The Treatment Of Dye Wastewater Using Bentonite

Because of its low price, large surface area and cation exchange capacity,bentonites can be used as adsorbent and flocculation agent in wastewater treatment.The dye wastewater treatment methods and the applications of bentonites in this fieldare systematically reviewed in the first part of this dissertation. Then the adsorptionperformance of cationic dye on bentonite and on active carbon are compared, and theadsorption of2-naphthol on beonites after the adsorption of CTMAB and CV areexamined. The influence of the coexisting pollutants on the removal efficiency ofeach other are discussed. The main original conclusions of this work are as follows:1. Compare with active carbon, the bentonite adsorption is a much lower costtechnological method for cationic dye wastewater treatment. Through hightemperature carbonization and acidification treatment, beonites after the adsorption ofcationic dye can be an effective adsorbent toward organic pollutants. The adsorptioncapcity of cationic dye on bentonite is1.5times that of active carbon, combined withadsorption performance and market prices, the cost of bentonite adsorption is10%that of active carbon. Through high temperature carbonization and acidificationtreatment, beonites after the adsorption of cationic dye have good sorption to2-naphthol.2. It is found that the CTMA and CV are adsorbed together within the interlayerspace and form relatively large organic aggregates, which can serve as sorptionmedium for HOCs. The basal spacings of the organoclays after water saturation or notindicates that only small amount of water molecules can enter the interlayer spaces oforganoclays after the adsorption of CTMAB and CV. Under wet condition, CTMAcan promote the expansion while CV may hinder the expansion at their relatively highloading level. It is interesting that the adsorbed CTMAB and CV produce synergy toadsorption of2-naphthol on bentonites. When the concentration of2-naphthol within200mg·L^-1, the removal efficiency of it is very high, such as the removal efficiency of2-naphthol on the bentonite after the adsorption of0.4CEC CTMAB and0.4CEC CVreach up to98%.3. It is found that bentonite can effectively remove variety of coexistingpollutants in cationic dye wastewater. The influence of the coexisting pollutants onthe removal efficiency of each other are discussed. The results shows that bentoniteshave good sorption to CTMAB、CV and2-naphthol, and the coexistence pollutantsCTMAB and CV produce synergy to adsorption of2-naphthol on bentonites. When the wastewater contain0.6CEC CTMAB、0.4CEC CV and the concentration of2-naphthol within200mg·L^-1, bentonite is a good kind of adsorbent to this threepollutants, the removal efficiency of them is99%、99%、90%respectively. Thesorption amount of2-naphthol on the bentonite in the presence of0.6CEC CTMABand0.4CEC CV is bigger than that combination of the bentonite in the presence of0.6CEC CTMAB and the bentonite in the presence of0.4CEC CV.