Cationic dye removal using surface treated activated carbon as an adsorbent

Abstract

The use of treated activated carbon (AC) is investigated to eliminate cationic dye malachite green (MG) using modelled dye solution. Anionic surfactant sodium lauryl sulfate modified AC (SLS-AC) and AC treated with other two surfactants viz. sodium dodecyl sulfonate and hexadecyl trimethyl ammonium bromide were used for the analysis. Optimum SLS-AC was analyzed and characterized using BET, XRD, ESEM accompanied with XEDS, FTIR, HR-TEM and zeta potential measurement which confirms the sorption of MG onto SLS-AC. The influence of the starting dye concentration, pH, adsorbent dose, interaction time, and additive salts as well as actual water samples were investigated. The presence of NH⁴⁺, Ca²⁺, Mg²⁺, Na²⁺, Ca²⁺ and K⁺ cations in dye solution showed a negligible (less than 5%) influence on the dye removal capacity. The study of kinetics showed that apart from the best fitted pseudo second order rate, intra particle diffusion also played its part in the sorption system. Isotherm studies accompanied with error analysis revealed that the Langmuir isotherm (q_max = 217.6 mg g⁻¹) controls the adsorption equilibrium. The adsorption reaction was favourable with the rise in temperature hinting at an endothermic system. Column experimental data were verified with several models showing the fitness of the Thomas model. The reusability (no. of cycles) of the used adsorbent was studied using regeneration experiments. Analysis inferred that AC modified using surfactants can be adopted effectively for enhanced adsorption capacity of dyes from aqueous solution and also not much work has been reported on the use of anionic surfactant modified AC for the dye removal process.