Abstract
A vast array of industrial waste products, agricultural by-products, and biological materials, such as bacteria, algae, yeasts, and fungi have received increased attention for heavy metal removal and recovery due to their good performance, low cost, and availability in large quantities. Such materials are cheaper, more effective alternatives to commercial activated carbon (AC) for the removal of heavy metals from aqueous solution. The authors review in greater detail the various factors affecting the adsorption capacity and cost efficiency based on the literatures and present research results. Special emphasis has been made on nature of the precursors, their pretreatment and modification, the activation conditions of time and temperature, pH of aqueous media, and regeneration/reuse potential. The authors present some of the latest important results and give a source of up-to-date literature on the ACs prepared from various low-cost precursors from agro-industrial wastes as well as from biological materials. The evolution of adsorption has turned from an interesting alternative approach into a powerful standard technique by offering a numbers of advantages: better performance in terms of ulterior adsorption capacity, rate of adsorption, solving wastewaters pollution in a cost-effective way, and overcoming part of the solid wastes problem around the world. Various advantages and challenges have been identified and a widespread and great progress in this area can be expected in the future.