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The effectiveness of adsorption for nickel removal from wastewater had made it an ideal alternative to other expensive treatment options. This paper deals with an investigation on coir based adsorbent (Puresorbe) in the removal of nickel from the aqueous solutions. The adsorption of nickel was carried out by varying the parameters such as agitation time, metal concentration, adsorbent dose, temperature and pH. The experimental isotherm data were analyzed using the Langmuir and Freundlich isotherms. Adsorption followed a second order rate expression for the particle size 250-500 microm at pH 6. The monolayer adsorption capacity was 15.31 mg nickel per gram of puresorbe. Thermodynamic parameters show the endothermic nature of nickel adsorption. A desorption study carried out using distilled water adjusted to pH of 2-10, suggests that ion exchange might be the mode of adsorption.

ABSTRACT:The effectiveness of Pb(II) ion removal from wastewater by adsorption methods has made this an ideal alternative to other expensive treatment options. This paper describes an investigation using a coir-based adsorbent (Puresorbe) for the removal of Pb(II) ions from aqueous solution. The adsorption of Pb(II) ions was studied varying parameters such as the agitation time, the metal ion concentration, the adsorbent dose, the temperature and the pH of the aqueous solution. The experimental isotherm data were analyzed using the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Tempkin isotherms. For a particle size of 250-500 µm at pH 3.0, the adsorption process followed second-order kinetics. The monolayer adsorption capacity at 30°C was 55.81 mg Pb(II) ion/g Puresorbe. The thermodynamic parameters showed the endothermic nature of Pb(II) ion adsorption. Desorption studies carried out using distilled water adjusted to a pH value of 2.0-7.0 suggested that the adsorption mode could be ion exchange. As the adsorbent raw material is discarded as waste during coir processing, usage of this material is expected to be economically viable.

The effects of cadmium (CdCl2·7H2O) on cellulase, urease, amylase, invertase and phosphatase were assessed for a period of 45 days in the presence and absence of earthworms [Lampito mauritii (Kinberg)] in alfisol soil. The activities of all enzymes significantly increased with longer incubation times (45 days) under laboratory conditions in both control and Cd-amended soils (both with and without earthworm incubation). However, the activities of all enzymes decreased with increasing Cd concentrations under laboratory conditions, both in the presence and absence of earthworms. In the presence of earthworms, cellulase, urease, invertase and amylase activities increased. However, phosphatase activity was lower in most of the Cd-amended soils in the presence of earthworms compared to its activity levels in soils lacking earthworms. These results show that earthworms modulated the stress imposed by Cd by providing suitable substrates, which in turn acted as stimulants for extracellular enzyme secretion by microbes, and by removing Cd through its accumulation in the tissues of the earthworms.