Preparation of humic acid-bentonite polymer composite: A heavy metal ion adsorbent

Adsorbents for wastewater treatment have evolved from scientific adsorbents to natural adsorbents. In this study, a humic acid-bentonite polymer (HBP) composite comprising humic acid, bentonite, and anionic polyacrylamide was integrated into an anionic polyacrylamide (aPAM) polymer matrix as an adsorbent pellet with N, N-methylene-bis-acrylamide (MBA), sodium tetraborate pentahydrate and chromium chloride is used as a novel adsorbent to remove Ni(2+), Cd(2+) and Pb(2+) ions from aqueous solution. Sorption of these ions onto HBP is studied as a function of pH, adsorbent dosage, initial metal ion concentration, humic acid, and bentonite properties to evaluate adsorption efficiency. The results showed that adsorption sharply depends on pH, metal ion concentration, and contact time, but is complemented by humic acid and bentonite properties. The adsorption increased from 8% to 94.7% in the first 30 min at respective pH values of 5.6 and 9 for (Ni(2+), Cd(2+), and Pb(2+)). The HBP sorption power decreased with increasing adsorbent dosage, while the adsorption efficiency increased in ascending order for the cations Pb(2+), Ni(2+) and Cd(2+) with efficiencies up to 94.7%, 90.9%, and 90.2%. The experimental data for Ni(2+), Pb(2+) adsorption fits the Langmuir isotherm, while that for Cd(2+) adsorption fits the Freundlich isotherm. HBP showed modest adsorption performance at low and high concentrations, this is attributed in large part to the humic acid and bentonite properties that affect HBP's unique performance.