Adsorption Behavior of Cr(VI) from Aqueous Solutions by Microwave Modified Porous Larch Tannin Resin

Larch tannin resin (LTNA) was prepared by a microwave modified cross-linking reaction. The adsorption of chromium(VI) from an aqueous solution by LTNA was studied using batch adsorption experiments. LTNA has a large number of pores, the size of which are about 250 nm. After adsorption, the internal structure of the LTNA resin assumed an obvious three-dimensional network. The adsorption of Cr(VI) on LTNA was investigated as a function of pH, dose of adsorbent, and adsorption time. The results indicated that the removal of Cr(VI) was pH-dependent. The optimum adsorption was observed at pH 1.0, and the maximum adsorption capacity was 9.134 mg/g. The Cr(VI) adsorption by the LTNA gel obeyed the Langmuir adsorption isotherm. The kinetic processes of Cr(VI) adsorption onto LTNA could be acceptably explained by the pseudo-second order kinetic rate model. Thermodynamic parameters revealed the spontaneity and exothermic nature of adsorption. Desorption of adsorbed Cr(VI) was successfully realized with a 0.1 M NaOH solution.