Performance study of a low-cost adsorbent - raw date pits - for removal of azo dye in aqueous solution.

The feasibility of using natural waste (raw date pits) as a low-cost adsorbent for the adsorption of an anionic dye (Congo red) from aqueous solution has been investigated. Adsorption optimized conditions were obtained at low dose 1 g/L, initial dye concentration 100 mg/L, pH 2, equilibrium contact time 120 min, and temperature 20 °C. The corresponding adsorption capacity was around 70 mg/g and could reach 150 mg/g by increasing the ionic strength of the dye solution (0.05 M CaCl2). These results are well modeled by Freundlich isotherm and kinetics study followed by pseudo second-order model. Thermodynamic parameters indicate that the adsorption process is endothermic and not spontaneous. The tests of desorption-regeneration showed that the studied adsorbent has the disadvantage of the loss of efficiency at its reuse but this is offset by its abundance. Based on these results, it can be used as competitive material for the removal of dyes.