Modification And Adsorption Properties Of Alkaline Sludge From Soda Plant

At present, there have accumulated stockpiles of more than100million tons alkali sludge, which has seriously polluted our environment. The treatment and disposal of alkali sludge have become the focus of environmental protection industry. With the rapid development of textile industry and dyestuff industry, the environmental problems, causing from textile and dyestuff industry, have become increasingly prominent. Adsorption method has been playing an important role in the field of wastewater treatment, because of its efficiency, simplicity, and cheapness. As had a specific surface area, negatively charged and fine particles, alkali sludge can use as an adsorbent.Firstly, the adsorption of methylene blue by alkali sludge was studied, which used the experiments of adsorption kinetics and adsorption isotherm. The experimental results show that:adsorption of methylene blue independents on pH(pH=3～11), in reverse, the decolorization rate of methylene blue is increased as the increase of temperature and dosage. The adsorption equilibrium time is180min, which is constant when the dosage and temperature changed. The process of methylene blue uptake onto alkali sludge follows the psuedo second-order rate expression and the intraparticle diffusion model. The adsorption rate was controlled by chemical adsorption and intraparticle diffusion.The experimental datas for methylene blue system fit the Freundlich isotherm model. Dubinin—Radushkevich model shows that the adsorption of methylene blue is an ion exchange adsorption. Thermodynamic studies show that the adsorption of methylene blue is spontaneous, endothermic and degrees of freedom increased process, which includes physical adsorption and chemisorption.Alkali sludge was modified by sodium dodecyl sulfate and the optimum modification conditions was determined using the orthogonal experiment method. The experimental results show that:the optimum modification conditions are6h,1CMC(a critical micelle concentration is about2360mg/L),30℃. After modified, the point of zero charge is decreased from5.20to3.23. In the experimental conditions, the adsorption equilibrium time is60min, decolorization rate is98.8%, which is higher than unmodified alkali sludge. The adsorption rate of modified alkali sludge is greater than the unmodified, and is increased with the increase dosage. The process of methylene blue uptake onto modified alkali sludge follows the psuedo second-order rate expression, and the adsorption rate is controlled mainly by chemical adsorption. The experimental datas for methylene blue system fit the Langmuir isotherm model. Dubinin—Radushkevich model shows that the adsorption of methylene blue is an ion exchange adsorption. Thermodynamic studies show that the adsorption of methylene blue is spontaneous, endothermic and degrees of freedom increased process, which includes physical adsorption and chemisorption.The results of this study show that alkali sludge and modified alkali sludge, as an adsorbent, can effectively remove methylene blue dye from wastewater. The results not only provide a new way for comprehensive utilization of alkali sludge and the selection of adsorbent of dye, but also has broad application prospects and better environmental benefit since it can treat waste by waste.