| Hydrogels are a kind of functional polymer materials with three-dimensional network structure, they don’t dissolve in the water, but they can have a high degree of swelling via absorbing a lot of water in the water. The hydrogel adsorption in wastewater treatments has attracted a large number of attention with their advantages, such as low cost, high efficiency, low energy consumption and good regeneration etc, and it is considered to be the most practical technology. The structure of lignocellulose-g-acrylic acid/montmorillonite (P(LNC-g-AA/MMT)) hydrogel and lanthanum chloride modified lignocellulose-g-acrylic acid/montmorillonite (La/P(LNC-g-AA/MMT)) hydrogel were analyzed by Fourier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transimission electron microscope (TEM), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) in this paper. The effects of swelling time, swelling temperature, pH and ion concentration on swelling properties of P(LNC-g-AA/MMT) hydrogel and (La/P(LNC-g-AA/MMT)) hydrogel were studied. The effects of initial concentration of methylene blue (MB) and fuchsin basic (FB) solution, adsorption time, adsorption temperature, pH of dye solution on the adsorption capacities of La/P(LNC-g-AA/MMT) hydrogel for dye were investigated, and the adsorption kinetics and adsorption isotherm models were determined. The effects of HC1 concentration, desorption time and desorption temperature on the desorption rate of La/P(LNC-g-AA/MMT) hydrogel were explored under the optimum adsorption conditions. The cycle regeneration properties of La/P(LNC-g-AA/MMT) hydrogel were explored.The main research results of this paper were summarized as follows:1. The microstructure of P(LNC-g-AA/MMT) hydrogel and La/P(LNC-g-AA/MMT) hydrogel were determined by characterization methods, the characterization results show that:lignocellulose-g-acrylie acid destroys the crystal structure of montmorillonite, La3+ is participated in the polymerization reaction, and the nanocomposite hydrogel with the intercalated-exfoliated structure is formed.2. The effects of swelling time, swelling temperature, pH and ion concentration on swelling properties of P(LNC-g-AA/MMT) hydrogel and (La/P(LNC-g-AA/MMT)) hydrogel were studied The results show that:the swelling ratio of P(LNC-g-AA/MMT) is 43.5 in the distilled water at 30℃ for 120 minutes, and the swelling ratio of La/P(LNC-g- AA/MMT) is 87.9 in the distilled water at 70℃ for 120 minutes. Both of hydrogels are sensitive to pH, and their swelling ratio decreased rapidly when there is Na2SO4 ion in the external environment.3. The effects of adsorption parameters such as initial concentration of dye solution, adsorption time, adsorption temperature, pH of dye solution on the adsorption capacities of La/P(LNC-g-AA/MMT) hydrogel for dye were studied. The results show that:the adsorption capacity of MB on La/P(LNC-g-AA/MMT) hydrogel is 2393.9mg/g, after using the initial concentration of MB solution is 3000mg/L at 30℃ and the pH of 5 for 120 minutes, the adsorption capacity of FB on La/P(LNC-g-AA/MMT) hydrogel is 2787.2mg/g, after using the initial concentration of FB solution is 3700mg/L at 30℃ and the pH of 5.5 for 120 minutes. The adsorption of MB and FB on La/P(LNC-g-AA/MMT) hydrogel are both better accord with pseudo-second-order models and Langmuire isotherm models, and the adsorption process is spontaneous, exothermic and decreased randomness.4. The effects of desorption parameters such as HCl concentration, desorption time and desorption temperature on the desorption rate of La/P(LNC-g-AA/MMT) hydrogel were studied. The results show that:the desorption rate of MB on La/P(LNC-g-AA/MMT) hydrogel is 69.97%, after using the concentration of HCl solution is 0.05mol/L at 30℃ for 20 minutes, the desorption rate of FB on La/P(LNC-g-AA/MMT) hydrogel is 72.48%, after using the concentration of HCl is 0.05 mol/L at 30℃ for 120 minutes with a thermostatted shaker. The results of cycle adsorption and desorption show that, the desorption rate of MB and FB is 57.83% and 63.27% when the cycle adsorption and desorption time of La/P(LNC-g-AA/MMT) hydrogel is 3.5. The effects of adsorption parameters such as MB and FB mixed dyes initial concentration ratio, initial concentration of dye solution, adsorption time, adsorption temperature, pH of mixed dye solution on the adsorption capacities of La/P(LNC-g-AA/MMT) hydrogel for mixed dyes were studied. The results show that:the adsorption capacity of MB and FB in the mixed dyes on La/P(LNC-g-AA/MMT) hydrogel is 1456.2mg/g and 2013.2mg/g, after using the mixed dyes initial concentration ratio is 1:1, the mixed dyes initial concentration is both 3400mg/L at 30℃ and pH of 5 for 120 minutes.6. The effects of desorption parameters such as HCl concentration, desorption time and desorption temperature on the desorption rate of mixed dyes on La/P(LNC-g-AA/MMT) hydrogel were studied. The results show that:the desorption rate of MB and FB in the mixed dyes on La/P(LNC-g-AA/MMT) hydrogel is 61.83% and 67.93%, after using the concentration of HCl is 0.05 mol/L at 30℃ for 120 minutes with a thermostatted shaker. |
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