Second, the application of bentonite in wastewater treatment
Bentonite is mainly used as adsorbent and flocculant in wastewater treatment. As early as the 1930s, Olin et al. Have used bentonites in the treatment of water and wastewater. In recent years, the application of bentonite in wastewater treatment is more active. Zhang Caiyun , Jiang Yin Shan, respectively, with bentonite adsorption of heavy metals in water treatment; Xia Haiping  and other studied bentonite adsorption kinetics of heavy metal ions; Bev eridge et al  studied the adsorption of bentonite clay and other heavy metals Ions, the results show that when the concentration of nonionic surfactant in aqueous solution is greater than 0.1% (W / V) will significantly affect the adsorption of montmorillonite, cationic surfactants can reduce the impact of montmorillonite on metal ions Adsorption, while the addition of anionic surfactants can improve the removal of heavy metals in water. Gao Tingyao  studied the montmorillonite adsorption of benzene, toluene and ethylbenzene in water; Zhang Caiyun  also treated with bentonite adsorption of phenol in wastewater; Zhao Dongyuan  will be natural montmorillonite adsorption printing and dyeing 9%. Wastewater, the decolorization rate of acid cation dye up to 90%, COD removal rate of 96.9%. Zhang et al.  used bentonite flocculants to treat monosodium glutamate wastewater; Xia Haiping et al.  also used bentonite to treat ammonia nitrogen in coking wastewater. Montmorillonite can also be used to adsorb organic compounds such as quinoline in water [25,26]. Na rine et al.  showed that the adsorption capacity of bentonite to paraquat, fenugreek, and clarithromycin exceeded the cation exchange capacity (CEC), while the adsorption capacity of methylene blue, neo methylene blue and malachite green was equivalent In its CEC.
Because bentonite has the properties of expansibility, dispersion and suspension in water, the original treatment with bentonite is ineffective when the waste water is treated. In particular, the solid-liquid separation speed is slow and the flocculant dehydration effect is poor, affecting its practical application. As a result, people use bentonite - coagulant wastewater treatment to further enhance the removal effect and solid-liquid separation speed. Hang et al  used bentonite adsorption-flocculation method to treat Pb2 +, Cd2 + and Cr (Ⅲ) in wastewater, that is, the treatment of heavy metals in waste water with bentonite-polyaluminum chloride (PAC) The removal rate of 93.1%. Hangzhou Hu et al.  also used bentonite adsorption-flocculation method to treat organic dyes in wastewater, and studied the adsorption characteristics of natural bentonite on cationic, dispersive, reduced, neutral, active and direct organic dyes. It was found that bentonite adsorbed-flocculated The decolorizing effect of the dye aqueous solution was 40% ~ 200% higher than the simple flocculation method. The 0.01% bentonite was added with 0.005% polyaluminum chloride (PAC)
Cationic dye-based printing and dyeing wastewater decolorization rate of 94% - 100%. Wang Zemin, et al  Using diatomite-bentonite composite scavenger to treat straw-based papermaking wastewater, COD removal efficiency is more than 71%, which has the advantages of simple operation, fast dehydration of flocs, short treatment period and low cost. Zhang Jishu et al.  theoretically studied the flocculation effect of hydrolyzed polyacrylamide (HPAM) and poly-aluminum hydroxychloride (PACS) on the sodium montmorillonite suspension. The results showed that the flocculant was more effective than the single- When the effect is significant.