Application of kaolin-Fe3O4 nano-composite for the removal of azo dye from aqueous solutions

Kaolin-Fe 3 O 4 nanoparticles synthesized by co-precipitation and hydrothermal methods was used to remove Acid Red 14 (AR14) from aqueous solutions at various pH, dye concentrations, adsorbent dosages, temperatures and ionic strength. Efficient coating of Fe 3 O 4 nanoparticles onto Kaolin was identified by FT-IR, XRD, SEM, EDX and VSM analysis. Removal efficiency of AR14 by Kaolin-Fe 3 O 4 nanoparticles was greater than that by Kaolin-alone and Fe 3 O 4 -alone. Maximum adsorption was obtained at pH 3. The removal efficiency was increased with increasing adsorbent dosage, but was decreased with increasing initial AR14 concentration and temperature. Removal efficiency of AR14 decreased in the presence of four selected anions. Adsorption kinetic was well described by pseudo-second order model. Adsorption isotherm was well described by the Langmuir equation. Maximum adsorption capacity was 94.34 mg/g. Thermodynamic studies indicated adsorption of AR14 onto kaolin-Fe 3 O 4 nanoparticles through an exothermic process. Adsorption activity of AR14 by kaolin- Fe 3 O 4 nanoparticles was maintained even after six successive cycles. Kaolin-Fe 3 O 4 can be used for the treatment of aqueous solutions containing dyes as an efficient adsorbent and can be easily separated from solution by magnet after reaction.