Adsorption removal of cationic dyes from aqueous solutions by raw and chemically activated cedar sawdust
Zineb Bencheqroun, Imane El Mrabet, Mostafa Nawdali, Mohammed Bénali, Hicham Zaitan
Abstract
ABSTRACT The aim of this work is to study the removal of Basic Blue 3 (BB3) and Methylene blue (MB) from aqueous solutions using raw and chemically treated cedar sawdust as eco-friendly and sustainable bioadsorbents. The raw and treated cedar sawdust (CS) samples were activated with NaOH (0.1 N) and HCl (0.1 N) solutions. The surface characteristics of the bioadsorbents were analyzed by diverse physico-chemical methods such as scanning electron microscopy with energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, point of zero charge (pH pzc ), X-ray diffraction. The monitoring of the optimal experimental conditions of the different parameters such as dye concentration, contact time, adsorbent dose and solution pH were performed in a batch system. Experimental results show that the adsorption process is rapid and reaches equilibrium after 1 h of contact time. The adsorption capacities of the CS bioadsorbent depend on the pH of the solution and adsorbent dose. Consequently, the adsorption of BB3 and MB is favored at basic pH with the maximum adsorption percentage removal of 98% for BB3 and 99.8% for MB. Adsorption kinetics and equilibrium isotherm parameters were fit using two classic adsorption models (Langmuir and Freundlich). The adsorption kinetics of dyes onto CS followed could be described well with the pseudo-second-order model, whereas the equilibrium data fitted well to the Langmuir isotherm model with a correlating constant (R 2 ) higher than 0.98. The maximum adsorption capacities (Q max ) onto of raw-CS, HCl-CS and NaOH-CS were estimated to be 47.62, 71.94 and 76.92 mg g –1 for MB and 33.67, 72.46 and 85.3 mg g –1 for BB3 respectively, showing that the NaOH-CS adsorbent is about 1.6–2.6 time more efficient that the natural-CS. As a result, chemically treated cedar sawdust has great potential as an inexpensive and readily available alternative bioadsorbent for the removal of cationic dyes from industrial wastewaters.