Biosorption of copper, cobalt and nickel (II) by marine brown algae Sargassum sp. in packed column

Heavy metal pollution represents an important environmental problem due to its toxic effects and accumulation throughout the food chain and hence in the human body. Biosorption is a potential alternative to traditional processes of metal ions removal. Biosorption utilizes the ability of biological materials to accumulate heavy metals from waste streams by either metabolically mediated or purely physico-chemical pathways of uptake. Biosorption has been studied in various types of biomass including marine algae, bacteria and fungi. Marine algae, a renewable natural biomass have attracted the attention of many investigators as organisms to be tested and used as new supports to concentrate and adsorb metal ions [1]. Modelling of biosorption isotherm data is important for predicting and comparing biosorption performance. Two, three and even four-parameter isotherm models are available for modelling adsorption data [2]. The objective of the present work was to asses the potential of Sargassum sp. for the biosorption of copper, cobalt and nickel. The experiments were conducted to study the effect of important design parameters such as pH, retention time, initial concentration and mass of biosorbent. At pH:4 the maximum uptake of Cu²⁺ and at pH:7 the maximum uptake of Co²⁺ and Ni²⁺ were obtained. Kinetic studies showed that about 80–90% of the total metal ions biosorption occur within 40min. The results showed that biosorption stages follow from second – order kinetic model. By increasing the initial concentration, uptake increased. The 3.5g of biosorbent shown higher uptake. Due to its outstanding copper, cobalt and nickel uptake capacity Sargassum sp. proved to be an excellent biomaterial for accumulating and recovering these ions from industrial solutions. Equilibrium data follow from Langmuir and Freundlich isotherms well. The high correlation coefficient showed the suitabvility of this method.

Table 1. First-order and second -order kinetic models constants

kinetic models		Cu	Ni	Co
		-0.022	-0.036	-0.013
First-order	K1 (min)-1	-0.008	-0.013	-0.008
		-0.013	-0.017	-0.005
	R2	1	1	1
		0.001	0.001	0.001
second -order	K2 (g/mg.min)	0.003	0.005	0.002
		0.002	0.004	0.004
	R2	1	1	1

Table 2. Isotherm constants of two-parameter models

Two-parameter models		Cu	Ni	Co
	qmax (mg/g)	0.50	5.00	3.12
Langmuir	b (L/mg)	0.15	0.01	0.03
	R2	0.84	0.97	0.98
	Kf (L/g)	0.001	0.04	0.14
Freundlich	n	0.34	1.03	1.45
	R2	0.90	0.94	0.94

Acknowledgement: The authors wish to thank Ms. Masomi from Department of Chemistry, North Tehran Branch, Azad Islamic University for Atomic absorption spectroscopy analysis, and Dr.Moazami for making available the sample of biomass.

References: [1] El-sikaily A., et al. (2007) Hazardous materials; [2] Vijayaraghavan K., et al. (2006) Hazardous materials, 304–308.