Abstract:
The electronic waste (e-waste) is generated by collection, transportation, dismantling, crushing, disposal and informal recycling of electrical and electronic devices. The legal and or illegal export of electronic devices from developed countries to developing countries including Pakistan, India and Sri Lanka has become a subject of growing environmental concern. The informal recycling and unsafe disposal of e-waste is causing health risks due to its effects on the environment. This is first ever study conducted in Pakistan to assess the heavy metals contamination of the soil/ash collected from e-waste recycling sites in Karachi, Rawalpindi and Kamoki area. Eight heavy metals namely Pb, Cd, Cr, Ni, Cu, Zn, Co and Mn were studied using USEPA approved method “Toxicity Characteristic Leaching Procedure (TCLP)”. The analysis performed on Atomic Absorption Spectrometer (AAS) showed that the concentration Cd, Cr, Ni and Cu were higher as compared to the permissible limits of EU, USEPA and Indian Standard. It may be noted that there is no standard in Pakistan for permissible limit of heavy metals in soil. The concentration was found significantly different at the selected sites, which is attributed to the complex type of waste and process adopted. The concentration of heavy metals found from different sites revealed that computer, circuit boards, monitors, home appliances and drill machines are being burned at Karachi, computer, circuit boards, monitors, mobile phones are being burned at Rawalpindi and computer, circuit boards and wires are being burned at Kamoki.
The removal of heavy metals was also studied by using locally available, low cost agriculture waste like rice husk and peanut hull. Batch sorption studies were conducted to find the effect of pH, contact time and dosage of adsorbent. The results revealed that rice husk gives optimum sorption results 80 % at pH 9 with 8 g /100 ml adsorbent dosage at 4 hours contact time, whereas the peanut hull gives better sorption results 91 % at pH 5 with 8 g / 100 ml adsorbent amount at 4 hours contact time respectively at constant temperature 25 oC ± 3 oC. These results showed that peanut hull act as better adsorbent than rice husk for the removal of heavy metals from e-waste leachate solution.
