层状双金属氢氧化物去除废水中重金属的研究

In view of the water quality characteristics of the existence of various metal ions in desulfurization waste water from coal-fired power plant, the removal effect and mechanism of layered double hydroxides(LDHs)on heavy metals were studied by using simulated wastewater. In this paper, two kinds of LDHs heavy metal adsorbents, Friedel salt (Fs)and Ettringite(Ett), were prepared by coprecipitation method. The effects of their dosage, initial pH of wastewater and coexisting ions in wastewater on the removal of heavy metals were investigated. The adsorption mechanism of LDHs on heavy metals was explained in combination with kinetic study. The experimental results suggested that, when the mass concentration of Ett and Fs was 0.15 g/L and 0.07 g/L respectively, the removal rates of Zn(Ⅱ), Cd(Ⅱ), Pb(Ⅱ)and Cr(Ⅵ)in simulated wastewater could reach more than 90%. When the initial pH of wastewater was more than 5.0, the removal rate of heavy metals was ideal, which was more than 80%, and the optimal pH was 9.0. The coexisting ions in the simulated wastewater interfered with the removal of heavy metals by LDHs, but the residual amount of heavy metals in the wastewater could meet the DL/T 997-2020 by increasing the dosage of adsorbent. LDHs could quickly adsorb heavy metal cations through surface precipitation and isomorphic substitution, and heavy metal anions could be effectively removed through surface adsorption and interlayer ion exchange.