Environmental Impact of Processing Electronic Waste – Key Issues and Challenges

Extensive utilization of electric and electronic equipment in a wide range of applications has resulted in the generation of huge volumes of electronic waste (e-waste) globally. Highly complex e-waste can contain metals, polymers and ceramics along with several hazardous and toxic constituents. There are presently no standard approaches for handling, dismantling, and the processing of e-waste to recover valuable resources. Inappropriate and unsafe practices produce additional hazardous compounds and highly toxic emissions as well. This chapter presents an overview of the environmental impact of processing e-waste with specific focus on toxic elements present initially in a variety of e-waste as well as hazardous compounds generated during e-waste processing. Hazardous constituents/ and contaminants were classified in three categories: primary contaminants, secondary contaminants, and tertiary contaminants. Primary contaminants represent hazardous substances present initially within various types of e-waste; these include heavy metals such as lead, mercury, nickel and cadmium, flame retardants presents in polymers etc. Secondary contaminants such as spent acids, volatile/toxic compounds, PAHs are the by-products or waste residues produced after inappropriate processing of e-waste and the tertiary contaminants include leftover reagents or compounds used during processing. A detailed report is presented on the environmental impact of processing e-waste and the detrimental impact on soil contamination, vegetation degradation, water and air quality along with implications for human health. Challenges and opportunities associated with appropriate e-waste management are also discussed

Cell-mediated immune status in patients with squamous cell carcinoma of the oral cavity

Sixteen untreated patients with squamous cell carcinoma of the oral cavity were tested for in vitro immune status in comparison with the normal healthy donors. The parameters investigated were total leukocyte and lymphocyte counts, percentages and absolute counts of T- and B-cells in circulation, subsets of T-cells identified by the Fc receptors, phytohemagglutinin (PHA), and mixed lymphocyte culture (MLC) responses, natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) activities, and circulating immune complexes (CICs). Eight of these patients were retested 3 to 6 months after surgery. The results showed that there was an increase in leukocyte and lymphocyte counts, an increase in the percentage and absolute number of B-lymphocytes, an increase in the percentage of T-gamma cells, suboptimal PHA and MLC responses, normal NK and ADCC activities, and increased levels of CICs in untreated oral cancer patients. In the postoperative stage, except for a reduction in leukocyte and lymphocyte counts, other abnormalities remained unchanged. The CICs in treated patients correlated with the tumor load in that in three patients showing recurrence, the CIC level remained elevated, whereas in patients without evidence of the disease the CIC level was either low or comparable to the upper normal limits

The Antimicrobial Peptide Histatin-5 Causes a Spatially Restricted Disruption on the Candida albicans Surface, Allowing Rapid Entry of the Peptide into the Cytoplasm

Antimicrobial peptides play an important role in host defense against microbial pathogens. Their high cationic charge and strong amphipathic structure allow them to bind to the anionic microbial cell membrane and disrupt the membrane bilayer by forming pores or channels. In contrast to the classical pore-forming peptides, studies on histatin-5 (Hst-5) have suggested that the peptide is transported into the cytoplasm of Candida albicans in a non-lytic manner, and cytoplasmic Hst-5 exerts its candicidal activities on various intracellular targets, consistent with its weak amphipathic structure. To understand how Hst-5 is internalized, we investigated the localization of FITC-conjugated Hst-5. We find that Hst-5 is internalized into the vacuole through receptor-mediated endocytosis at low extracellular Hst-5 concentrations, whereas under higher physiological concentrations, Hst-5 is translocated into the cytoplasm through a mechanism that requires a high cationic charge on Hst-5. At intermediate concentrations, two cell populations with distinct Hst-5 localizations were observed. By cell sorting, we show that cells with vacuolar localization of Hst-5 survived, while none of the cells with cytoplasmic Hst-5 formed colonies. Surprisingly, extracellular Hst-5, upon cell surface binding, induces a perturbation on the cell surface, as visualized by an immediate and rapid internalization of Hst-5 and propidium iodide or rhodamine B into the cytoplasm from the site using time-lapse microscopy, and a concurrent rapid expansion of the vacuole. Thus, the formation of a spatially restricted site in the plasma membrane causes the initial injury to C. albicans and offers a mechanism for its internalization into the cytoplasm. Our study suggests that, unlike classical channel-forming antimicrobial peptides, action of Hst-5 requires an energized membrane and causes localized disruptions on the plasma membrane of the yeast. This mechanism of cell membrane disruption may provide species-specific killing with minimal damage to microflora and the host and may be used by many other antimicrobial peptides

Transforming waste plastic into reductants for synthesis of ferrosilicon alloy

A novel process to transform waste plastic as a reducing agent and therefore as an alternative carbonaceous source in the production of silicon bearing alloys is investigated. Bakelite, a thermoset plastic that is difficult to recycle, is used in this study. Heat treatment of Bakelite was carried out at 1550 °C in argon atmosphere to investigate volatiles generation, presence of ash impurities, carbon structure, and properties as a result of transformations occurring during heat treatment. Simultaneous influence of these properties on ferrosilicon alloy synthesis is established. Initial volatiles generation from Bakelite accelerated the rate of silica reduction, particularly the formation of silicon carbide (SiC) through gas phase reduction reactions of silica. Calcium carbonate (CaCO3) impurity in Bakelite acts as a fluxing agent and facilitates the separation of metal alloy from slag. Bakelite derived carbon obtained during heat treatment showed enhanced crystallinity coupled with lower levels of porosity in structure with increasing time. Carbon obtained through transformation of Bakelite could serve as a reducing agent to produce ferrosilicon. This scientific study of using Bakelite as a reductant will create new opportunities to re-form waste plastics as raw materials in ferrosilicon alloy synthesis

Synthesis of silicon carbide nanoparticles by using electronic waste as a carbon source

Around the world the amount of electronic waste is growing exponentially and considered to be an important environmental and health issue. The environmental friendly and resource recovery methodology is critically required for existing scenario to recycle electronic waste. In this paper, a novel approach to synthesise silicon carbide (SiC) nanoparticles by using electronic waste compact discs (CDs) char as a carbon source is reported. The synthesis is based on carbothermal reduction at 1550 C using waste CD char as the carbon source and silicon dioxide as the silicon source. FTIR, Raman and XPS results confirm the formation of SiC particles and XRD signifies the major phases of 3C-SiC. The size of synthesised SiC particles was in the range of 40-90 nm and was mainly composed of sphere shaped nanoparticles. This innovative approach of using electronic waste CDs as the carbon source for synthesising SiC nanoparticles will reduce the volume of waste in landfills and also the dependency of industries on traditional raw materials. © 2014 Elsevier B.V

Lightweight expanded aggregates from the mixture of waste automotive plastics and clay

Significant amount of waste associated with end of life vehicles enter waste stream each year and are usually disposed of in landfill, creating an environmental burden. Recycling automotive waste is very tedious and difficult due to its heterogeneous composition and nature. It is critically required to develop a solution to recycle and reuse these potential resources. In this paper, a novel recycling approach is established to produce lightweight aggregate by incorporating automotive shredded residual (ASR) plastics into clay at 1200 °C. The physical properties of lightweight aggregate such as bulk density, porosity and water absorption have been investigated. ASR plastics as pore-forming or gas releasing agent increased the porosity of the clay mixture. Incorporation of 2 wt% of ASR plastics into clay composite lead to a benefit of approximately 30% bulk density decrease and 40% porosity increase compared to the reference clay material used in this study. The obtained superior lightweight and porous aggregate products by using ASR plastics can be used in thermal insulation materials and also as substrates in soilless cultivation. This innovative approach could also help reduce the volume of autoplastics in landfills and could be a potential replacement of conventional additives in manufacturing composite materials for building applications

Study of structural evolution of chars during rapid pyrolysis of waste CDs at different temperatures

In this paper, the work dealt with the characterisation of chars obtained by rapid pyrolysis of waste compact discs (CDs) at different temperatures and its application as reductant in ironmaking industries. The rapid pyrolysis was performed at atmospheric pressure and temperatures ranging from 550 to 1550 °C. The obtained chars were characterised by ultimate analysis, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photon spectroscopy (XPS), N2 isothermal adsorption method and scanning electron microscopy (SEM). The results indicated that char structure changed upon different pyrolysis temperature. The char yield decreased from 22% to 18% and gradual increase in carbon/oxygen ratio was observed with increase in pyrolysis temperature from 550 to 1550 °C. The porosity in chars increased progressively with pyrolysis temperature, and maximum development of pores appeared at 850 °C with surface area 334 m2/g. At higher pyrolysis temperature, the chars became more aromatic and ordered, and aliphatic structures decreased significantly. The loss of functional groups at higher temperature such as carbonyl, aliphatic CH was evident by FTIR, XPS and Raman results. The ordered char structure obtained at 1550 °C was used as reductant carbon for iron oxide reduction process, and 90% reduction was achieved. The waste CD char obtained during pyrolysis indicates as a valuable supplementary carbon source for ironmaking industries. © 2014 Elsevier Ltd. All rights reserved