Adsorption of Cr(VI) from Aqueous Solutions on Organic Modified Laponite

Laponite was synthesized by hydrothermal method and modified by cetyltrimethyl ammonium bromide(CTMAB). The adsorption of Cr(VI) on modified laponite(CTMABL) as a function of pH, CTMABL dosage, ionic strength, contact time, and temperature was studied via batch technique. The results showed that the specific surface area and pore volume of modified samples were decreased, while the average pore size was increased. The d((001)) value of CTMABL raised from 1.23 nm to 1.79 nm after the modification, which in. dicated that the CTMAB had entered into the interlayer of laponite. The removal of Cr(VI) from solution in. creased with the increase of solution pH value. At pH<8.5, the surface Zeta potential of CTMABL particles is positive, and thus the adsorption efficiency can be promoted by the electrostatic attraction between CTMABL particles and Cr(VI) anions. The adsorption of Cr(VI) on CTMABL increased with the increase of adsorbent dosage, maintaining a removal efficiency of >99% at the dosage of 4 g/L. The effect of ionic strength on the adsorption of Cr(VI) was not obvious. The adsorption kinetic data of Cr(VI) on CTMABL were well described by the pseudo. second. order kinetics model, and the adsorption rate was influenced by the membrane diffusion and intra. particle diffusion. The adsorption isotherms of Cr(VI) on CTMABL can be described well by the Langmuir model. The thermodynamic parameters of Cr(VI) adsorption on CTMABL at different temperatures indicated that the adsorption was endothermic and spontaneous. The adsorption of Cr(VI) was dominated by surface complexation, whereas electrostatic attraction could also promote the Cr(VI) adsorption on CTMABL.