Activated Tea Waste as a Potential Low-Cost Adsorbent for the Removal of p-Nitrophenol from Wastewater

The aim of this work was to determine the potential of activated tea waste (ATW) as a useful adsorbent for the removal of p-nitrophenol (p-NP) from aqueous systems. The study was realized using batch experiments with synthetic wastewater having a p-NP concentration of 1000 mg center dot L-1. The effects of pH, contact time, and presence of anions were investigated. An increase in the pH to above neutrality resulted in a decrease in the p-NP adsorption capacity. The adsorption process reached equilibrium within 5 h of contact time. The Freundlich, Langmuir, Temkin, Dubunin-Radushkevich, and Redlich-Peterson adsorption models were used for mathematical description of the adsorption equilibrium, and it was found that the experimental data fitted very well to the Langmuir isotherm. Batch adsorption studies, based on the assumption of a pseudo-first-order, pseudo-second-order, or intraparticle diffusion mechanism, showed that the kinetic data followed closely a pseudo-second-order rather than a pseudo-first-order mechanism. The adsorption capacity of ATW for the removal of p-NP was found to be 142.85 mg center dot g(-1). These results clearly indicate the efficiency of activated tea waste (ATW) as a low-cost adsorbent for treatment of wastewater containing p-NP.