MINIMIZING ENVIRONMENTAL POLLUTION OF LEAD BY SOLVENTEXTRACTION RECYCLING OF LEAD FROM E-WASTES Eneh, O.C., * Agunwmba, J.C.1 and Afiukwa, J.N. 2 *

Author for Correspondence, Institute for Development Studies, Enugu Campus, University of Nigeria, Nsukka; E-mail: [email protected] Tel.: +234-803-338-7472 1 Department of Civil Engineering, University of Nigeria, Nsukka. 2 Department of Industrial Chemistry, Ebonyi State University, Abakaliki, Nigeria

ABSTRACT The determination to access the global market system dictates growing adoption of the information communications technology (ICT) in Africa, whereas high poverty levels underlies the demand for the second-hand, inferior, low-priced ICT products, which soon outlive their usefulness in developing countries. In the absence of or weak environmental regulatory infrastructure and compliance, consumers discard the e-wastes improperly on agricultural soils and on water-ways. Lead (Pb) contained in some of these e-waste materials can pollute water through leachhing from the soil. Lead in the soil can be absorbed by crops consumed by man, thereby poisoning humans. Again, lead in the soil can be absorbed by plants consumed by animals, which are in turn, consumed by man, poisoning humans in the long run. Thus, as a hazardous component of waste electrical and electronic equipment (WEEE) found mainly in the cathode ray tube of personal computers and as soldiers in other electronic appliances, lead is one of the major environmental health risks, creating a challenge for the already unwholesome public health in Nigeria. The soldier parts of WEEE were sorted, crushed mechanically with a grinder and pulverized. Solvent-extraction of lead from the powder was carried out in ammoniacyanide-sulphite mixture at pH 9.5. The extract mixture was treated with dipheyldithiocarbazone (dithizone) solution. The resulting lead-dithizone complex was dissolved in chloroform and the absorbance was measured at 510nm against a blank solution. The third extraction in a sequence gave zero absorbance, indicating complete removal of lead from the wastes. The extracted lead was purified by roasting in air and reduction with carbon and was characterized in terms of colour, as well as melting and boiling points. The purified lead-extract was dull grey in colour with m.p. of 327.7 oC and b.p. of 1,739.7 oC. To minimize environmental and health hazards arising from lead contained in e-wastes, it was recommended that solvent-extraction technique should be applied to remove and recycle lead from WEEE collected from homes, offices and waste dumpsites. Keywords: Lead pollution, E-wastes, Solvent extraction, Recycling, Green environment INTRODUCTION Diverse electrical and electronic equipment (EEE) constitute an indispensable factor in the development of contemporary society. Information communications technology (ICT), which utilizes EEE, is a critical force driving globalization and a key catalyst in the attainment of the Millenium Development Goals (MDGs). Global economies, marketing, international trade, productive activities, as well as growing power of transnational

corporations(TNCs) and international finacial institutions activities are enhanced by ICT. With the concept of globalisation powered by ICT, the world population is brought under one homogeinised market (Nkamnebe, 2010; Eneh, 2008; Onah, 2001; Khor, 2001; Quattara, 1997). The ICT is sustained by advancement in computers. Every country in the world strives to cope with the emerging technical and developmental challenges, thereby placing high demand for EEE. To meet up with the rising ICT global challenges, there are rapid innovations in the development of computer hardware, such that quality and standards are compromised in many cases, resulting in shortening the useful life of computers. Consequently, waste electrical and electronic equipment (WEEE) are inadvertently being rapidly generated, particularly in developing countries that patronise the second-hand and sub-standard goods because of poverty and ignorance (Afiukwa, 2010). WEEE generation in developing countries is growing at an alarming rate, with serious consequences on space in artisan shops, offices, markets and farmlands. This creates serious environmental and health challenges amidst weak legal framework for appropriate waste disposal and weak waste management capacity to ccontend with indiscriminate disposal practices by individuals, corporate bodies and some waste management agencies. The hazardous WEEE materials are usually dumped in open fields near residential homes, offices, markets and on farmlands, the best disposal practices being incineration, which potends serious environmental and health dangers, as the chemical toxin contained in WEEE are released into the air by incineration. Farmland and agricultural produce are also contaminated through the leaching of the chemical toxins present in the e-wastes (Forge, 2007). Water supply is mostly polluted, to the detriment of human lives that are invariably exposed to the toxins by ingestion, water consumption and inhalation. Computer hardwares contain large amounts of lead (Pb), cadmium (Cd), mercury (Hg) and chromium (Cr). An average personal computer contains 5-8 pounds of Pb in the cathode ray tube, while the keyboard typically contains several pounds of Cd, Hg and Cr (Eldon and Bradley, 2002). Pb is a typical base metal in solder, cathode ray tube (CRT), monitor glass in computers, lead-acid batteries and some formulations of polyvinylchlorides (PVCs) found in virtually all ICT products (Murali, 2009). Amidst the absence of or weak environmental regulatory infrastructure and compliance, African consumers with pronounced throw-away mentality, discard the ewastes improperly, along with their lead hazardous component, adding to the challenges posed by the already unwholesome public health. ICT wastes from households, offices and commercial activities largely consists of incineration residues or waste placed in landfill sites, from which are emitted toxic gases (Madu, 2014; Eneh and Agbazue, 2011). The concept of sustainable development, and in particular environmental sustainability, empasizes the 3Rs: reduction in the use of limited resources, re-use of resources, and recycling (Onyido, 2014). The philosophy of green chemistry or sustainable chemistry emphasizes minimization or reduction or elimination of negative environmental impacts of chemicals and promotion of their reuse or recycle (US EPA, 2010). To address this, an earlier study (Eneh and Agunwamba, 2011) identified the need to reclaim and recycle lead from e-wastes materials in Africa, and converted lead extracted from e-wastes to lead (II) oxide for recycling to education, manufacturing and other industries. The

extraction process adopted was mechanical, by use of soldering iron. This extraction technique left a singificant portion of lead unextracted. A subsequent study (Afiukwa, Agunwamba and Eneh, 2014) attempted to recover lead by inorganic acid-precipitation from e-waste materials for recycling to industries. The extraction technique could not prove satisfactory, but needed further improvement. The present study explores the solvent-extraction technique for a more efficient process of reclamation of lead from ewastes for recycling, in view of minimising the enironmental pollution and the attendant health hazard of Pb contained in WEEE. The study was carried out between December 2013 and August 2014. MATERIALS AND METHODS MATERIALS The e-waste soldered materials were sourced from computer vendors in C-To-C Business Plaza, Nkpokiti Street, Enugu, Nigeria. The mechanical crusher and pulverizer were sourced from industrial machine fabricators and industrial support services providers at the Eastern Nigeria Industrial Estate, 30 Zik Avenue, Uwani, Enugu, Nigeria. All the reagents were of analytical grade. They included conc. ammonia solution potassium cyanide (KCN), sodium sulphite (Na2SO3), (0.88% NH3), diphenyldithiocarbazone (dithizone, C6H5N=NCSNHNHC6H5), chloroform (CHCl3) and distilled deionised water. Instruments included separatory funnel, pH metre, filter paper, Perkin Elmer Analyst 400 Model Spectrophotometre, graduated flak, and Gallenkamp m.p and b.p apparatus. The reagents and laboratory wares and instruments were obtained from the Department of Industrial Chemistry, Ebonyi State University, Abakaliki, Nigeria or Project Development Institute (PRODA), Emene-Enugu, Enugu State, Nigeria or the Faculty of Health Sciences & Technology or the Chemical Pathology Laboratory of the Department of Biochemistry, College of Medicine, Enugu Campus, University of Nigeria, Nsukka. METHODS Solvent-extraction In solvent extraction or liquid-liquid extraction technique, a solution (usually aqueous) is brought into contact with a second solvent (usually organic and essentially immiscible with the first), to enable the transfer of one or more solutes from the first (solution) into the second (solvent). The inorganic ion associates with oppositely charged ions to form a neutral extractable species. Such ion-association complexes may form clusters with increasing concentration, which are larger than just simple pairs, particularly in organic solvents. Many complexes of metals in aqueous solution are coloured: when extracted with an organic solvent, the coloured extract may be used directly for the determination of the concentration of the metal by colorimetric or, preferably, spectrophotometric techniques, which are particularly applicable with many chelate complexes. Examples of chelating and extraction reagents are acetylacetone (pentane-2,4-dione), 8-hydroxyquinoline (oxine), dimethylglyoxime, diphenyldithiocarbazone (dithizone), and sodium diethyldithiocarbamate. Lead forms a dithizone complex, which is soluble in dilute

ammonia solution, chloroform, and carbon tetrachloride to yield green solutions with an absorption maximum at 510nm (Vogel, 2002). Procedure for solvent-extraction of lead from e-wastes The e-waste items were first hand-dismantled into various parts (metal frames, power supplies, circuit boards, and plastics). The CRT monitor glass and lead-acid batteries were recycled intact (as practiced in developed countries), while the parts containing old solder (lead) were mechanically separated and crushed with the help of a grinder and powdered with the help of a pulverizer. The resulting powder was treated to a procedure adapted from Vogel (2002), as outlined below: About 0.67kg of the powdered e-waste materials was soaked for 2 minutes in 1,000 cm3 of distilled deionised water in a graduated flask and filtered. A 10cm3 of the solution contained in 250-cm3 separatory funnel was mixed with 75cm3 of ammoniacyanide-sulphite mixture (prepared by diluting 35cm3 ammonia solution with sp. gr. 0.88 and 3cm3 of 10% potassium cyanide solution to 100cm3, and then dissolving 0.15g of sodium sulphite in the solution). The pH of the solution was adjusted to 9.5 (pH metre) by cautious addition of hydrochloric acid, before the addition of 7.5cm3 of 5x10-3% solution of dithizone in chloroform (1cm3 of this solution is equivalent to about 20 microgramme of lead) and 17.5cm3 of chloroform. It was shaken for 1 minute and the phases were allowed to separate. The absorbance was determined at 510nm in a 10-cm absorption cell against a blank solution. A further extraction of the same solution gave zero absorption when the extraction of lead was complete. Procedure for purification and characterisation of lead from lead-extract The lead-extract was roasted in air. Carbon was introduced. The product was examined for colour, and the melting point (m.p.) was tested with Gallenkamp m.p. apparatus, while the boiling point (b.p.) was tested with the Gallenkamp b.p. apparatus. RESULTS AND DISCUSSION Solvent extraction of lead from the solution of powdered e-waste materials was carried out in triplicate stages. The inorganic lead (Pb2+) was extracted in dithizone in chloroform. The inorganic ligand formed a complex with lead, thereby neutralising its charge for efficient extraction into an organic phase (CHCl3). Lead in the green extract obtained in the CHCl3 layer could be easily determined spectrophotometrically by measuring the absorption at 510nm. After the first two stages, the solution absorbed light at 510nm for each case, but after the third extraction, the solution no longer absorbed light at 510nm (zero absorption). Absorption of light after the first and second extractions confirmed the presence of lead in the solution, while the zero absorption after the third extraction showed that solventextraction of lead was completed during the second extraction (without any lead left to be extracted in the third extraction stage). Although the presence of lead in ICT products is already established in the literature, the present study establihed its presence in e-waste materials. Thus, solvent-extraction procedure described can be used to free WEEE of Pb.

The result of roasting the extracted lead was its convesion to lead(II) oxide, which was reduced with carbon to metallic lead. The roasted and reduced lead-extract was dull grey in colour with m.p. of 327.7oC and b.p. of 1,739.7oC. Ababio (2011) reported that when lead is roasted, it yields lead(II) oxide, which can be reduced with carbon to get metallic lead, as represented in the equations below: 2Pb + 3O2 = 2PbO 2PbO + C = Pb + CO2 Isaacs, Daintith and Martin (2003) described lead metal as a heavy dull grey soft ductile metallic element with m.p. of 327oC and b.p. of 1,740oC. The findings on colour, m.p. and b.p. agreed with these reports. The purified lead extract can be recycled in form of PbO or Pb (Afiukwa, Agunwamba and Eneh, 2014; Eneh and Agunwamba, 2011). Hand-to-mouth ingestion of earth materials or water or chewing of children plastic toys are the primary causes of lead poisoning in children, while exposure to lead toxicity in adults is mainly due to inhalation of fumes, dusts and ingestion of water. Hu, Shih, Rothenberg and Schwartz (2007) reported that 35-40% of inhaled lead is deposited in the lungs and about 95% of of that goes into the bloodstream. Once lead is absorbed into the bloodstream, it distributes throughout the body and affects every organ and tissue (MingHo, 2001; Guidotti and Ragain, 2007). The central nervous system (CNS) is the main target organ. Neonates are most vulnerable to lead toxicity due to their rapid growth and high metabolic rates (Ming-Ho, 2001). Slight breeze predisposes one to exposed lead dust. At toxic level, lead impairs haem-biosynthesis and accelerates red blood cells destruction (Anglin-Brown, Armour-Brown and Labor, 1995 ), which ultimately leads to anaemia with lots of complications. CONCLUSION 1. Metallic lead has been successfully removed from waste electrical and electronic equipment (WEEE) by solvent extraction technique. 2. E-waste re-use, recycling and refurbishing is a strong factor in sustainable national development that would help to reduce material input into production and minimise the quantity of toxic waste generation in Africa and the world at large. 3. Public health endangered by hazards associated with WEEE abounding in homes, offices, markets and open dumpsites in developing countries can be abated by enhanced solvent-extraction of the toxic lead from WEEE. 4. The outcome of this study can help to improve the living condition of the people through the demobilisation of mobile lead compounds from the environment. RECOMMENDATIONS The following recommendations are proferred: •

There is the need for a functional and comprehensive legal framework for electrical and electronic equipment procurement, management and disposal of associated ewastes.

• • • •

Regular public enlightenment on the dangers associated with e-wastes is also recommended. Citizens should be motivated and compeled through enforcement of relevant laws and policies to deposit WEEE from homes and offices in designated spots for collection and sorting. Control of lead input into products, such as ICT products, paints, cables, toys and plumbing materials and solder is needful. To contain the rapidly growing applications of leaded and related materials, recycling industries should be in place to handle e-wastes.

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