Adsorption Of Ni (Ⅱ) From Aqueous Solution By Attapulgite

In this paper, we made the attapulgite of Jing Yuan (Gansu) purification andacid-thermal modification, to adsorb Ni(Ⅱ) in aqueous solution. Experimental conditions asfollows:1) quantitative: pH value is6; Dosing quantity of20g/l. variables: temperaturegradient (25,30,40,50,60℃); Initial concentration (20,40,60,100,150,200mg/l). Weanalysis the experimental data using the dynamic model，isothermal adsorption model and thethermodynamic model, to discuss the adsorption of Ni(Ⅱ) onto attapulgite and themechanism of the purification and acid-modified attapulgite, as well as the effect ofadsorption time,temperature, initial concentration on adsorption.Results indicate that:1) The effect of Adsorption time is significantly, as the growth ofthe time, the adsorption capacity increased significantly, especially modified and purifiedattapulgite;2) The effect of adsorption temperature on attapulgite is not obvious, as thetemperature increases slightly, the quantity of adsorption increases, and the high initialconcentration increases relatively obvious compared to the low initial concentration;3) Theeffect of initial concentration is obvious, with the increase of initial concentration, thequantity of adsorption increases obviously;4) The kinetic study indicate that the adsorptionfits the pseudo-second-order process, and does not comply with the pseudo-first-order processand the diffusion model.5) The adsorption of natural、modified and purified attapulgite werewell fitted by the Langmuir adsorption isotherm model, The adsorption of purified attapulgitewell fitted by the Freundlich adsorption and D-R isotherm model, showed that the adsorptionof Ni(Ⅱ) onto attapulgite is not just a simple monolayer adsorption on the surface, at thesame time there is no uniform adsorption and multilayer adsorption, This is a processcombined chemical adsorption with physical adsorption.6) Thermodynamic analysisindicates that the change in the Gidds free energy () is negative and the enthalpy () ispositive, it indicates that the adsorption is a spontaneous and endothermic complex process;7)By the same initial concentration, the adsorption rates of original attapulgite are no significantdifferences under different adsorption time. The adsorption rate differences of purifiedattapulgite and modified attapulgite are more significant with the increase of adsorption time.The different pretreatment attapulgite adsorption rates show a trend of increase with theincrease of adsorption time, and the adsorption rates are significant differences. Theadsorption rates of purified attapulgite are higher than the adsorption rates of modifiedattapulgite; both are significantly higher than the adsorption rates of original attapulgite. Thedifferent pretreatment attapulgite adsorption rates are significantly differences by the increaseof initial concentration, the values of adsorption rates gradually decreases. For different initial concentrations of Ni(Ⅱ), the adsorption equilibrium time of different pretreatment attapulgitegradually increase by the increase of initial concentration.