Phycoremediation of heavy metals, factors involved and mechanisms related to functional groups in the algae cell surface - a review

The exorbitant usage of heavy metal in industries leads to accumulation in the ecosystem and causes various disorders. Many physico-chemical methods have developed for the removal of heavy metals from industrial wastewaters as well as the polluted environments. However, these conventional technologies are providing expensive, generate toxic secondary sludge, and not complete abatement. An alternative, the biological methods especially using algae for the treatment of metal-contaminated environments provides a cost-effective, rapid, and eco-friendly approach. Using algae (macro or micro) for removing pollutants (phycoremediation) is a versatile approach since algae can adapt easily with any environmental conditions and recognized as a sustainable technology for removing noxious heavy metals. Algal biomass contains a polyanionic cell wall that can bind heavy metals through the principle of adsorption (passive) onto the cell surface and absorption (active) into the cell with metal-binding peptides or contained in the vacuole. Moreover, various factors (pH, temperature, metal concentration, contact time, agitation speed) affect the biosorption of heavy metal. Thus, this review article deals with the abatement of heavy metals using macro and microalgae, factors involved and mechanisms, and functional groups involved in the cell surface. Besides, suggested that the industrial-scale data's are required for the real application.