Application of Biosorption for Removal of Heavy Metals from Wastewater

Abstract

Fresh water accounts for 3% of water resources on the Earth. Human and industrial activities produce and discharge wastes containing heavy metals into the water resources making them unavailable and threatening human health and the ecosystem. Conventional methods for the removal of metal ions such as chemical precipitation and membrane filtration are extremely expensive when treating large amounts of water, inefficient at low concentrations of metal (incomplete metal removal) and generate large quantities of sludge and other toxic products that require careful disposal. Biosorption and bioaccumulation are ecofriendly alternatives. These alternative methods have advantages over conventional methods. Abundant natural materials like microbial biomass, agro-wastes, and industrial byproducts have been suggested as potential biosorbents for heavy metal removal due to the presence of metal-binding functional groups. Biosorption is influenced by various process parameters such as pH, temperature, initial concentration of the metal ions, biosorbent dose, and speed of agitation. Also, the biomass can be modified by physical and chemical treatment before use. The process can be made economical by regenerating and reusing the biosorbent after removing the heavy metals. Various bioreactors can be used in biosorption for the removal of metal ions from large volumes of water or effluents. The recent developments and the future scope for biosorption as a wastewater treatment option are discussed.

Removal of heavy metals from aqueous media by biosorption

“…In the metabolism dependent biosorption, precipitation occurs as a response by the microorganisms' active defence system in the presence in an environment containing toxic metal ions (Perpetuo et al, 2011). In the metabolism independent biosorption, precipitation occurs due to chemical reactions between the functional groups of the cell wall of the biosorbent and the metal ion, the reactions may involve oxidation-reduction reactions (Kanamarlapudi et al, 2018). A study confirmed the…”

“…Simple diffusion is also a basic mechanism observed in most types of biosorption (Sao, 2014). Several factors can contribute in controlling the mechanisms, those include the chemical, stereochemical and coordination characteristics of the metal of interest which involves the ion mass, ionic radius and the oxidation state of the metal ion (Kanamarlapudi, Chintalpudi, & Muddada, 2018). The properties of the biosorbent of choice also affect the mechanism of biosorption, properties such as the number of reactive binding sites, accessibility and availability of binding sites, type of binding site and the affinity between the binding site of the biosorbent and metal ion of interest (Abdi & Kazemi, 2015).…”

“…The properties of the biosorbent of choice also affect the mechanism of biosorption, properties such as the number of reactive binding sites, accessibility and availability of binding sites, type of binding site and the affinity between the binding site of the biosorbent and metal ion of interest (Abdi & Kazemi, 2015). There are other factors which are based on the environmental conditions that biosorption is taking place such as pH, temperature and complexity of solution containing the metal ion (Kanamarlapudi et al, 2018). In some cases, more than one mechanism may take place in a multi-step process mechanism, biosorption of uranium by Aloe vera waste involved physical adsorption, ion exchange, complexation and precipitation (Noli et al, 2019).…”

“…It has been reported that upon binding of heavy metal ions such as copper(II), cadmium(III) and zinc(II) to alginate of brown algae, an enhanced release of calcium, potassium, magnesium and sodium was observed due to ion exchange mechanism (Abdi & Kazemi, 2015) (Ahalya et al, 2003). A study reported that rice straws, as an example of non-metabolism dependent biosorbent, were able to biosorb cadmium(II) ions by ion exchange with sodium, potassium, magnesium and calcium (Kanamarlapudi et al, 2018). In addition, it was found that pH of solution can affect some biosorption mechanisms such as ion exchange.…”

“…The biosorption mechanism of lead ions by hami melon peels was achieved by ion exchange at low pH, while at higher pH it was achieved by electrostatic interactions between carboxylate and hydroxylate groups on the biomass and lead ions (Bashir et al, 2019). Spirulina, a cyanobacteria, was capable of biosorbing chromium(III), cadmium(II) and copper(II) through ion exchange by identified functional groups including carboxyl, phosphate and hydroxyl groups (Kanamarlapudi et al, 2018).…”