MATERIALS AND METHODS

Materials: Materials used in the study carried out from June 2010 to March 2011 were e-waste items, analytical reagent chemicals and laboratory equipment. E-waste materials (containing lead) were collected from vendors of ICTs spare-parts and ICTs repairers in C-To-C Business Plaza, Nkpokiti Street, Enugu, Nigeria. All chemicals (analytical reagent grade) and laboratory wares and equipment were obtained from the laboratory of the Department of Medical Laboratory Sciences, Faculty of Health Sciences and Technology, College of Medicine, Enugu Campus, University of Nigeria, Nsukka.

Methods: E-waste processing usually first involves recovery of the items from consumers and services providers. The equipment are dismantled into various parts (metal frames, power supplies, circuit boards, plastics) often by hand. This enables recognition of working and repairable parts, including chips, transistors, RAM etc. The alternative process obtained in technologically advanced countries is the bulk system practice involving sophisticated machines (shredders, separators, screens and granulators). Metal and plastic fractions are obtained sold to smelters or plastic recyclers. Magnets, eddy currents and trammel screens are employed to separate glass, plastic and ferrous and non-ferrous metals, which can be further separated at a smelter. Leaded glass from CRTs is reused in car batteries, ammunition and lead wheel weights, or sold to foundries as a fluxing agent in processing raw lead ore. Copper, gold palladium, silver and tin are valuable metals sol to smelters for recycling. Hazardous smoke and gases are captured, contained and treated to mitigate environmental threat (Walraven, 2007).

Lead is applied in electrical and electronic devices as old solder, CRT monitor glass, lead-acid batteries and some formulations of PVCs. The e-waste items were first hand-dismantled into various parts (metal frames, power supplies, circuit boards, plastics). The parts containing old solder (lead) were mechanically separated and lead was mechanically extracted from them by use of soldering iron. The CRT monitor glass and lead-acid batteries were recycled intact (as practiced in developed countries).

Reactions and characterization of lead-extract from e-wastes and its product: Common chemical reactions and physical properties of lead were used to characterise the lead-extract from the e-waste materials and its products. To this end, 800 mL of dilute trioxonitrate(V) acid was added to 100 g of the lead-extract from e-waste in 2 L glass beaker. The reactants were heated until insoluble solid stopped forming. The solid product was obtained by filtration and dried overnight in Gallenkamp oven at 120°C. The product was inspected for colour to see if it tallied with lead (II) oxide colour in the literature.

The solubility of the product in water was tested by mixing 223 g of the solid product with 250 mL distilled deionized water in 1 L conical flask which was then shaken in an electric shaker for 2 h. The solid was filtered out, dried in Gallenkamp oven at 120°C and reweighed to ascertain its solubility or otherwise in water (Ogbuanu, 2005).

The melting point apparatus was used to determine the melting point of the solid obtained in order to compare it with the literature value.

Consideration of suitable reactor material for recycling of lead from e-wastes: In consideration of cost-effectiveness, availability and inertness with reactants and stability in the conditions of the reactions, metallic materials commonly used for fabrication of chemical reactors are metals: copper, iron, zinc and alloys (Ohia et al., 2005). Other materials used for construction of chemical reactors are glass and plastic materials (Shreve and Brink, 1977). These materials were considered for suitability for the chemical reactor for recycling of lead-extract from e-waste materials which involved lead and dilute trioxonitrate (V) acid, as reactants and lead (II) trioxonitrate (V), nitrogen (II) oxide, lead (II) oxide, nitrogen (IV) oxide and oxygen as products.

RESULTS AND DISCUSSION

Production and caharacterisation of lead(II) oxide from e-wastes: Treatment of lead extract with dilute trioxonitrate (V) acid led to the release of gas and the formation of an insoluble solid which decripitated and decomposed on heating. The gas was suspected to be nitrogen (II) oxide, NO, while the resulting solid product was light yellow, insoluble in water and melted at 886.01°C.

This was in agreement with the report of Ababio (2005) that lead reacts with dilute trioxonitrate (V) acid to yield lead (II) trioxonitrate (V) and nitrogen (II) oxide, as shown in the chemical equation below.

The nitrogen (II) oxide, NO, went off as gas in the open reactor, while the lead (II) trioxonitrate (V) decripitated and decomposed on heating to lead (II) oxide, nitrogen (IV) oxide and oxygen.

Again, both nitrogen (IV) oxide and oxygen went off as gases, leaving lead (II) oxide as solid product. Daintith, (2000) reports that lead (II) oxide is light yellow insoluble in water and melts at 886°C. The solid product was therefore, confirmed to be lead (II) oxide.

Recycling of lead (II) oxide: Lead (II) oxide is required in the industry for making lead accumulators and lead glass and as drier in paints, varnishes and glazes, among others (Ababio, 2005; Daintith, 2000; Kneen et al., 1972). Recycling the lead(II) oxide product obtained from the lead-extract from e-wase materials to the industry will reduce the environmental pollution from toxic lead contained in significant quantity in e-waste materials.

The recycling is necessary because according to Woolf et al. (2007) lead is a very strong poison. When lead dust is inhaled some of the poison can stay in the body and cause serious health problems. Worse still it is more common for lead poisoning to build up slowly over time from repeated exposure to small amounts of lead in which case, there will be no obvious symptoms. Again, low levels of lead exposure can harm a child’s mental development. Over 10 mg per deciliter is a definite concern.

Exposure to lead through occupational means or hobbies constiues the highest risk of predisposing individuals to lead poisoning. In adults, lead can increase blood pressure and can cause digestive problems kidney damage, nerve disorders, sleep problems, muscle and joint pain and mood changes. Foetuses and children up to six years of age are considered the at-risk age group for lead poisoning because young children, infants and foetuses absorb lead more readily than adults. And a small amount of lead that may have little effect on an adult can have disastrous consequences on a child. The presence of lead dust can cause difficulties during pregnancy because lead enters the bloodstream and can pass the placental barrier from the mother to the unborn child, thereby poisoning the foetus before birth.

Classification of the consequences of lead poisoning by toxicity levels has shown decreased learning decreased verbal abilit, early signs of Attention-Deficit Hyperactivity Disorder (ADHD) and low Intelligence Quotient (IQ) as general effects. Mild toxicity produces abdominal discomfort, lethargy, mild fatigue, myalgia and paresthesia. Moderate toxicity produces constipation, irritability, difficulty concentrating, diffuse abdominal pain, mild fatigue, headache, muscular exhaustibility, tremor, vomiting and weight loss. Severe toxicity produces colic, encephalopathy (seizures, coma, death) lead line on gingival tissue and paresis or paralysis.

Karri et al. (2008), Timbrell (2008), Pearce (2007), Marshall and Bangert (2008), Patrick (2006), Needleman (2004) and James et al. (2006) report that the symptoms and signs of lead poisoning vary according to the individual and the duration of lead exposure. They may be subtle and someone with elevated lead levels may have no symptoms. Symptoms usually develop over weeks to months as lead builds up in the body during a chronic exposure, but acute symptoms from brief intense exposures also occur. Symptoms from exposure to organic lead occur rapidly probably because organic lead is soluble in lipid and is. therefore, more toxic than inorganic lead. Poisoning by organic lead compounds has symptoms predominantly in the central nervous system such as insomnia, delirium, cognitive deficits, tremor, hallucinations and convulsions.

The main symptoms in adults are headache, abdominal pain, memory loss, kidney failure, male reproductive problems and weakness, pain, or tingling in the extremities. The classic signs and symptoms in children are loss of appetite, abdominal pain, vomiting, weight loss, constipation, anaemia, kidney failure, irritability, lethargy, learning disabilities and behavior problems. Children may also experience hearing loss, delayed growth, drowsiness, clumsiness, or loss of new abilities especially speech skills. Symptoms may appear in children at lower blood lead levels than in adults.

In acute poisoning, typical neurological signs are pain, muscle weakness, paraesthesia and rarely symptoms associated with encephalitis. Abdominal pain, nausea, vomiting, diarrhoea and constipation are other symptoms of acute lead poisoning. Lead's effects on the mouth include astringency and a metallic taste. Gastrointestinal problems, such as constipation, diarrhoea, poor appetite, or weight loss are common in acute poisoning. Absorption of large amounts of lead over a short time can cause shock (insufficient fluid in the circulatory system) due to loss of water from the gastrointestinal tract. Haemolysis (the rupture of red blood cells) due to acute poisoning can cause anaemia and haemoglobin in the urine. Damage to kidneys can cause changes in urination such as decreased urine output. People who survive acute poisoning often go on to display symptoms of chronic poisoning.

Chronic poisoning usually presents with symptoms affecting multiple systems but is associated with three main types of symptoms: gastrointestinal, neuromuscular and neurological. Central nervous system and neuromuscular symptoms usually result from intense exposure while gastrointestinal symptoms usually result from exposure over longer periods. Signs of chronic exposure include loss of short-term memory or concentration, depression, nausea, abdominal pain, loss of coordination and numbness and tingling in the extremities. Fatigue, problems with sleep, headaches, stupor, slurred speech and anemia are also found in chronic lead poisoning. A "lead hue" of the skin with pallor is another feature. A blue line along the gum, with bluish black edging to the teeth is another indication of chronic lead poisoning. Children with chronic poisoning may refuse to play or may have hyperkinetic or aggressive behaviour disorders.

Suitable reactor material for recycling of lead from e-wastes: According to Ohia et al. (2005) copper reacts with trioxonitrate (V) acid to form nitrates. But lead also reacts with trioxonitrate (V) acid to form lead (II) trioxonitrate (V) (Ababio, 2005). Therefore, copper is unsuitable for the reactor as it interferes in the lead-acid reaction.

Pig or cast iron contains impurities - sulphur, silicon, phosphorus and about 5% carbon. Wrought iron contains 0.1% carbon while ordinary steel (iron) contains 0.1-1.5% carbon. Iron reacts with dilute trioxonitrate (V) acid (HNO_3(aq)) to give a mixture of products, including ferric nitrate or iron(II) trioxonitrate (V) Fe(NO₃)₂ and ammonium nitrate or ammonium trioxonitrate(V) NH₄NO₃. The reactions with inorganic acids render iron unsuitable for the chemical reactor because of interference in the lead-acid reaction. Besides, iron rusts, because of the presence of impurities, water and oxygen in it (Ohia et al., 2005). Zinc belongs to the first group of transition metals with copper and iron. Therefore, zinc is similar in chemical reactions to copper and iron (Ohia et al., 2005). Therefore, like copper and iron zinc was considered unsuitable for the chemical reactor for lead recycling.

Alloys are mixtures of two or more metals. Brass alloy contains copper and zinc, stainless steel alloy is a mixture of iron and chromium and nickel, bronze alloy is a mixture of copper and aluminum and tin and magnesium, soft solder alloy contains lead and tin etc. Alloys were therefore, considered unsuitable for the reactor for lead recycling from e-wastes because of the interfering reactions of their components with the reactants (Ohia et al., 2005).

Since, glass has no interfering reactions it was suitable. But it is risky to use glass on account of imminent frequent breakage and replacement with attendant losses of material time and other resources.

Fig. 1:	Flowchart for the extraction and recycling of lead from e-wastes

On the other hand, plastic (PVC) materials were found to be suitable for the recycling process of lead from e-waste items because it has no interfering reactions, is available and durable without the risk of breakage. This compares with earlier reports (Ababio, 2005; Daintith, 2000; Kneen et al., 1972; Shreve and Brink, 1977).

Flowchart for the extraction and recycling of lead from e-wastes: The flowchart for the extraction and recycling of lead from e-wastes is given in Fig. 1.

CONCLUSION AND RECOMMENDATIONS

There are unavoidable reasons for the rapid increase in the generation of e-wastes in developing countries. These e-wastes contain lead-a hazardous chemical element-in significant quantity. The emission of lead from these wastes improperly discarded in the environment lead to health hazards, as people inhale the polluted air. Therefore, it has become necessary to manage e-wastes prudently and to make policies to that effect, in order to minimize the environmental and health hazards arising from emissions of lead from e-waste materials.

The study has shown that lead can be extracted from e-waste materials and converted to lead (II) oxide demanded in the industry for making lead accumulators and lead glass and as drier in paints, varnishes and glazes. And, that plastic (PVC) reactors would be best suited for the chemical raection process. It is, therefore, recomended that: