Biosorption

Biosorption is a physiochemical process that occurs naturally in certain biomass which allows it to passively concentrate and bind contaminants onto its cellular structure. Biosorption can be defined as the ability of biological materials to accumulate heavymetals from wastewater through metabolically mediated or physico-chemical pathways of uptake. Though using biomass in environmental cleanup has been in practice for a while, scientists and engineers are hoping this phenomenon will provide an economical alternative for removing toxic heavy metals from industrial wastewater and aid in environmental remediation. Biosorption is a physiochemical process that occurs naturally in certain biomass which allows it to passively concentrate and bind contaminants onto its cellular structure. Biosorption can be defined as the ability of biological materials to accumulate heavymetals from wastewater through metabolically mediated or physico-chemical pathways of uptake. Though using biomass in environmental cleanup has been in practice for a while, scientists and engineers are hoping this phenomenon will provide an economical alternative for removing toxic heavy metals from industrial wastewater and aid in environmental remediation. Pollution interacts naturally with biological systems. It is currently uncontrolled, seeping into any biological entity within the range of exposure. The most problematic contaminants include heavy metals, pesticides and other organic compounds which can be toxic to wildlife and humans in small concentration. There are existing methods for remediation, but they are expensive or ineffective. However, an extensive body of research has found that a wide variety of commonly discarded waste including eggshells, bones, peat, fungi, seaweed, yeast and carrot peels can efficiently remove toxic heavy metal ions from contaminated water. Ions from metals like mercury can react in the environment to form harmful compounds like methylmercury, a compound known to be toxic in humans. In addition, adsorbing biomass, or biosorbents, can also remove other harmful metals like: arsenic, lead, cadmium, cobalt, chromium and uranium. Biosorption may be used as an environmentally friendly filtering technique. Chitosan is among the biological adsorbents used for heavy metals removal without negative environmental impacts. The idea of using biomass as a tool in environmental cleanup has been around since the early 1900s when Arden and Lockett discovered certain types of living bacteria cultures were capable of recovering nitrogen and phosphorus from raw sewage when it was mixed in an aeration tank. This discovery became known as the activated sludge process which is structured around the concept of bioaccumulation and is still widely used in wastewater treatment plants today. It wasn't until the late 1970s when scientists noticed the sequestering characteristic in dead biomass which resulted in a shift in research from bioaccumulation to biosorption. Though bioaccumulation and biosorption are used synonymously, they are very different in how they sequester contaminants: Biosorption is a metabolically passive process, meaning it does not require energy, and the amount of contaminants a sorbent can remove is dependent on kinetic equilibrium and the composition of the sorbents cellular surface. Contaminants are adsorbed onto the cellular structure. Bioaccumulation is an active metabolic process driven by energy from a living organism and requires respiration. Both bioaccumulation and biosorption occur naturally in all living organisms however, in a controlled experiment conducted on living and dead strains of bacillus sphaericus it was found that the biosorption of chromium ions was 13–20% higher in dead cells than living cells. In terms of environmental remediation, biosorption is preferable to bioaccumulation because it occurs at a faster rate and can produce higher concentrations. Since metals are bound onto the cellular surface, biosorption is a reversible process whereas bioaccumulation is only partially reversible. Since biosorption is determined by equilibrium, it is largely influenced by pH, the concentration of biomass and the interaction between different metallic ions.