Removal of methylene blue and safranin orange pollutants from liquid effluents by soy residue

Abstract

Methylene blue and safranin orange dyes, which are used in the textile and pharmaceutical industries, can severely damage the environment and human health. This study investigated the use of okara residue as an alternative biosorbent for the removal of methylene blue and safranin orange dyes. Substantial amounts of okara residue are generated daily during the processing of soy milk in the agro‐industrial sector. Dye adsorption was not affected by pH. An adsorption study identified the optimal experimental conditions as: 298 K, 0.03 g of adsorbent in 30 mL of dye solution at a concentration of 50 mg L−1, and a contact time of 300 min for methylene blue dye, and 298 K, 0.02 g of adsorbent in 30 mL of dye solution at a concentration of 50 mg L−1, and a contact time of 200 min for safranin orange dye; the maximum adsorption capacities were 93.201 ± 0.01 and 184 592 ± 0.02 mg g−1, respectively. Okara has considerable advantages over other natural materials as an alternative for the treatment of industrial effluents. Because it is easily obtained and does not require any physicochemical treatment, adsorption does not require any specific operation temperature. In addition, okara exhibited a high adsorption capacity compared to other natural materials that require chemical and physical processing for adsorbent preparation.