Removal of direct dyes from aqueous solution by adsorption onto the mangrove charcoal activated by microwave-induced phosphoric acid

Abstract

This study describes the enhanced adsorption capacity of modified mangrove charcoal (MMC) using microwave irradiation with the diluted acid H3PO4 for removal of direct dyes including direct yellow 132, direct blue 71, and acid blue 193 from aqueous solution. Affecting parameters such as pH, contact time, and temperature were investigated. Results showed that the adsorption of direct dyes was favorable at acidic conditions and at 100 min contact time to reach the adsorption equilibrium. Adsorption kinetic study suggested that the adsorption process of direct dyes onto MMC was well described via pseudo-second-order model. For equilibrium thermodynamic studies, it was found that the adsorption process followed the Freundlich isotherm model. Thermodynamic studies indicated that adsorption reaction of direct dyes onto MMC was an endothermic and spontaneous process.