Abstract
Municipal and industrial wastewaters, manufacturing of electrical and electronic equipment, etc., are spreading toxic heavy metals such as lead, arsenic, zinc, nickel, cadmium, uranium, and mercury in the aquatic and soil environment. There are some traditional treatment technologies to remove heavy metals from drinking water and wastewater. However, conventional treatment technologies are expensive and not always efficient for the treatment of wastewaters with high metal concentration. Furthermore, these methods need more chemicals and energy and produce toxic sludge. By contrast, bioremediation by biosorption process using biosorbents is a low-cost, highly efficient, easy operating, eco-friendly, and sustainable green technology for the removal of heavy metals from wastewater. The renewable biocomposite biosorbent materials can be prepared from plant biomass; agricultural wastes such as fruit peels, straw, and coconut coir; bacteria; yeasts; fungi; and algae. The main mechanisms of biosorption process involve ion exchange, surface complexation, adsorption, absorption, and precipitation methods. Biosorption has several benefits, such as selective removal of metals, biosorbent regeneration and metal recovery, rapid kinetics of adsorption and desorption, and no sludge generation. The biosorbent materials can be modified by different physical and chemical treatments and other treatments to prepare novel adsorbents and remove nanoparticle heavy metal contaminants from wastewater. The biosorbents without treatment have shown low adsorption capacity. The chemical pretreatments significantly improved the adsorption capacities of biosorbents by increasing the number of binding sites, ion-exchange ability, and new functional groups. The main composition of plant biomass and agricultural waste consists of cellulose, hemicellulose, and lignin containing different functional groups, such as hydroxyl groups, acetamido, carboxyl, phenolic, structural polysaccharides, amido, amino, sulfhydryl and carboxyl groups, alcohols, and ester. Some important physical and chemical factors influencing the biosorption of heavy metals from wastewater are pH, temperature, initial heavy metal concentration, biosorbent dose, biosorbent size, ionic strength, and coions. Nanoparticle heavy metals can be recovered from the biosorbents by physical treatment such as heating, stirring, and agitation or chemical treatments. The chemical treatments use the chemicals as eluents that include acid, alkali, and organic solvent.
Published Version
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