Decontamination of Colored Wastewaters Using Natural Sorbents

The capacities of natural sorbents in removing of dyes from synthetic wastewater have been investigated. The investigated sorbents were two natural wood samples (silver fir and beech) for the removal of two disazo direct dyes derived from 4,4\'-diamonibenzanilide (PDP and, RDC). The effects of the support\'s nature, the dose of natural fibres, initial concentration, and temperature on the dye removal were investigated. The obtained results showed a better retention capacity of Beech sawdust. The quantity of dye absorbed per unit of dry natural support decreased, but the efficiency of the dye adsorption (removal percentage) increased when the weight of fibre was doubled. By reducing the apparent area of the fibre the adsorption capacity of natural fibres increased. The uptake of the studied dyes increased with the increase in initial dye concentration and with the decrease in the size of the dye molecules. In order to explain the effect of temperature on the dyes adsorption the experiments were conducted at 298, 313, and 333 K. The adsorption decrease with an increase in temperature indicated that the process is exothermic in nature. Kinetics of adsorption obeyed second order rate equation in case of using investigated sorbents. The best isotherm model that fits the experimental data with lower error was the Sips isotherm model.