Alginate/clinoptilolite beads as a novel adsorbent for reducing the salinity of industrial wastewater: adsorption kinetics and isotherm study

Abstract

ABSTRACT Treatment and desalination of unconventional water are considered important alternatives to combat water scarcity in Tunisia. This study demonstrates a viable approach to the increasing possibility of the salinity reduction of industrial effluent through adsorption. In this work, a novel alginate complex was developed for reducing the salinity of the industrial wastewater to be reinjected and reused again within the industrial process and even in agriculture. The Calcium alginate/clinoptilolite beads (Ca-Alg/Clino beads) were prepared using sodium alginate (2%) solution and calcium chloride (4%) solution as the crosslinking agent with clinoptilolite. Batch experiments were carried out to test the adsorption capacity of the synthetised Ca-Alg/Clino beads. It was found that the salinity reduction process depends strongly on the pH, the adsorbent mass, the interaction time, and the initial salt concentration. The highest reduction efficiency and salinity reduction were achieved at pH (6-7). Batch adsorption experiments indicated that Ca-Alg/Clino beads allow an excellent salinity reduction of up to 96.83% for a dosage adsorbent/water of 2 g/L and a salinity of 6 g/L at a contact time of 20 min. The maximum adsorption capacity (qmax) was 30.1 mg/g. The optimal adsorption pH was 7. The adsorption isotherms data follow well the Langmuir model. The separation factor, RL = 0.74, indicates that the adsorption process is favourable. The kinetics data favour the pseudo-second-order model. The fabricated beads can be reused 5 times without any weight loss. This material has excellent efficiency when applied to real environmental water.