Polysaccharides as Support for Microbial Biomass-Based Adsorbents with Applications in Removal of Heavy Metals and Dyes

Abstract

The use of biosorbents for the decontamination of industrial effluent (e.g., wastewater treatment) by retaining non-biodegradable pollutants (antibiotics, dyes, and heavy metals) has been investigated in order to develop inexpensive and effective techniques. The exacerbated water pollution crisis is a huge threat to the global economy, especially in association with the rapid development of industry; thus, the sustainable reuse of different treated water resources has become a worldwide necessity. This review investigates the use of different natural (living and non-living) microbial biomass types containing polysaccharides, proteins, and lipids (natural polymers) as biosorbents in free and immobilized forms. Microbial biomass immobilization performed by using polymeric support (i.e., polysaccharides) would ensure the production of efficient biosorbents, with good mechanical resistance and easy separation ability, utilized in different effluents’ depollution. Biomass-based biosorbents, due to their outstanding biosorption abilities and good efficiency for effluent treatment (concentrated or diluted solutions of residuals/contaminants), need to be used in industrial environmental applications, to improve environmental sustainability of the economic activities. This review presents the most recent advances related the main polymers such as polysaccharides and microbial cells used for biosorbents production; a detailed analysis of the biosorption capability of algal, bacterial and fungal biomass; as well as a series of specific applications for retaining metal ions and organic dyes. Even if biosorption offers many advantages, the complexity of operation increased by the presence of multiple pollutants in real wastewater combined with insufficient knowledge on desorption and regeneration capacity of biosorbents (mostly used in laboratory scale) requires more large-scale biosorption experiments in order to adequately choose a type of biomass but also a polymeric support for an efficient treatment process.

Polysaccharides Used in Biosorbents Preparation for Organic Dyes Retaining from Aqueous Media

“…Microbial cells can be used for the removal of pollutants from aqueous effluents through biosorption, a passive process that implies inactive biomass able to adsorb toxic substances on its surface [1,2]. Nonliving biomass of bacteria, fungi, or algae are potential biosorbents, as they are relatively abundant and inexpensive (results as by-product in industrial fermentation) [3][4][5]. Advantages of using inactive biomass include having no nutrients or energy requirements, better sorption capacity, rapid processes, and no toxic effects of the contaminants on the cells.…”

“…Immobilization of microorganisms can overcome these downsides. By immobilization through different techniques using natural polysaccharides, including alginate, chitosan, starch, and cellulose, better-suited biosorbents (easier to handle, reusable, more stable and robust) can be obtained [4,6].…”

“…The types and the number of pollutants that are being removed through biosorption are consistently expanding, including metals, dyes, antibiotics and other pharmaceuticals, and persistent organic pollutants (Lindane, 2,4-Dichlorophenol, 2-Chlorobiphenyl, Pentachloro-nitrobenzene) [1][2][3][4][5]. Biosorption using microbial biomass processes is influenced by several physiochemical parameters, such as pH, temperature, biomass dosage, initial pollutant concentration, contact time, type of pollutant, and type of biosorbent [11].…”

Composites Based on Natural Polymers and Microbial Biomass for Biosorption of Brilliant Red HE-3B Reactive Dye from Aqueous Solutions

“…An important alternative is biosorption-a cost-effective, simple, reversible, passive accumulation process by which inactive biosorbent binds (through ion exchange, absorption, adsorption and surface complexation) certain ions or molecules from aqueous solutions. The advantages of biosorption include: simplicity, no nutrient requirements for the non-living biomass, low sludge generation, low operational costs and high efficiency [1][2][3][4][5][6].…”

“…The use of microorganisms in environmental depollution technologies can be carried out with them either in a free form or immobilized on polymeric supports [1]. For the biosorbents obtained by microorganism immobilization (which offers several advantages such as easy separation, enhanced operational stability, multiple uses, being incorporable into fixed and fluidized bed columns and higher productivity), different natural or synthetic polymers can be used for the production of inexpensive, non-toxic carriers with reactive functional groups [3,4]. From these, natural polymers include chitosan, alginate, agar, collagen and agarose, and synthetic polymers include poly-acrylamide, polyvinyl alcohol, polyethylene-glycol, polypropylene, polyethylene, polyvinylchloride, poly-urethane and polyacrylonitrile [3,4].…”