halides in water.

[0019] In a fourth aspect, the present invention provides a method for reducing halogenated disinfection by-products in water, comprising the following steps:

[0020] B1. Adding the rice straw biochar according to claim 4 to the water sample to be disinfected, and subjecting the water sample to a constant temperature oscillation treatment;

[0021] B2. Add chlorine-containing disinfectant to the water sample for disinfection, and react under constant temperature of 25-35℃, sealed and light-proof conditions;

[0022] B3. Add activated carbon to the water sample and perform constant temperature oscillation treatment.

[0023] In some preferred embodiments, the method for reducing halogenated disinfection by-products in water further comprises the following steps:

[0024] B4. After the treatment is completed, the rice straw biochar and activated carbon are recovered, and the recovered rice straw biochar and activated carbon can be recycled by repeating the above steps B1-B3.

[0025] In some preferred embodiments, in step B1, the volume mass ratio of the water sample to the straw biochar is V:m=1L:(0.8-1.5)g.

[0026] In some preferred embodiments, in step B3, the volume mass ratio of the water sample to the activated carbon is V:m=1L:(0.8-1.5)g.

[0027] In some preferred embodiments, the reaction conditions in steps B1 and B3 include: constant temperature oscillation temperature 25-35° C., rotation speed 100-200 rpm, and time 1-2 h.

[0028] In some preferred embodiments, in step B2, the chlorine-containing disinfectant includes hypochlorite, the volume mass ratio of the water sample to the chlorine-containing disinfectant is V:m=1L:5mg, the mass of the chlorine-containing disinfectant is calculated according to Cl2, and the time is 2-3h.

[0029] The beneficial effects of the present invention include at least the following:

[0030] 1. The raw materials for preparing the rice straw biochar of the present invention are widely available, and agricultural byproducts are fully utilized to turn waste into treasure, thereby preventing environmental pollution. The rational use of the renewable biochar with lower cost as an adsorption material is helpful for the implementation of the concept of green and sustainable development. In addition, the preparation process and operation of the rice straw biochar provided by the present invention are simple, the preparation is fast, the production cycle is short, no special chemical equipment is required, and industrial production is easy to achieve.

[0031] 2. The method for reducing halogenated disinfection by-products in water provided by the present invention is a new method for synergistically controlling DBPs and their precursors. It preferentially utilizes straw biochar with low specific surface area but large pore size to efficiently adsorb large molecular HA, thereby solving the problems of many micropores in activated carbon, poor adsorption effect on large molecules, and easy clogging of the surface of activated carbon by large molecules, thereby avoiding the limitation of the service life and life of activated carbon due to large molecules.

[0032] 3. The present invention selects rice straw biochar fired at 800°C as the biochar with the best adsorption effect, and cleverly utilizes the complementary effects of biochar and activated carbon. Biochar is preferentially used to adsorb large molecular HA in water, and then disinfects it. After disinfection, activated carbon is used to adsorb smaller molecular disinfection by-products produced after disinfection, which can increase the TOX removal rate by more than 3 times, effectively control the halogenated disinfection by-products in water, and ensure the safety and health of drinking water. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 The HA removal rate results of biochar and activated carbon fired at 400℃ for 2h. In the figure, straw, pine, and bamboo represent biochar fired with dry straw, dry pine, and dry bamboo as raw materials, respectively. AC represents activated carbon (F400). Each carbon material is grouped according to different particle sizes.

[0035] Figure 2 The HA removal results of biochar and activated carbon fired at 600℃ after 2h of adsorption. Each carbon material was grouped according to the different ultrasonic activation time.

[0036] Figure 3 The HA removal results of biochar and activated carbon fired at 800℃ after 2h of adsorption. Each carbon material was grouped according to the different ultrasonic activation time.

[0037] Figure 4 To screen the results of HA removal by biochar and activated carbon sintered at 800℃ for 2h in the experiment and reproduce the results;

[0038] Figure 5 Results of HA removal rates over time for simulated drinking water treated with different carbon materials;

[0039] Figure 6 Distribution diagram of rice straw biochar and activated carbon at pore size of 0-10 nm according to NLDFT&GCMC(ads) algorithm;

[0040] Figure 7 The figures are the measurement results of the residual concentration of total organic halogens (TOX) in simulated drinking water after adsorption and disinfection in different ways; the "★" in (b) indicates the TOX measurement results of 100 mL of new simulated drinking water after the materials used in the "New Method" were recycled and processed in Example 7; the specific corresponding steps are shown in Examples 6-7. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. The reagents not described separately in detail in the present application are all conventional reagents and can be obtained from commercial channels; the methods not described in detail are all conventional experimental methods and can be obtained from the prior art.

[0042] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0043] The terms "including" and "having" and any variations thereof of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment comprising a series of steps is not limited to the listed steps or modules, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products or equipment.

[0044] Experimental instruments and materials

[0045] Vacuum atmosphere tube furnace (GSL-1700X), refrigerated water bath constant oscillator (GTCS-2018), electric blast drying oven (101-1BS), total organic carbon analyzer (TOC-L CSH), ultraviolet spectrophotometer (UV3200), fully automatic specific surface area, micropore and mesopore analyzer (BELSORP-max), total organic halogen analyzer (multiX2500).

[0046] Dry pine wood blocks (1*1*1cm) were purchased from Anji Weiting Home Furnishing Factory; dry straw (about 1m long) was purchased from Jijia Home Furnishing Factory; dry bamboo (1m long*2-3cm thick) was purchased from Dongyang Wood Crafts Factory; F400 activated carbon was purchased from Calgon Carbon Company (Filtrasorb 400) in the United States.

[0047] The configuration of simulated drinking water: 3mg / L HA (concentration calculated according to total organic carbon TOC), 90mg / L NaHCO3 (concentration calculated according to CaCO3) and 2mg / L NaBr (concentration calculated according to Br - calculate).

[0048] Measurement method and calculation formula

[0049] (1) TOC measurement: First, use a total organic carbon analyzer to accurately measure the total organic carbon (TOC) of the prepared HA mother liquor.

[0050] (2) HA measurement: The absorbance at 254 nm (UV 254 ) was used for determination and a standard curve was drawn to quantitatively determine the HA concentration in the water sample.

[0051] (3) The calculation formula of HA removal rate is as follows:

[0052]

[0053] Where, HA removal rate, %; C0 is the HA concentration before treatment; C e is the residual concentration of HA after treatment.

[0054] (4) TOX (total organic halogen) measurement: First, the sample was pretreated by adding 2.4 mL of 1 M nitric acid to every 100 mL of sample to ensure that the sample pH was less than 2. Activated carbon was then used to separate DIX (inorganic halogen) and TOX (organic halogen). The activated carbon and TOX adsorbed on the activated carbon were mineralized into CO2 and DIX by high-temperature combustion at 950°C. Finally, the converted DIX was quantified by the microcoulometric method. That is, the current change caused by the reaction of halogen with silver ions to produce precipitation indicated the concentration of halogen, thereby measuring TOX.

[0055] Example 1 Preparation of rice straw biochar

[0056] The dry rice straw raw material was placed in an electric drying oven at 105°C and dried to constant weight, and then fired in a vacuum atmosphere tube furnace at 400°C, 600°C, and 800°C, with a N2 flow rate of 50 mL / min, a heating rate of 10°C / min from room temperature to the final temperature, and a constant temperature time of 2 h. The fired biochar was then ground and sieved to a suitable particle size, ultrasonically activated, and then placed in an electric drying oven at 105°C and dried to constant weight.

[0057] The present invention aims to screen out raw materials suitable for pyrolysis processes from the widely existing biomass resource library. In view of the application background in the drinking water treatment process, the present invention particularly focuses on the selection of non-toxic, safe and efficient raw materials. When specifically setting the embodiments and comparative examples, the present invention uses straw, pine wood and bamboo as raw materials for further research. In order to avoid possible health risks and process complexity, the present invention explicitly excludes urban organic waste and farm waste with complex ingredients and certain health risks as options for raw materials.

[0058] Comparative Example 1

[0059] The dry straw raw material was replaced with dry pine wood blocks, and the other steps were the same as in Example 1.

[0060] Comparative Example 2

[0061] The dry straw raw material was replaced by dry bamboo, and the other steps were the same as those in Example 1.

[0062] Example 2 Measurement of the adsorption effect of biochar and activated carbon on HA (screening experiment)

[0063] In this example, in order to screen the type of biochar with better adsorption effect than activated carbon, 0.1g biochar or activated carbon and 100mL simulated drinking water sample were used in a conical flask at 30°C and 150rpm constant temperature oscillator for adsorption, and samples were taken after 2h and 1d of adsorption to measure the residual concentration of HA. According to the control of the final firing temperature, sieve aperture, and ultrasonic activation time treatment conditions, different carbon materials were screened (following the single variable principle) to obtain a more ideal biochar material.

[0064] In this embodiment and the following other embodiments, unless otherwise specified, the activated carbon and the biochar referred to have the same particle size.

[0065] The screening test results are as follows Figure 1-3 As shown in the figure, in the screening target biochar experiment, the effects of various biochars and activated carbon were compared. Only the rice straw biochar fired at 600℃ and 800℃ was better than activated carbon. The screening experiment results showed that the rice straw biochar fired at 800℃ was the biochar with the best adsorption effect on HA; the removal rate was about twice that of activated carbon. It can be seen that rice straw biochar fired at 800℃, as a low-cost, environmentally friendly adsorbent, has broad application prospects and potential in water treatment and other fields.

[0066] The screening results show that the ultrasonically activated biochar has a certain improvement in the adsorption effect of HA compared to the unactivated biochar, and the ultrasonic activation time is controlled in 30s-2min, preferably 30s. In the ultrasonic activation process, too long activation time may not be necessary, and may increase energy consumption and cost. The activation time of 30s can ensure the improvement of adsorption effect while maintaining the efficiency and cost-effectiveness of the operation.

[0067] Example 3 Reproduction Experiment

[0068] According to the method in Example 1 and Comparative Examples 1-2, bamboo biochar, straw biochar and activated carbon fired at 800°C were prepared respectively, and all were ultrasonically activated for 30 seconds. Then, 0.1g of the carbon material and 100mL of simulated drinking water sample were placed in a conical flask for adsorption in a constant temperature oscillator at 30°C and 150rpm, and samples were taken after 2 hours of adsorption to measure the residual concentration of HA. Three parallel samples were set for each group.

[0069] Reproduce the experimental results as Figure 4As shown in the figure, the trend is basically consistent with the results of the screening experiment, and the difference between the two removal rates is within 3%. The bamboo biochar has the worst effect, with a removal rate of almost 0 for HA; the straw biochar has the best adsorption effect, with a removal rate of about 24%, which is about twice the removal rate of activated carbon.

[0070] Example 4 Adsorption kinetics study

[0071] Rice straw biochar and activated carbon fired at 600℃ and 800℃ were selected, and each carbon material was divided into two groups, one of which was ultrasonically activated for 30s and the other was not. 0.1g of carbon material was weighed into a 150mL conical flask, 100mL of simulated drinking water was added, and adsorption was carried out in a constant temperature oscillator at 30℃ and 150rpm. The residual concentration of HA was measured at 0.5, 1, 2, 3, 5, 8, 12, 24, 48, 72, 81, and 105h (until adsorption equilibrium), and pseudo-first-order kinetics and pseudo-second-order kinetics were fitted.

[0072] Table 1: Adsorption kinetics fitting results

[0073]

[0074] In Table 1, straw-600 indicates biochar fired at 600°C using rice straw as raw material.

[0075] The experimental results are as follows Figure 5 As shown in the figure, the adsorption removal rate of HA by the six materials changes with time. The adsorption of HA by biochar and activated carbon follows a trend of first fast and then slow. The adsorption amount of rice straw biochar is higher than that of other groups. The difference in adsorption amount in the early stage is larger than that in the later stage. The adsorption amount of the three carbon materials is almost equal at adsorption equilibrium. The adsorption effect of rice straw biochar activated by ultrasound for 30s on HA is improved compared with that of unactivated rice straw biochar.

[0076] The fitting results of pseudo-first-order kinetics and pseudo-second-order kinetics are shown in Table 1. The adsorption of HA by the above carbon materials conforms to pseudo-first-order and pseudo-second-order kinetics. Table 1 compares the correlation coefficients of K1, K2 and the two fitting methods, and the correlation coefficient of pseudo-second-order kinetics is better.

[0077] Example 5 Characterization Tests of Biochar and Activated Carbon

[0078] The specific surface area of ​​rice straw biochar fired at 800 °C was measured by the Brunauer-Emmett-eller (BET) N2 method using a BET pore size analyzer (BELSORP-max). The pore size distribution was calculated by the nonlocalized density functional theory (NLDFT&GCMC(ads)) N2 adsorption / desorption isotherm method.

[0079] Table 2: BET test results of rice straw biochar and activated carbon

[0080]

[0081] In Table 2: A BET Denotes specific surface area, D p represents the average pore size, PV represents the pore volume; the corresponding values ​​of micropores and mesopores represent the percentage of their number in the total value.

[0082] As shown in Table 2, the structural differences between straw biochar (SBC) and activated carbon (AC) fired at 800°C were obtained according to the BET algorithm. The specific surface area of ​​AC is much higher than that of SBC, but the average pore size of AC is slightly smaller than that of SBC, which is consistent with previous research, indicating that the large pore size of SBC is conducive to the adsorption of large molecular HA.

[0083] like Figure 6 The test results show the pore size distribution of SBC and AC. The pore size of SBC is concentrated around 0.8nm, while the pore size of AC is abundant around 0.4nm, 1nm, and 1.5nm.

[0084] Example 6 Application of biochar-activated carbon combined adsorption in reducing halogenated disinfection byproducts in water

[0085] (1) Methods

[0086] The total organic halogen concentration (TOX) was used to characterize the control effect of different groups of schemes on halogenated disinfection by-products. The experiment was divided into 5 groups, namely Simulated Drinking Water group (direct disinfection for 2 hours), Activated Carbon group (AC adsorption for 10 hours + disinfection for 2 hours), Straw Biochar group (SBC adsorption for 10 hours + disinfection for 2 hours), Traditional Method group (AC adsorption for 2 hours + disinfection for 2 hours) and New Method group (SBC adsorption for 1 hour + disinfection for 2 hours + AC adsorption for 1 hour). The details are as follows:

[0087] The specific steps of the SimulatedDrinkingWater group are: :

[0088] In 100mL of simulated drinking water, add an appropriate amount of sodium hypochlorite to ensure that the effective chlorine concentration is 5mg / L. Use pH test paper to quickly measure the pH of the solution to 7.0±0.4. Quickly seal and disinfect at 30℃ for 2h in a dark place, then terminate the disinfection process with an appropriate amount of sodium thiosulfate.

[0089] The specific steps of the Activated Carbon group are:

[0090] Add 0.1g of activated carbon to 100mL of simulated drinking water, and adsorb it in a conical flask at 30℃ and 150rpm constant temperature oscillator for 10h. Then add an appropriate amount of sodium hypochlorite to ensure that the effective chlorine concentration is 5mg / L, and use pH test paper to quickly measure the solution pH to 7.0±0.4. Quickly seal and disinfect in a dark place at 30℃ for 2h, and then terminate the disinfection process with an appropriate amount of sodium thiosulfate.

[0091] The specific steps of the Straw Biochar Set are:

[0092] In 100mL simulated drinking water, add 0.1g SBC (rice straw biochar fired at 800℃) and adsorb for 10h in a conical flask at 30℃ and 150rpm constant temperature oscillator. Then add appropriate amount of sodium hypochlorite to ensure that the effective chlorine concentration is 5mg / L, and quickly measure the solution pH to 7.0±0.4 with pH test paper. Quickly seal and disinfect at 30℃ for 2h in dark conditions, and then terminate the disinfection process with appropriate amount of sodium thiosulfate.

[0093] The specific steps of the Traditional Method group are:

[0094] Add 0.1g of activated carbon to 100mL of simulated drinking water, and adsorb it in a conical flask at 30℃ and 150rpm constant temperature oscillator for 2h. Then add an appropriate amount of sodium hypochlorite to ensure that the effective chlorine concentration is 5mg / L, and use pH test paper to quickly measure the solution pH to 7.0±0.4. Quickly seal and disinfect in a dark place at 30℃ for 2h, and then terminate the disinfection process with an appropriate amount of sodium thiosulfate.

[0095] The specific steps of the New Method group are:

[0096] 1) Add 0.1 g of SBC to 100 mL of simulated drinking water and adsorb it in a conical flask at 30°C and 150 rpm on a constant temperature oscillator for 1 h.

[0097] 2) Add an appropriate amount of sodium hypochlorite to ensure that the effective chlorine concentration is 5 mg / L, and use pH test paper to quickly measure the solution pH to 7.0±0.4. Quickly seal and disinfect at 30°C in a dark place for 2 hours, and then terminate the disinfection process with an appropriate amount of sodium thiosulfate.

[0098] 3) Finally, 0.1 g of activated carbon was added and adsorption was carried out in a conical flask at 30° C. and 150 rpm in a constant temperature oscillator for 1 h.

[0099] (2) Conclusion

[0100] Lower TOX concentrations indicate lower total amounts of halogenated disinfection byproducts in the water and thus lower toxicity. Figure 7As shown in (a), the TOX concentration remaining after 10 h of disinfection by SBC is lower than that of AC, and is also less than half of the TOX concentration in the simulated drinking water without adsorption. It can be seen that the TOX level in the simulated drinking water sample after SBC treatment is significantly reduced. Figure 7 The measurement results of (b) show that the biochar-activated carbon combined adsorption method provided by the present invention improves the TOX removal rate by more than 3 times compared with the traditional activated carbon process.

[0101] contrast Figure 7 (a) and (b), the TOX concentrations of the Straw Biochar group and the New Method group are almost the same, and the New Method group is slightly higher. However, the Straw Biochar group used 0.1g SBC adsorption for 10 hours and then disinfection, while the New Method group used 0.1g SBC adsorption for 1 hour, disinfection, and then 0.1g AC adsorption of the disinfected solution. The Straw Biochar group needed a 12-hour adsorption and disinfection process, while the New Method group only needed 4 hours to complete. In terms of the use of time and the actual application of the water treatment process, the New Method group system showed the best effect.

[0102] Example 7 Application of recovered carbon materials in reducing halogenated disinfection byproducts in water

[0103] The specific steps are as follows:

[0104] (1) Recover the SBC and AC used in the New Method in Example 6.

[0105] (2) Repeat the steps of the New Method in Example 6 and adsorb 100 mL of new simulated drinking water according to the same process.

[0106] like Figure 7 (b) The TOX measurement result corresponding to "★" is the effect of the combined adsorption of the recovered SBC and AC. It can be seen that the combined adsorption of the recovered SBC and AC is still better than the adsorption effect of the first use of AC in the Traditional Method group in Example 6. The experimental results show that the recycled straw biochar and activated carbon materials can still maintain a certain adsorption performance. Therefore, the straw biochar and activated carbon can still be reused after recycling, which helps to reduce processing costs and reduce waste generation.

[0107] In summary, the method for reducing halogenated disinfection by-products in water provided by the present invention is a new method for synergistically controlling halogenated disinfection by-products and their precursors, which combines the respective advantages of biochar and activated carbon, has a simple process, is easy to operate, and has strong feasibility and practicality.

[0108] The present invention preferentially utilizes straw biochar with low specific surface area but large pore size to efficiently adsorb macromolecular HA, solving the problem that activated carbon has many micropores, poor adsorption effect on macromolecules, and macromolecules are easy to block the surface of activated carbon, thereby extending the service life and life of activated carbon. Moreover, this method cleverly utilizes the complementary effects of biochar and activated carbon. First, biochar is used to adsorb macromolecular HA in drinking water, and then disinfection is performed. After disinfection, activated carbon is used to adsorb smaller molecular disinfection byproducts produced after disinfection, which can increase the removal rate of TOX by more than 3 times and effectively control the halogenated disinfection byproducts in drinking water.

[0109] The straw biochar provided by the present invention has low preparation cost and can significantly improve the utilization efficiency of activated carbon. Its raw materials are widely available and renewable, meeting the requirements of environmentally friendly and sustainable development.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reducing halogenated disinfection by-products in water, characterized in that: The steps include: B1. Add rice straw biochar to the water sample to be disinfected and perform constant temperature oscillation treatment; B2. Add chlorine-containing disinfectant to the water sample for disinfection, and react under constant temperature of 25-35℃, sealed and light-proof conditions; B3. Add activated carbon to the water sample and perform constant temperature oscillation treatment; The method for preparing rice straw biochar comprises the following steps: A1. Dry the rice straw at 105°C to constant weight, then place it in a sealed reactor that is isolated from oxygen and filled with protective gas, slowly heat it from room temperature to a final temperature of 400-800°C at a rate of 8-15°C / min, and continue to burn it in an oxygen-free state for 1-3 hours; A2. After cooling to room temperature, the product obtained in step A1 was ground and sieved, then ultrasonically activated for 30-120 seconds, and then dried at 105° C. to constant weight to obtain rice straw biochar.

2. The method according to claim 1, characterized in that In the step A1, the reaction conditions in the sealed reactor also include: the flow rate of the protective gas is 30-70 mL / min.

3. The method according to claim 1, characterized in that In the step A2, the powder is ground and then sieved through a 12-40 mesh screen.

4. The method according to claim 1, characterized in that: The following steps are also included: B4. After the treatment is completed, the rice straw biochar and activated carbon are recovered, and then the recovered rice straw biochar and activated carbon are recycled by repeating steps B1-B3.

5. The method according to claim 1, characterized in that In the step B1, the volume mass ratio of the water sample to the straw biochar is V:m=1L:(0.8-1.5)g; in the step B3, the volume mass ratio of the water sample to the activated carbon is V:m=1L:(0.8-1.5)g.

6. The method according to claim 1, characterized in that The reaction conditions in steps B1 and B3 include: constant temperature oscillation temperature 25-35° C., rotation speed 100-200 rpm, and time 1-2 h.

7. The method according to claim 1, characterized in that In step B2, the chlorine-containing disinfectant includes hypochlorite, the volume mass ratio of the water sample to the chlorine-containing disinfectant is V:m=1L:5mg, the mass of the chlorine-containing disinfectant is calculated according to Cl2, and the reaction time is 2-3h.

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