Low cost corncob interface evaporator for salt directional deposition and method of making same

Abstract

The present application relates to a low-cost corncob interface evaporator for salt directional deposition and a preparation method thereof, and the preparation method comprises the following steps: S1, soaking corncobs in a metal ion solution to allow the metal ions to penetrate into the corncobs; S2, taking out and drying, and then transferring to an oven at 200 DEG C for pre-oxidation for 1 h; S3, carbonizing in an oxygen-free and low-temperature environment; S4, cleaning the carbonized corncobs and drying to obtain the corncob interface evaporator. The prepared corncob interface evaporator has low energy consumption and low cost, and can make salt directionally deposit on the corncob shell.

Description

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a low-cost corncob interface evaporator with directional salt deposition and a preparation method thereof. Background Art

[0002] High-salinity wastewater (such as desulfurization wastewater from thermal power plants, landfill leachate, and reverse osmosis concentrate from seawater desalination) is difficult to treat and produces large volumes of wastewater. Traditional treatment technologies, such as membrane and thermal evaporation, suffer from high energy consumption and costs. Therefore, there is an urgent need for a low-energy, low-cost high-salinity wastewater treatment technology.

[0003] Solar-driven interfacial evaporation, due to its simplicity and environmental friendliness, holds great promise as a promising method for treating high-salinity wastewater. However, salt deposition on the evaporator surface during interfacial evaporation significantly reduces light absorption and vapor escape, significantly reducing the efficiency and lifespan of the solar evaporator. To mitigate salt deposition during evaporation, numerous complex interfacial evaporators have been designed.

[0004] Compared to complex interfacial evaporators, leveraging the structural characteristics of natural biomass to construct an interfacial evaporator that avoids salt deposition offers advantages such as simplicity, environmental friendliness, and low cost. Corncobs, as a byproduct often discarded in large quantities, offer advantages such as low cost and easy availability. While some work on corncob evaporators has been conducted, these suffer from high carbonization temperatures (biomass carbonization typically requires 600–1000°C) and high energy consumption. Furthermore, the corncob structure has not been manipulated, hindering the controlled and directional deposition of salt.

[0005] Therefore, it is very necessary to invent a low-cost interface evaporator with directional salt deposition to achieve continuous interface evaporation of high-salt wastewater. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a low-cost corncob interface evaporator with directional salt deposition, which has the characteristics of low energy consumption, low cost and directional salt deposition.

[0007] To this end, the present invention provides a low-cost corncob interface evaporator with directional salt deposition, the preparation process of which includes the following steps:

[0008] S1, soaking the corn cob in a metal ion solution to allow the metal ions to penetrate into the corn cob;

[0009] S2, take out and dry, and transfer to a 200 °C oven for pre-oxidation for 1 h;

[0010] S3, then carbonize in an oxygen-free, low-temperature environment;

[0011] S4, washing and drying the carbonized corn cob to obtain a corn cob interface evaporator;

[0012] The low temperature mentioned above refers to a temperature lower than 600-1000°C required for general carbonization, and here refers to a temperature lower than or equal to 500°C.

[0013] In some embodiments of the present invention, the specific operation of step S1 is: placing the corn cob in 0.01~0.5molL -1 The metal ion solution is ultrasonicated for 0.5 to 2 hours and then allowed to stand for 0.5 to 12 hours.

[0014] In some embodiments of the present invention, the metal ion solution is selected from at least one of FeCl3 and NiCl.

[0015] In some embodiments of the present invention, the specific operation of step S3 is: carbonizing the pre-oxidized corn cob at a temperature of 200-500° C. for 2-4 hours, more preferably at a temperature of 200° C. for 4 hours.

[0016] In some embodiments of the present invention, the prepared corncob interface evaporator has a heterogeneous structure, wherein the inner core is a large-pore structure and the outer shell is a small-pore structure, the inner core transmits water quickly and the outer shell transmits water slowly.

[0017] In some embodiments of the present invention, the water transport of the corncob interface evaporator pre-impregnated with metal ions is much higher than that of the corncob interface evaporator not impregnated with metal ions.

[0018] In some embodiments of the present invention, the water transmission rate ratio between the inner core and the outer shell of the corncob interface evaporator pre-impregnated with metal ions is higher than that of the corncob interface evaporator not pre-impregnated with metal ions.

[0019] In some embodiments of the present invention, the corncob interface evaporator pre-impregnated with metal ions generates interconnected nanofibers due to the activation of the metal ions.

[0020] The present invention provides the following advantages: the corncob interfacial evaporator offers the advantages of low cost and controllable salt deposition. Utilizing the catalytic effect of metal ions, the corncob can be activated at low temperatures, enabling the fabrication of the interfacial evaporator with low energy consumption. The heterogeneous structure of the corncob core and husk, combined with metal ion activation, enhances the differential water transport between the core and husk, enabling directional salt deposition on the husk. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] Figure 1 Photo of corn cob.

[0023] Figure 2 This is a photo of corn cob carbonized at 200℃.

[0024] Figure 3 This is a photo of the carbonization of corncob pre-soaked in FeCl3 solution at 200℃.

[0025] Figure 4 This is a photo of corn cob carbonized at 400℃.

[0026] Figure 5 This is a scanning electron microscope image of a corncob pre-impregnated with FeCl3 solution and carbonized at 200°C.

[0027] Figure 6 Photo of directional deposition of evaporator salt on the interface of pre-infiltrated FeCl3 carbonized corncob.

[0028] Figure 7 Photo of salt deposition in the evaporator at the interface of carbonized corncob at 400°C.

[0029] Figure 8 Graph showing water transfer rates of the corncob core and husk. Implementation Method

[0030] The present invention will be described in detail below.

[0031] Example 1

[0032] The corncob was placed in a 200℃ oven for pre-oxidation for 1 h, and then carbonized at 200℃ in a N2 atmosphere for 4 h to obtain a corncob interface evaporator. The corncob steam interface evaporator was brown, as shown in Figure 2. Figure 2 shown.

[0033] Example 2

[0034] Soak corn cobs in 0.5 mol L -1 The FeCl3 solution was ultrasonically shaken for 0.5 h and then allowed to stand for 12 h. After being taken out, it was dried in a 60 °C oven and transferred to a 200 °C oven for pre-oxidation for 1 h. It was then carbonized at 200 °C in a N2 atmosphere for 4 h to obtain Fe 3+ Modified corncob evaporator, Fe 3+ The modified corncob evaporator appears black, e.g. Figure 3 As shown, the microstructure Figure 5 shown.

[0035] Example 3

[0036] The corncob was placed in an oven at 200 °C for pre-oxidation for 1 h, and then carbonized at 400 °C for 4 h in a N2 atmosphere to obtain a corncob interface evaporator. The corncob steam interface evaporator appeared black, as shown in Figure 2. Figure 4 shown.

[0037] Example 4

[0038] Prepare 20 wt% NaCl solution, place the corn cob evaporator prepared in Example 2 on the interface of 20 wt% NaCl solution for evaporation, and as the water evaporates, salt is controllably and directionally deposited on the outer shell of the corn cob, as shown in FIG. Figure 6 shown.

[0039] Example 5

[0040] Prepare 20 wt% NaCl solution, place the corn cob evaporator prepared in Example 3 on the interface of 20 wt% NaCl solution through foam evaporation, and as the water evaporates, salt is deposited on the entire surface of the corn cob, as shown in FIG. Figure 7 shown.

[0041] Example 6

[0042] Using polystyrene foam as a support, a highly consistent corncob evaporator was floated on a 1 mol L -1 Place a pH test paper on the top surface and record the color change area and time of the pH test paper to characterize the water transmission properties of various corn cob cores and shells, such as Figure 8 shown.

[0043] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a low-cost corncob interface evaporator with salt directional deposition, characterized in that: Soak corn cobs in 0.5 mol L -1 The FeCl3 solution was ultrasonically shaken for 0.5 h and then allowed to stand for 12 h. After being taken out, it was dried in a 60 ° C oven and transferred to a 200 ° C oven for pre-oxidation for 1 h. It was then carbonized at 200 ° C in a N2 atmosphere for 4 h to obtain Fe 3+ Modified corncob evaporator, Fe 3+ The modified corncob evaporator appears black.

2. The corncob interface evaporator prepared by the method for preparing a low-cost corncob interface evaporator with directional salt deposition according to claim 1 is characterized in that The corncob interface evaporator has a heterogeneous structure, wherein the inner core has a large-pore structure and the outer shell has a small-pore structure; the inner core transmits water quickly, while the outer shell transmits water slowly; the corncob interface evaporator contains carbon nanofibers; the corncob interface evaporator increases the water transmission rate of the inner core and the outer shell, and the ratio of the water transmission rate of the inner core to the outer shell also increases; during the evaporation process of the corncob interface evaporator, salt ions will preferentially deposit on the outer shell of the corncob and fall off under gravity.

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