Removal of two anionic reactive textile dyes by adsorption into MgAl-layered double hydroxide in aqueous solutions

Textile dyes pose a significant challenge for water pollution due to the poor degradability of their complex aromatic structures (e.g., RR-120 and RBB-150). In order to minimize the harmful effects of RR-120 and RBB-150, the capacity of MgAl-layered double hydroxide for removing of these contaminants was studied herein. Batch adsorption experiments were conducted to investigate the effect of various operating parameters, such as solution pH, contact time, dye concentration, and temperature in order to provide optimal conditions for removal. Structural and morphological analyses were used to highlight the assembly and/or interaction LDH-dye. The state of equilibrium of RR-120 and RBB-150 adsorption was pH- and temperature-dependent and followed the pseudo-second-order rate model. Also, the equilibrium adsorption data of both dyes were found to adopt the Langmuir type isotherm model, which assumes a monolayer arrangement in LDH-dye. Furthermore, the effects of four major coexisting and competing mono- and divalent interlayer anions, such as NO₃^-, Cl^-, CO₃^2-, and SO₄^2-, on the uptakes of RR-120 and RBB-150 were studied and the results showed that NO₃^- anions had insignificant effect on the uptakes of RR-120 and RBB-150 by MgAl. An equivalent study on the presence of both dyes in competitive trial adsorption/desorption from binary aqueous solution was investigated. And finally, the reuse operation of recovered material after dye adsorption was tested in up to 5 cycles of recyclability.