Treatment of wastewaters containing acid, reactive and direct dyes using aminosilane functionalized silica

Abstract

Aminosilane modified silica was prepared and investigated for the adsorption of textile dyes such as C.I. Acid Orange 7(AO7), C.I. Reactive Black 5 (RB5) and C.I. Direct Blue 71 (DB71) from aqueous media and wastewaters. The values of the sorption capacities obtained from the Langmuir isotherm model were: 5.3 mg g-1, 58.7 mg g-1 and 72.2 mg g-1 for AO7, DB71 and RB5, respectively. The affinity series of the dyes for the modified silica can be presented as follows: C.I. Reactive Black 5 > C.I. Direct Blue 71> C.I. Acid Orange 7. The influence of anionic surfactant (SDS) and sodium chloride on dye sorption was investigated in a system containing 100 mg L-1 dye and 0.1-1 g L-1 SDS or 1-2 5 g L-1 NaCl. The sorption capacities decrease with increasing concentration of SDS in the solution. Retention of AO7 and RB5 was reduced in the presence of NaCl. A satisfactory agreement of the experimental data with the pseudo second-order kinetic model was found. Effectiveness of the aminosilane modified silica in raw textile wastewater purification was confirmed.