Surface Modification of Naturally Available Biomass for Enhancement of Heavy Metal Removal Efficiency, Upscaling Prospects, and Management Aspects of Spent Biosorbents: A Review

Abstract

Heavy metal pollution in water emerges as a severe socio-environmental problem originating primarily from the discharge of industrial wastewater. In view of the toxic, non-biodegradable, and persistent nature of most of the heavy metal ions, remediation of such components becomes an absolute necessity. Biosorption is an emerging tool for bioremediation that has gained momentum for employing low-cost biological materials with effective metal binding capacities. Even though biological materials possess excellent metal adsorption abilities, they show poor mechanical strength and low rigidity. Other disadvantages include solid-liquid separation problems, possible biomass swelling, lower efficiency for regeneration or reuse, and frequent development of high pressure drop in the column mode that limits its applications under real conditions. To improve the biosorption efficiency, biomasses need to be modified with a simple technique for selective/multi-metal adsorption. This review is intended to cover discussion on biomass modification for enhanced biosorption efficiency, mechanism studies using various instrumental/analytical techniques, and future direction for research and development including the fate of spent biosorbent. In most of the previously published researches, difficulty of the process in scaling up has not been addressed. The current article outlines the application potential of biosorbents in the development of hybrid technology integrated with membrane processes for water and wastewater treatment in industrial scale.

Adhesive Stalks of DiatomDidymosphenia geminataas a Novel Biological Adsorbent for Hazardous Metals Removal

“…Polysaccharides themselves [7,8] as well as polysaccharidecontaining biomass [9][10][11][12][13][14][15][16][17] are considered excellent adsorbents for harmful metal ions. [18,19] Exceptional adsorptive properties of polysaccharides are mainly attributed to: (i) high hydrophilicity of the polymer due to the hydroxyl groups of glucose units; (ii) the presence of a large number of functional and reactive groups (like acetamido, primary amino, hydroxyls or sulfonates group); and (iii) flexible structure of the polymer chain, [20] and its facile modification.…”

Immobilized microbial biosorbents for heavy metals removal

“…One of the most commonly used natural carriers for immobilization is sodium alginate with crosslinking agent CaCl 2 due to the high biocompatibility and simple gelatinization, although calcium alginate is sensitive to the presence of Na and/or K ions in the solution. Immobilization with natural polymeric carriers leads to the formation of gel particles, a major drawback being diffusion restrictions [23,33]. Immobilization with natural polymeric carriers leads to the formation of gel particles, a major drawback being diffusion restrictions [23,33].…”

“…[23,24]. Microbial biosorbents are characterized by small size and low density, insufficient mechanical stability and low elasticity.…”

“…Immobilized biomass is easily regenerated, can be used repeatedly and incorporated into fixed and fluidized bed columns [23,25]. Immobilized biomass is easily regenerated, can be used repeatedly and incorporated into fixed and fluidized bed columns [23,25].…”

“…In dynamic flow mode biosorption, difficulties arise in liquid-solid phase separation, sorbent swelling and clogging, low regeneration rate, etc. [23,24].…”