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This study assessed the progression of Pb, Cd and Cr concentrations in plastic components (PCs) and printed wiring boards (PWBs) of 59 end-of-life (EoL) mobile phones (MPs) produced between 2000 and 2015 by two leading original equipment manufacturers (OEMs) patronized by Nigerians. This was done to study the behavior of OEMs in complying with some widely acceptable regulations. Metals in PCs and PWBs of MPs were extracted following EPA 3050B method and extracts were analyzed using atomic absorption spectrophotometry technique. Furthermore, Toxicity Characteristic Leaching Procedure (TCLP) test was conducted on selected samples to assess metal leachability in landfill conditions. Summary of results (mg/kg) for PCs and PWBs for MPs produced by OEM 1 and OEM 2 in brackets ranged thus: PCs, Pb: 5.00 -195 (LOD-1750), Cr: LOD-6050 (LOD-2170) and Cd: LOD-1.00 (LOD-5.75) while PWBs, Pb:129-9750 (5.00-12125), Cr: LOD-5488 (LOD-4000) and Cd: LOD-1.00 (0.25-1.00). There were no regular trends for all metals for both OEMs. Results suggest that a greater percentage of MPs produced till 2015 contained Pb and Cr higher than RoHS and TTLC limits. Furthermore, 50% of TCLP extracts contain Pb higher than EPA limit of 5 mg/L. Therefore, EoL MPs arising in Nigeria should be handled as hazardous materials. [ABSTRACT FROM AUTHOR]

In this study, soil contamination by toxic metals released from cathode ray tubes (CRTs) openly discarded within the vicinities of artisans' workshops in Nigeria was assessed in order to ascertain the metal leaching potential of CRTs, mobility and bioavailability of the leached metals in soil. Furthermore, the ecological geochemistry of the impacted soils was carried out. Seventy soil samples were randomly collected from thirty five locations at depths 0 - 15 cm (topsoil) and 15 - 30 cm (sub-soil), respectively from two selected states each within five geographical regions of Nigeria. Environmentally available lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni) and copper (Cu) were extracted from dried and sieved soil samples using aqua regia solution and were analyzed using flame atomic absorption spectrometry (AAS). Additionally, the metals were also sequentially extracted into five fractions and their concentrations determined using AAS. Concentration of Pb ranged from 0.4 - 6510 mg/kg with all top-soils exceeding the Nigerian NESREA regulatory limit of 164 mg/kg while Cd, Cr, Ni and Cu levels were within their respective regulatory limits. Geoaccumulation index values indicated that approximately 83% of all top-soils represented strong to extreme contamination by Pb while sequential extraction showed that majority of the extracted Pb was in the Fe-Mn oxide, residual and exchangeable forms. The results generally suggest that CRT disposal areas are highly polluted with Pb with significant amounts in bioavailable phases. Thus, waste CRTs are required to be managed in an environmentally sound manner to forestall any probable harm to ecological functioning of such areas. [ABSTRACT FROM AUTHOR]

Rapid increase in the use of flat screen image display devices in recent times has led to the replacement of cathode ray tube (CRT) image display devices. The environmental problems arising from CRT disposal is primarily due to the glass' high lead content. With landfilling being non-environmentally friendly, there is need to develop sustainable management methods. This study therefore investigated the incorporation of finely ground (< 0.6 mm) mixture of panel, funnel and neck CRT glass in concrete at 0%, 10%, 15%, 20% and 25% wt/wt replacement for sand, from where an optimum composition was obtained. The workability, compressive strength, elemental composition and lead leaching behaviour of concrete specimens were studied. The test results indicated that the workability of fresh concrete was negatively affected with increasing glass content. The compressive strength at 20% replacement level (29.4 MPa) was higher than the reference (20.3 MPa) by 44.8% after curing for 90 days. It was observed that lead concentration increased with increasing glass content but calcium decreased proportionally while lead leachability was within regulatory limits. This investigation thus revealed that finely ground CRT glass at 20% wt/wt replacement possesses the potential to be used in concrete as a partial replacement for fine aggregate. [ABSTRACT FROM AUTHOR]

Management of waste electrical and electronic equipment (WEEE) has recently attracted worldwide attention because of high metal concentrations in them. Evolution of toxic and precious metals utilized in WEEE can not only reflect the adventure of eco-design, but can also guide the final recycling option. Pb, As, Cu, Au, Sn and Ag were determined in 10 composite samples of printed circuit boards of cathode ray tube televisions (TV–PCBs) that were produced between 1980 and 2005. The obtained results indicated that average metal concentrations in all TV–PCBs were – Cu: 10.6 ± 4.1%, Sn: 4.21 ± 0.90%, Pb: 3.15 ± 0.54%, Ag: 0.0215 ± 0.0068%, Au: 0.0068 ± 0.0049% and As: 0.0007 ± 0.0004%. No remarkable difference was found in compositions of Pb and Sn over the years, suggesting that there were no major modifications of Sn/Pb solder used in joining the circuitry system. The average composition of Cu fluctuated between 5.10% in 1980 and 12.8% in the mid-1990s and decreased afterwards. The decreases in Ag and Cu compositions could possibly be associated with thinner layers of these metals in newer model products. [ABSTRACT FROM PUBLISHER]

Levels of Pb, Ni, Cr, Cu, Zn, and Cd in the glass screens (GS) and printed wiring boards (PWBs) of obsolete computer monitors (OCMs) were determined by flame atomic absorption spectrophotometry (FAAS) following standard digestion. Metal concentrations (mg kg−1) in GS were in the following ranges (medians in brackets): Pb ND – 3100 (46), Cd 0.5–2.6 (0.8), Cr ND – 18.7 (3.1), and Zn 8.1–600 (37) and in PWBs (mg kg−1): Pb 34,600 ± 17,000, Cd 11 ± 9, Cr 59 ± 45, Zn 15,900 ± 7800, Cu79,000 ± 22,600, and Ni 3200 ± 2500. In GS, the levels of the six metals were lower than their total threshold limit concentrations (TTLC), except for Pb with a TTLC of 1000 mg kg−1in 10% of the samples. In the PWBs, the TTLC of Pb and Cu (2500 mg kg−1) was exceeded many fold. For Zn (5000 mg kg−1) and Ni (2000 mg kg−1); they were exceeded by 90% and 65%, respectively. For OCMs manufactured in 2001 and later, Pb and Zn levels in GS and Cr, Zn, and Ni in PWBs were significantly reduced. [ABSTRACT FROM PUBLISHER]

This study investigated the potential of recycling defatted Carica papaya seeds biosorbent (DPS) waste with adsorbed Pb and Cd in clay bricks. Physico-chemical, microscopic and technological properties were performed on raw materials and fired probes incorporated with 0 wt.% to 15 wt.% DPS made by dry compression technique, dried and fired at 700°C, 800°C and 900°C. Leaching tests were conducted on fired probes to ascertain their environmental safety. Incorporation of DPS had remarkable influence on properties of fired materials. Water absorption and total linear shrinkage increased with increase in DPS content while compressive strength decreased. The properties of fired probes with ≤ 6 wt.% DPS achieved ASTM minimum requirement for Class 1 building bricks. Leaching tests on 6 wt.% DPS complied with EPA limits for Pb. [ABSTRACT FROM AUTHOR]

The potentials of tropical weeds namely, Nephrolepis biserrata, Panicum maximum, Eleusine indica, and Chromolaena odorata to accumulate lead (Pb) and cadmium (Cd) from soil within the premises of an automobile battery manufacturing company in Ota, south-western Nigeria, were explored. The weed samples were collected in both wet and dry seasons. Standard analytical methods were employed to collect, digest, and analyze the weeds. Lead levels in the weeds for both seasons ranged from 1990-4870, 1090-1730, 4800-7890, and 400-1210 µg g-1 dry weight (DW) for Nephrolepis biserata, Panicum maximum, Eleusine indica, and Chromolaena odorata, respectively, while the cadmium level in the weeds for both seasons ranged from 3.92-6.78 µg g-1 DW for N. biserata, 1.99-6.85 µg g-1 DW for P. maximum, 2.90-7.40 µg g-1 DW for E. indica, and 2.90-5.09 µg g-1 DW for C. odorata. There was no significant difference in the accumulation of both Pb and Cd for the two seasons. All the weeds showed Pb levels higher than the phytotoxic range. On the contrary, 99% of the weeds showed Cd concentration within the phytotoxic range. The weeds demonstrate good phytoremediation potentials of contaminated soil. [ABSTRACT FROM AUTHOR]