Sustainable Remediation of Heavy Metals through Agricultural Waste-Derived Adsorbents

Abstract

Heavy metals (HMs) are known to be non-biodegradable and non-metabolic agents, hence detrimental to human health. Then, innovative and novel techniques must be formulated to mitigate and remove these contaminants. Several HMs removal techniques are expensive, have low removal efficiency, produce secondary pollutants, and require high operational energy. The adsorption technique has solved these drawbacks, especially when low-cost and naturally available adsorbents derived from agricultural wastes are used. Reviewed papers show that the adsorption of HMs by these adsorbents depends on pH, contact time, temperature, adsorbent dosage, adsorbent particle size, HM ion concentration, agitation speed, and interfering ions. Removal efficiency ranged between 61 and 100% with contact time between 20 and 240 min and pH of 3–10. The adsorption process was well described by pseudo-second-order and Langmuir models. Also, thermodynamic studies revealed endothermic or exothermic processes depending on the type of agricultural waste material, adsorption factors, and adsorption conditions.