Evaluating the Efficiency of Cadmium Removal by Alginate Hydrogels from Water Using 5,7-Dibromo-8-hydroxyquinoline as a Complexing Reagent

Abstract

Cadmium toxicity in wastewater is a rising concern due to industries like batteries, metallurgy, electroplating, plastic stabilizers, and pigments. The quantitative detection of Cd2+ and its remediation from wastewater samples are of major concern from an environmental point of view. In the present work, an effective spectrophotometric method has been reported using 5,7-dibromo-8-hydroxyquinoline (DBHQ) as a complexing agent for Cd2+. This method has advantages like using recyclable, less toxic solvents and easy sample preparation. The limit of detection, limit of quantification, and sensitivity of the proposed method were found to be 33.30, 36.70 mg L–1, and 2 × 10–3, respectively. The DBHQ method was validated using atomic absorption spectroscopy, and the recovery percentage was more than 98%. These results indicate that DBHQ can be effectively used for monitoring Cd2+ in aqueous systems. The method developed was further employed for monitoring Cd2+ adsorption on calcium alginate (AL) hydrogels. Batch adsorption studies were done to optimize parameters of Cd2+ removal using AL hydrogels, and the data obtained were used for kinetic and thermodynamic studies. Kinetic studies indicated that the pseudo-first-order model showed better fitting, and thermodynamic studies showed Freundlich-like adsorption. The maximum adsorption capacity of Cd2+ on AL hydrogels was found to be 56.45 mg g–1. The validation studies of DBHQ were performed using statistical analysis methods like t-tests and one-way variance.