hazardous metal
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Abstract Inappropriate e-waste processing in the informal sector is a serious issue in developing countries. Field investigations in microscale informal recycling sites have been performed to study the impact of hazardous metal(loid)s (released from e-waste dismantling) on the environment (water and soil). Eight hazardous metal(loid)s (Pb, Cd, Cu, Zn, As, Hg, Ni and Cr) were found at elevated levels in the monitored water and soil samples (Sangrampur, West Bengal) as a consequence of widespread informal e-waste handling and primitive processing. Pd, Cu and As were found in high concentrations in water samples (1.62, 1.40, 0.03 mgL-1 respectively). Significant levels of Cu, Pd and Cd were detected in collected soil samples, both topsoil (Cu up to 2328.60 ± 217.60, Pb up to 342.90 ± 32.36 and Cd 18.34 ± 3.81 mgkg-1) and subsurface soil (2491.40 ± 276.20, 1853.33 ± 144.79, 25.90 ± 9.53 mgkg-1), compared to the levels of Zn, As, Hg, Ni and Cr. The results of seasonal variation indicated that higher levels of these hazardous meta(loids) were detected in the pre-monsoon (Nov – May) season than the rest of the year, as open dumping/burning of e-waste were practiced commonly and frequently in the monitored sites. The results highlighted that the composition and the handling of e-waste were important factors affecting the metal(loid) concentrations. E-waste policy and legislation have great influence on the handling and disposal procedures. A novel improved e-waste management practice has been proposed to encourage eco-friendly and safe e-waste disposal. It is recommended that regulatory agencies and manufacturers should create a road map to convince the informal sector to develop a systematic approach towards a more standardized formal e-waste management practices at the microscale field level.

Wide ranges of low cost adsorbents were used to remove hazardous metal in aqueous solution and wastewater. The low cost adsorbents were usually collected from agricultural waste, seafood waste, food waste, industrial by-product and soil. These adsorbents are readily available in a copious amount. Some of the natural adsorbents appeared as good heavy metal removal, while some were not and require further modifications and improvements to enhance the adsorption capacity. Currently, heavy metals exist in most of the industrial wastewaters and water supplies are among the most severe environmental contaminants. Numerous research works have been conducted in this field, this review includes few potential solution containing papers.

Carbon-based materials, including graphene (GR), carbon nanotubes (CNTs), activated carbon, and biochar, are the most common materials often applied to separate heavy metals from the water stream. A key feature of carbon adsorbent is the functional group of its adjustable surfaces. Both GR and CNTs exhibit the most favorable materials and may be the right choice in the future because of their excellent nature and unique structure. In order to commercialize the use of carbon absorbent in the removal of heavy metals, the mechanism of adsorption of carbon on heavy metals must be fully understood. In view of the good properties of carbon-based materials, a detailed study of their characteristics and synthesis, and modifications should be highlighted. Therefore, this article will discuss the properties, modifications, and use of carbon-based materials as adsorbents for various hazardous metal ions.

ABSTRACT: This work investigated the thermal treatment to separate and concentrate economically valuable materials from laminates of crystalline silicon photovoltaic modules (i.e., photovoltaic modules without the aluminum frame and the junction box). Chemical characterization of the metal content was performed by X-Ray Fluorescence (XRF). The polymers of the backsheet were also characterized by Fourier Transform Infrared Spectroscopy (FTIR). The influence of the atmosphere (oxidizing and inert) on the decomposition of the backsheet was investigated by Thermogravimetric Analysis (TGA). Moreover, non-comminuted samples were tested for 4 thermal time lengths (30, 60, 90, and 120 min) in the furnace under ambient air. The degradation of the polymers was measured and 3 material fractions were obtained: silicon with silver and residual polymers (SS), glass and copper ribbons. Furthermore, there was no statistical difference between the mass losses of the samples submitted for 90 (13.62 ± 0.02 wt.%) and 120 min at 500 °C (p-value = 0.062). In the SS fraction, silver was 20 times more concentrated than in the ground photovoltaic laminate and 30 times more concentrated than high silver concentration ores. The SS fraction (about 6 wt.%) also presented low copper concentration and a high concentration of lead (hazardous metal). About 79 wt.% glass was obtained, as well as 1% copper ribbons (55.69 ± 6.39% copper, 23.17 ± 7.51% lead, 16.06 ± 2.12% tin). The limitations of the treatment and its environmental impact are discussed, and suggestions for industrial-scale application are given.

In this present work, we have investigated the arsenic, fluoride and nitrate removal by the poly (ether-ether-sulfone) (PEES)/nano-silver hybrid membranes effectively prepared by the non solvent induced phase separation. The prepared membranes were characterized by thermal and mechanical properties to investigate the influence of nano-silver on the final properties of the membranes. Hence, our experimental study is based on arsenic (III) and arsenic (V) rejection studies attempted at different pH. The results of this study revealed the As (V) removal by NF with a high rejection of 99.98% compared to As (III). Fluoride and nitrate studies were carried out at neutral pH and it showed more than 80% rejection. Based on this investigation, it was concluded that the PEES/nano-silver membranes were effectively applicable to remove hazardous metal ions.

Abstract Development of nanofilters with the capability to remove toxic metal ions from effluent wastewater will be of immense help to the leather industry. In this study, fibrous nanofilter (FNF) was prepared using micro cellulosic fiber (MCF) and tea leaves microparticles (TLM) blended in poly (vinyl) alcohol (PVA). FNF was analysed for its efficacy to remove hazardous metals from tannery effluent wastewater. The FNF had promising traits of tensile strength (19.24+0.05 Mpa), elongation at break (22.31+0.12 %), flexibility (10.88+0.05 %), water absorption (37.86+0.14 %) and desorption (32.54+0.33 %). The metal adsorption studies clearly reflected the removal of toxic Cr (VI) ions from the effluent water by FNF. The study establishes an economically feasible and highly efficient way to remove hazardous metal ions from effluent wastewater.