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Non-living (dried) biomass of five common filamentous algae belonging to Chlorophyta and Cyanophyta (Cyanobacteria) were screened for their metal ion sorption and removal efficiency in a batch system. A considerably higher magnitude of sorption of Pb 2+ and Cu 2+ by all the tested algae suggests the prevalence of Pb 2+ -and Cu 2+ -binding ligands in them. The Langmuir isotherm could more appropriately describe metal sorption by the test algae than the Freundlich isotherm. A 1 g l -1 biomass concentration of Pithophora odeogonia and Spirogyra neglecta, respectively removed 97 and 89% Pb 2+ in 30 min from a solution containing 5 mg l -1 initial concentration of Pb 2+ . Metal ion removal by the test algae decreased with increase in metal concentration in the solution. S. neglecta could remove >70% Pb 2+ even from a solution containing 75 mg Pb 2+ l -1 . S. neglecta and P. oedogonia could remove more than 75% of Pb 2+ and Cu 2+ from a multimetal solution, and therefore have tremendous potential for removing Pb 2+ and Cu 2+ from wastewaters containing several metal ions simultaneously. Other test algae, namely, Hydrodictyon reticulatum, Cladophora calliceima and Aulosira fertilissima were relatively less efficient in removing metal ions from solution.

Wollastonite was used as an adsorbent for the removal of Fe(II) at different experimental conditions. The extent of removal is favourable at low concentration and low temperature. Maximum adsorption was noted at pH 4.0. The batch adsorption kinetics has been described by a first order rate expression, and the surface mass transfer coefficients and diffusion coefficients have been calculated at different temperatures. The intraparticle transport of Fe(II) within the pores of wollastonite is found to be the rate limiting step. The applicability of the Langmuir isotherm for the present system has been tested at different temperatures. Thermodynamic parameters indicate the exothermic nature of Fe(II) adsorption on wollastonite. The variation of adsorption with pH has been explained on the basis of interaction of iron species with negatively charged constituents of adsorbent.