Adsorption ability of activated carbons from Phoenix dactylifera rachis and Ziziphus jujube stones for the removal of commercial dye and the treatment of dyestuff wastewater

Abstract

The activated carbons were prepared from Phoenix dactylifera rachis (PRAC) and Ziziphus jujuba stones (JSAC) using chemical activation by H3PO4. Then, they applied to eliminate a commercial reactive dye BEZAKTIV Red S-Max (BRSM). The resultant carbons PRAC and JSAC were characterized by N2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), thermo gravimetric analysis (TGA), scanning electron microscopy (SEM) and Boehm titration method. The BET apparent surface area of the PRAC and JSAC was 1283 and 1896 m2/g, respectively, with predominance acidic character. The effects of initial dye concentration and contact time, pH and temperature on the adsorption were investigated, and it was showed that the elimination percentage decreases as the initial concentration increases, but it rose with the temperature. The experimental equilibrium data were studied using Langmuir, Freundlich and Temkin models, and it was found that the Langmuir model described well the BRSM adsorption (R2 ≥ 0.96), showing a maximum adsorption capacity of BRSM onto PRAC and JSAC of 196.08 and 37.04 mg/g, respectively. The BRSM adsorption kinetic was examined by pseudo-first-order, pseudo-second-order, elovich and intraparticle diffusion models, and it was showed that BRSM adsorption onto used carbons followed pseudo-second-order. The obtained thermodynamic parameters indicated that the phenomenon is spontaneous and endothermic. In addition, the thermal regeneration of the examined carbons revealed that they can be reused on adsorption test. Finally, the results indicated that the Phoenix dactylifera rachis carbon could be considered as low cost material for the elimination of BRSM dye and dyes from dyestuff wastewater (DW).