Efficient adsorption of cationic and anionic dyes on Algerian natural phosphate

Abstract

Adsorption is now recognized as an effective and economic method for wastewater treatment. Thus, in recent years, development of low cost adsorbent for dye loaded wastewater remediation has become an important area of research. Algerian phosphate was tested as an effective adsorbent for the removal of cationic dye methylene Blue (MB) as well as the anionic dye blue bezaktiv S-GLD 150 (BB) from synthetic wastewater. The phosphate was characterized by XRD, FT-IR, TGA, SEM, EDX and BET analysis. pHPZC analysis was performed to determine pH sensitive adsorptive removal of cationic and anionic dyes. Batch adsorption experiments of the dyes from aqueous solution were conducted, taking into account the influence of initial dye concentration (10–500 mg/L), adsorbent dosage (1–6 g/L), contact time (5–120 min) and solution pH ((2–12) ± 0.2). The experimental results show that, the adsorption was pH dependent with a high adsorption capacity of MB in basic range and high adsorption of BB in the acidic range. Experimental adsorption data were modeled by different equilibrium isotherms such as Langmuir, Freundlich, Redlich Peterson and Sips. The adsorption process fitted well to pseudo-second-order kinetics and the Langmuir model. The calculated maximum adsorbed quantity qmax of MB and BB were found 30.61 (mg/g) and 20.78 (mg/g) successively. The adsorption process was found to be exothermic in nature in the case of the MB and endothermic for BB. Accordingly; the phosphate has been shown to be a very efficient and low-cost adsorbent, and a promising alternative for eliminating dyes from industrial wastewater.