Heavy Metal Cu, Ni and Zn: Toxicity, Health Hazards and Their Removal Techniques by Low Cost Adsorbents: a Short Overview

Electroplating and metalworking industries discharge large amounts of heavy metals, including copper (Cu), nickel (Ni) and zinc (Zn) ions, in their effluents have been recognized as a major problem to human health and aquatic life. Copper is highly toxic because it is non biodegradable and carcinogenic, Copper has been reported to cause neurotoxicity commonly known as “Wilson’s disease” due to deposition of copper in the lenticular nucleus of the brain and kidney failure, Nickel exposure vary from skin irritation to damage of the lungs, nervous system, and mucous membranes and Zinc toxicity from excessive ingestion is uncommon but causes gastrointestinal distress and diarrhea. The current regulation of waste water and drinking water standards are require contamination of heavy metal reduced up to few parts per million. Several processing techniques are available to reduce the concentrations of heavy metals in wastewater, including precipitation, flotation, ion exchange, solvent extraction, adsorption, cementation onto iron, membrane processing, and electrolytic methods. Adsorption onto activated carbon is a well-known method for removing toxic metal ions, but the high cost of activated carbon restricts its use in developing countries, so cheap and effective alternatives for the removal of heavy metals should reduce operating costs, reduce the prices of products, improve competitiveness, and benefit the environment. The adsorption abilities of a number of low-cost adsorbents (e.g., cheap zeolites, clay, coal fly ash, sewage sludge, agriculture waste, tea waste, rice husk, coconut husk, neem leaves and biomass) have been determined for the removal of heavy metals from water.