Immobilized microbial biosorbents for heavy metals removal

Abstract

Intensive industrial and urban growth has led to the release of increasing amounts of environmental pollutants. Contamination by metals, in particular, deserves special attention due to their toxicity and potential to bioaccumulate via the food chain. Conventional techniques for the removal of toxic metals, radionuclides and precious metals from wastewater all have a number of drawbacks, such as incomplete metal extraction, high cost and risk of generating hazardous by‐products. Biosorption is a cost‐effective and environment‐friendly technology, an alternative to conventional wastewater treatment methods. Biosorption is a metabolically independent process, in which dead microbial biomass is capable of removal and concentrating metal ions from aqueous solutions. Free microbial biosorbents are of small size and low density, insufficient mechanical stability and low elasticity, which causes problems with metal ion desorption, separation of the sorbent from the medium and its regeneration. Hence, the possibilities for the implementation of continuous biosorbent processes for metal removal in flow‐type reactor systems are reduced and the practical application of biosorption in industrial conditions is limited. By immobilizing microbial biomass on suitable carriers the disadvantages of free biosorbents are eliminated and more opportunities for practical use of biosorption become available. This review examines different immobilization techniques and carriers, certain basic features and possibilities of using immobilized microbial biosorbents for the removal and concentration of metals from aqueous solutions.

A Critical Review on the Ubiquitous Role of Filamentous Fungi in Pollution Mitigation

“…Following intracellular conversion, micropollutants can either be stored within the cell or secreted to the surrounding medium [29], where they can be further degraded by other microorganisms [27], similarly to natural nutrient cycles. Yet, cell wall accounts for a great fraction of the fungal biomass and its importance for sorption of micropollutants such as heavy metals is well documented in the literature [30]. It is important to mention, however, that extracellular and intracellular enzymes, cell wall, and surfactants can work in tandem for the removal or detoxification of micropollutants, where the type of micropollutants and fungal strain dictates their contribution level [16••, 31].…”

Biosorption of Congo Red and Methylene Blue by pretreated waste Streptomyces fradiae biomass - Equilibrium, kinetic and thermodynamic studies

“…This unnecessary biomass, after suitable pretreatment, has been used for biosorption of metals and dyes from aqueous solutions. [21][22][23][24] Congo Red (CR) is a benzidine-based anionic diazo dye that can cause allergic reactions and can be metabolized to benzidine -a carcinogenic product. 25 Methylene Blue (MB) is a tricyclic phenothiazine cationic dye used in different fields: textile, paper, rubber, plastics, leather, cosmetics, pharmaceutical and food industries.…”

Biorremediación de aguas con metales pesados mediante biomasa microalgal

“…Las microalgas se inmovilizan al ser mezcladas con la matriz previa a la conformación del polímero, quedando encapsuladas en la estructura tridimensional del polímero y permaneciendo en el interior debido a que los poros del polímero presentan un tamaño menor al de las células de las microalgas, por lo que el fluido fluye a través de este. Las matrices que más se han utilizado para el desarrollo de la inmovilización de la biomasa de microalgas son: Alginato de sodio Silva et al, 2012), polisulfona, poliacrilamida y poliuretano (Stoytcheva et al, 2018).…”

“…Para que un sistema de inmovilización de microalgas sea efectivo, este debe ser estable y no debe perjudicar en ningún modo la estabilidad estructural, fisiológica ni metabólica de las células. Cambios en la estructura de la pared celular pueden disminuir la capacidad de sorción de la biomasa inmovilizada (Stoytcheva et al, 2018). En cuanto a su cinética de crecimiento, se ha demostrado que las células que forman parte de un proceso de inmovilización presentan un periodo de latencia mayor en comparación con las células libres, con una diferencia de hasta dos días en el periodo de crecimiento exponencial, diferencia que se mantiene hasta una vez que se alcanza la fase estacionaria de crecimiento en el cultivo de las microalgas (Moreno-Garrido, 2008).…”

“…Para la aplicación industrial de la biosorción, parece ser indispensable preparar biosorbentes que mantengan la habilidad que posee la biomasa microalgal de adsorber los iones metálicos durante un proceso de tratamiento continuo . La mayoría de la investigación en esta área se ha ido enfocando en el uso de biosorbentes granulados operando en columnas, de una manera parecida a las resinas de intercambio iónico, aplicando técnicas de inmovilización y configuraciones de reactores en columnas de relleno, tradicionales en la ingeniería química (Stoytcheva et al, 2018).…”