A comparative study of malachite green removal from an aqueous solution using raw and chemically modified expanded perlite

Adsorption of malachite green (MG) from an aqueous solution onto unexpanded perlite (UP), expanded perlite (EP) and NaOH-modified unexpanded perlite (NaOH-UP) powders has been investigated. The effects of contact time, pH, initial dye concentration, adsorbent dosage and temperature have been evaluated. The adsorbents were characterized by Brunauer-Emmett-Teller (BET) analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The obtained results proved that the three examined powders can be used successfully for removal of MG from aqueous solutions as low cost mineral adsorbents. The maximum adsorption capacities of UP, EP and NaOH-UP were 23.81 mg/g, 29.41 mg/g and 39.68 mg/g, respectively. Kinetic studies show that the kinetics of the MG adsorption onto the adsorbents followed the second order model. The MG equilibrium adsorption data were best described by the Langmuir isotherm model for all adsorbents.
Highlights
•An easily available low-cost mineral (Perlite) is modified for adsorption.
•Chemically modified perlite was used to remove malachite green from an aqueous solution for the first time.
•Modified adsorbents were characterized by FTIR and SEM analyses.
•Adsorption kinetics, isotherm and effects of the influential parameters were studied.