Recycling polymeric waste from electronic and automotive sectors into value added products

The environmentally sustainable disposal and recycling of ever increasing volumes of electronic waste has become a global waste management issue. The addition of up to 25% polymeric waste PCBs (printed circuit boards) as fillers in polypropylene (PP) composites was partially successful: while the tensile modulus, flexural strength and flexural modulus of composites were enhanced, the tensile and impact strengths were found to decrease. As a lowering of impact strength can significantly limit the application of PP based composites, it is necessary to incorporate impact modifying polymers such as rubbery particles in the mix. We report on a novel investigation on the simultaneous utilization of electronic and automotive rubber waste as fillers in PP composites. These composites were prepared by using 25 wt.% polymeric PCB powder, up to 9% of ethylene propylene rubber (EPR), and PP: balance. The influence of EPR on the structural, thermal, mechanical and rheological properties of PP/PCB/ EPR composites was investigated. While the addition of EPR caused the nucleation of the β crystalline phase of PP, the onset temperature for thermal degradation was found to decrease by 8%. The tensile modulus and strength decreased by 16% and 19%, respectively; and the elongation at break increased by ~71%. The impact strength showed a maximum increase of ~18% at 7 wt.%–9 wt.% EPR content. Various rheological properties were found to be well within the range of processing limits. This novel eco-friendly approach could help utilize significant amounts of polymeric electronic and automotive waste for fabricating valuable polymer composites.

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Environment polluting conventional chemical control compared to an environmentally friendly IPM approach for control of diamondback moth, <Emphasis Type="Italic">Plutella xylostella</Emphasis> (L.), in China: a review

The diamondback moth, Plutella xylostella, is recognized as a widely distributed destructive insect pest of Brassica worldwide. The management of this pest is a serious issue, and an estimated annual cost of its management has reached approximately US$4 billion. Despite the fact that chemicals are a serious threat to the environment, lots of chemicals are applied for controlling various insect pests especially P. xylostella. An overreliance on chemical control has not only led to the evolution of resistance to insecticides and to a reduction of natural enemies but also has polluted various components of water, air, and soil ecosystem. In the present scenario, there is a need to implement an environmentally friendly integrated pest management (IPM) approach with new management tactics (microbial control, biological control, cultural control, mating disruption, insecticide rotation strategies, and plant resistance) for an alternative to chemical control. The IPM approach is not only economically beneficial but also reduces the environmental and health risks. The present review synthesizes published information on the insecticide resistance against P. xylostella and emphasizes on adopting an alternative environmentally friendly IPM approach for controlling P. xylostella in China.     

Application of chemical oxidation to remediate HCH-contaminated soil under batch and flow through conditions

This is the first study describing the chemical oxidation of hexachlorocyclohexanes (HCHs) in contaminated soil under water saturated and unsaturated flow through conditions. Soil contaminated with β-HCH (45 mg kg^?1) and γ-HCH (lindane, 25 mg kg^?1) was sampled from former lindane waste storage site. Efficiency of following treatments was tested at circumneutral pH: H₂O₂ alone, H₂O₂/Fe^II, Na₂S₂O₈ alone, Na₂S₂O₈/Fe^II, and KMnO₄. Experimental conditions (oxidant dose, liquid/solid ratio, and soil granulometry) were first optimized in batch experiments. Obtained results revealed that increasing dose of H₂O₂ improved the oxidation efficiency while in Na₂S₂O₈ system, maximum HCHs were removed at 300 mM. However, oxidation efficiency was slightly improved by Fe^II-activation. Increasing the solid/liquid ratio decreased HCH removal in soil samples crushed to 500 μm while an opposite trend was observed for 2-mm samples. Dynamic column experiments showed that oxidation efficiency followed the order KMnO₄ > Na₂S₂O₈/Fe^II > Na₂S₂O₈ whatever the flow condition, whereas the removal extent declined at higher flow rate (e.g., ~50% by KMnO₄ at 0.5 mL/min as compared to ~30% at 2 mL/min). Both HCH removal and oxidant decomposition extents were found higher in saturated columns than the unsaturated ones. While no significant change in relative abundance of soil mineral constituents was observed before and after chemical oxidation, more than 60% of extractable organic matter was lost after chemical oxidation, thereby underscoring the non-selective behavior of chemical oxidation in soil. Due to the complexity of soil system, chemical oxidation has rarely been reported under flow through conditions, and therefore our findings will have promising implications in developing remediation techniques under dynamic conditions closer to field applications.     

Nitrogen fertility and abiotic stresses management in cotton crop: a review

This review outlines nitrogen (N) responses in crop production and potential management decisions to ameliorate abiotic stresses for better crop production. N is a primary constituent of the nucleotides and proteins that are essential for life. Production and application of N fertilizers consume huge amounts of energy, and excess is detrimental to the environment. Therefore, increasing plant N use efficiency (NUE) is important for the development of sustainable agriculture. NUE has a key role in crop yield and can be enhanced by controlling loss of fertilizers by application of humic acid and natural polymers (hydrogels), having high water-holding capacity which can improve plant performance under field conditions. Abiotic stresses such as waterlogging, drought, heat, and salinity are the major limitations for successful crop production. Therefore, integrated management approaches such as addition of aminoethoxyvinylglycine (AVG), the film antitranspirant (di-1-p-menthene and pinolene) nutrients, hydrogels, and phytohormones may provide novel approaches to improve plant tolerance against abiotic stress-induced damage. Moreover, for plant breeders and molecular biologists, it is a challenge to develop cotton cultivars that can tolerate plant abiotic stresses while having high potential NUE for the future.     

Microwave irradiation and citric acid assisted seed germination and phytoextraction of nickel (Ni) by <Emphasis Type="Italic">Brassica napus</Emphasis> L.: morpho-physiological and biochemical alterations under Ni stress

The complex bio-geochemistry of soil allows pollutant to persist for a longer period of time which further decreased the fertility and natural composition of land. Nickel, an inorganic pollutant, coming from a wide range of industrial and manufacturing units possesses serious threat to soil degradation and crop productivity around the world. The present study was carried to evaluate the combined role of microwave irradiation (MR) and citric acid (CA) on the phytoextraction potential of Brassica napus L. under Ni stress. An initial seed germination test was conducted to select effective time scale of MR exposure. Highest seed germination was observed at exposure of 2.45 GHz frequency for 30 s. Healthy seeds of B. napus L. genotype Faisal Canola (RBN-03060) treated with MR at 2.45 GHz for 30 s were sown in plastic pots filled with 5 kg of soil. Nickel and CA applied exogenously in solution form with different combinations to both MR-treated and untreated B. napus plants. The MR-treated plants showed higher growth, biomass, photosynthetic pigments (Chl a, b, total, and carotenoids) and activities of antioxidant enzymes (SOD, POD, APX, CAT) as compared to untreated plants who showed higher reactive oxygen species (MDA, H₂O₂) and electrolyte leakage. Increasing Ni concentration significantly decreased the physiological and biochemical attributes of B. napus both in MR-treated and untreated plants. The addition of CA alleviated Ni-induced toxic effects in both MR-treated and untreated plants by improving antioxidant defense system. The degree of Ni stress mitigation was higher in MR-treated plants. The Ni concentration was higher in root, stem, and leaves of MR-treated plants under CA application as compared to untreated plants. The present study concluded that seeds treated with MR before sowing showed higher accumulation and concentration of Ni from soil, and this phenomenon boosted with the application of CA.     

Phyto-management of Cr-contaminated soils by sunflower hybrids: physiological and biochemical response and metal extractability under Cr stress

Environmental Science and Pollution Research - Chromium (Cr) is a biologically non-essential, carcinogenic and toxic heavy metal. The cultivation of Cr-tolerant genotypes seems the most favorable...     

A study on genotoxicity of textile dyeing industry effluents from Rajshahi,Bangladesh, by the Allium cepa test

Textile dye effluents are believed to be toxic as they might exert various harmful effects on living organisms including genotoxicity. These effluents are the main source of direct and continuous input of pollutants into the aquatic ecosystems. In this study, dye effluents from a local silk dyeing industry were analysed for their genotoxic potential by the Allium cepa genotoxicity test. The A. cepa test is characterised as a genotoxicity test where the roots of A. cepa are grown in different concentrations of the test material. The macroscopic results clearly showed that the toxicity of the dye effluents prompted A. cepa root growth inhibition, and this effect increased with higher concentrations of the effluents. At the cellular level, no dividing cells were found at higher concentrations such as 60%, 80% and 100% of the effluents. However, at a lower concentration of 20%, dividing cells were identified, although the mitotic index was much lower than that of the control. Microscopic analysis showed that the dye effluents induced chromosomal aberrations at significant levels. Taken together, these results revealed that the textile dyeing industry effluents are toxic to eukaryotic cells and these dyes have genotoxic properties that can potentially lead to cancer development and adverse health conditions.     

Production and characterization of biodiesel from Eriobotrya Japonica seed oil: an optimization study

Biodiesel is now-a-days recognized as a real potential alternative to petroleum-derived diesel fuel due to its number of desirable characteristics. However, its higher production cost resulting mainly due to use of costly food-grade vegetable oils as raw materials is the major barrier to its economic viability. Present work is an attempt to explore the potential of Eriobotrya japonica seed oil for the synthesis of biodiesel using alkali-catalyzed transesterification. Optimization of production parameters, namely molar ratio of alcohol to oil, amount of catalyst, reaction time and temperature, was carried out using Taguchi method. Fatty acid composition of both oil and biodiesel was determined using GC and H¹ NMR. Alcohol to oil molar ratio of 6:1, catalyst amount of 1% wt/wt, 2 h reaction time and 50 ^°C reaction temperature were found to be the optimum conditions for obtaining 94.52% biodiesel. Highest % contribution was shown by the ‘amount of catalyst’ (67.32%) followed by molar ratio of alcohol to oil (25.51%). Major fuel properties of E. japonica methyl esters produced under optimum conditions were found within the specified limits of ASTM D6751 for biodiesel, hence it may be considered a prospective substitute of petro-diesel.