Adsorption of heavy metals using marine algae

The discharge of heavy metals into aquatic ecosystem has become a matter of concern in South Africa over the last few decades. These pollutants are introduced into the aquatic systems significantly as a result of various industrial operations. Conventional methods for metal removal such as ion exchange, reverse osmosis, etc. have proven to be expensive. Due to the increasing awareness of ecological effects of heavy toxic metals, a research on new and cheap technologies involving the removal of heavy toxic metals from wastewater on the principle of adsorption was investigated in this study. The aim of the study was to investigate the adsorption characteristics of marine algae on copper solution as an alternate cheaper option with emphasis on its adsorption efficiency, stability and regeneration. In this study, the rate and extent for removal of copper is subjected to parameters such as pH, initial metal concentration, biosorbent size, contact time, temperature and the ability of the biomass to be regenerated in sorptiondesorption experiments. The metal adsorption was found to be rapid within 25 minutes. The maximum copper uptake of 30 mg of copper / g of biomass has been observed, in the following conditions: 100 mg / L, 0.1 g of biomass, pH 4 and at temperature of 25C. Metal biosorption behaviour of raw seaweed Sargassum in six consecutive sorption-desorption cycles were also investigated in a packed-bed column, during a continuous removal of copper from a 35 mg/l aqueous solution at pH 4. The sorption and desorption was carried out for an average of 85 and 15 hours, respectively, representing more than 40 days of continuous use of the biosorbent. The weight loss of biomass after this time was 13.5%. The column service time decreased from 25 hrs in the first cycle to 10 hrs for the last cycle. From this study, it was found that copper uptake is increasing with increase in pH, with optimum being pH 4. The biomass of the marine algae Sargassum species demonstrated a good capacity of copper biosorption, highlighting its potential for effluent treatment processes.