Adsorption Modeling of Cr^+3 on Volcanic Tuff-Based Geopolymer

In the current work, geopolymer was synthesized from volcanic tuff and was then used as a sorbent for cr^+3 from aqueous solutions. an adsorption batch experiment was conducted to study the factors affecting the adsorption process. the obtained results showed a high removal efficiency of geopolymer (96 %) against 70 % for the volcanic tuff with an uptake capacity of 21.24 and 14.76 mg/g for both materials, respectively. the removal efficiency increased with increasing the ph up to 5, geopolymer dosage, contact time up to thirty minutes, temperature, and the decrease of cr^+3 initial concentration in the studied ranges. the validity of the isotherm models to the experimental data can be ranked in the order of langmuir > temkin > frundilch > dubinin–radushkevich. the kinetic study showed that the second order model provided the best fit with r^2 of 0.97 against 0.44 and 0.62 for the first order and the intra-particle model. the sorption process can be described as endothermic, monolayer, physical, and of a high ion affinity to the surface of the geopolymer. the results obtained buttressed the applicability of using a volcanic tuff-based geopolymer for the cr^+3 removal as a low-cost natural material at low concentrations.