Adsorption Of Zn (Ⅱ) From Aqueous Solution By Attapulgite

With the widely application of the zinc, it is inevitable to discharge a lot of wastewatercontaining zinc, zinc wastewater is harmful on the environment and human health，it istoxicity, serious pollution and difficult treatment.In this paper, we made the attapulgite of Jingyuan (Gansu) purification and acid-thermalmodification, to adsorb Zn(Ⅱ) in aqueous solution. Experimental conditions as follows:1)quantitative: pH value is5; Dosing quantity of20g/L.2) variables: temperature gradient(25、30、40、50、60℃); Initial concentration (20、40、60、100、150、200mg/L).We analysis the experimental data using the dynamic model，isothermal adsorption model andthe thermodynamic model, to discuss the adsorption of Zn(Ⅱ) onto attapulgite and themechanism of the purification and acid-modified attapulgite, as well as the effect oftemperature, initial concentration on adsorption.Results indicate that:1) The effect of adsorption temperature on attapulgite is not obvious, as the temperatureincreases slightly, the quantity of adsorption increases, and the high initial concentrationincreases relatively obvious compared to the low initial concentration;2) The effect of initial concentration is obvious, with the increase of initial concentration,the quantity of adsorption increases obviously;3) The kinetic study indicates that the adsorption fits the pseudo-second-order process,and does not comply with the pseudo-first-order process and the diffusion model.4) The adsorption was well fitted by the Freundlich adsorption isotherm model, showedthat the adsorption of Zn(Ⅱ) onto attapulgite is not just a simple monolayer adsorption on thesurface, at the same time there is no uniform adsorption and multilayer adsorption, This is aprocess combined chemical adsorption with physical adsorption.5) Thermodynamic analysis indicates that the change in the Gidds free energy is negativeand the enthalpy is positive, it indicates that the adsorption is a spontaneous and endothermiccomplex process.6) Through the contrast analysis of three kinds of mineral on the different adsorptionperformance, we found that the adsorption quantity of Zn(Ⅱ) onto attapulgite is Similar in20、40、60mg/L of low concentration, and the purification and modification of mine onadsorption performance are slightly better than the untreated. On the contrary, the differenceadsorption performance of the three kinds of mineral is more and more big in the higher initialconcentration of solution, the attapulgite modified on adsorption capacity of Zn(Ⅱ) is the strongest, followed by purification one, the untreated is worst, so it is productive to improvethe adsorption performance of attapulgite by purification and acid-thermal modification.