BIOACCUMULATION AND BIOSORPTION STUDY OF HEAVY METALS REMOVAL BY CYANOBACTERIA NOSTOC SP.

Abstract

Nowadays, various industrial and urban activities result in discharging enormous quantities of various pollutants and their accumulation in the environment. Considering that heavy metals in wastewater are a serious threat to the environment and human health and that conventional methods for their removal are not highly efficient, the current study mainly focuses on estimating cyanobacterial capability to accumulate different heavy metals from water and comparing bioaccumulation and biosorption processes. Cyanobacteria Nostoc sp. was used, and five heavy metals were selected for this experiment (Cd2+, Cu2+, Pb2+, Ni2+, Zn2+). Examined concentrations of HMs were 20 mg/dm3, 80 mg/dm3, and 200 mg/dm3 for the bioaccumulation study, while 20 mg/dm3 and 80 mg/dm3 of each HMs were used for biosorption experiments. Living cells of Nostoc sp. have the highest affinity for Pb2+ (98.15%) and Cu2+ (95.14%) removal from the solution by bioaccumulation. During the biosorption process, dried biomass of Nostoc sp., besides Pb2+ (92.27%) and Cu2+ (96.00%), shows a high affinity for Cd2+ (91.00%) removal. Living cyanobacterial cells of Nostoc sp. could accumulate 82% of Zn, while dried biomass adsorbs 87% of Zn2+. Although the highest bioaccumulation of Ni2+ was only 38% while using the biosorption process, it was significantly higher (63.80%). These results could provide a preliminary study for further investigation in the direction of the development of immobilized biosorbents which could be used for industrial effluent treatment.