Vermicompost as natural adsorbent for removing metal ions from laboratory effluents

The use of vermicompost as an adsorbent to remove Cd(11), Cu(11), Pb(II) and Zn(II) ions from laboratory effluents is proposed. Parameters such as adsorption pH, vermicompost amount, flow rate and particle size range were studied. An optimum pH range (2.5-5.0) was found for metal removal. The flow rate affected only slightly the removal of Cd(11) ions (about 10%). A decrease of about 20 and 27% was observed for Zn(II) and Cu(11) ions, whereas there was no change for Pb(11) ions. Higher metal removal was observed using particle size less than or equal to 150 mum and 2.5 g of vermicompost. For single-component solutions (pH 3.5, flow rate 5 ml/min), the maximum adsorption capacity of the vermicompost for Cd(11), Cu(11), Pb(II) and Zn(11) ions were 33.01, 32.63, 92.94 and 28.43 mg/ g, respectively. These values were obtained by applying the linear Langmuir equation. High adsorption capacity of vermicompost was demonstrated and an alternative for effluent treatment offered, especially due to its ease acquisition and low price. (C) 2002 Elsevier Science Ltd. All rights reserved.