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E-waste an urban environmental pollution: problems and prospects in developing countries
Get PDFElectronic waste or E-waste comprises of old, end-of-life electronic appliances such as computers, laptops, TVs, DVD players, refrigerators, freezers, mobile phones, MP3 players etc. which have been disposed of by their original users. E-waste contains many hazardous constituents that may negatively impact the environment and affect human health if not properly managed. The problem of E-waste has forced Environmental agencies of many countries to innovate, develop and adopt environmentally sound options and strategies for E-waste management, with a view to mitigate and control the ever growing threat of E-waste to the environment and human health. E-waste management is given the top priority in many developed countries, but in rapid developing countries like India, it is difficult to completely adopt or replicate the E-waste management system followed in developed countries due to many country specific issues viz. socio-economic conditions, lack of infrastructure, absence of appropriate legislations for E-waste, approach and commitments of the concerned, etc.
The paper presents E-waste scenario in developing countries, E-waste composition, categorization, prospects of recoverable, recyclable and hazardous materials found in the E-waste, recycling and recovery options followed. And the overview and need of the laws and regulation related to E-waste for better E-waste Management
Management of various organic fractions of municipal solid waste via recourse to VFA and biogas generation
No full textA hybrid anaerobic solid–liquid system was used for anaerobic digestion of organic fraction of municipal solid waste
(OFMSW) consisting of mixed food+fruit waste and vegetable waste. Hydrolysis and acidogenesis potential of the above
wastes were evaluated with the aim of producing value-added products in the form of volatile fatty acids (VFAs) and biogas
recovery. Efficient hydrolysis and acidogenesis of mixed food+fruit waste was observed at a hydraulic retention time (HRT)
of 1–3 d with a five-fold increase in soluble chemical oxygen demand (SCOD) followed by VFA production consisting
of 50–75% acetic acid. Longer time was required for hydrolysis of vegetable waste with optimum hydrolysis and SCOD
generation at 9 d HRT followed by VFA synthesis consisting of 45% acetic acid. Higher inoculum:substrate ratios resulted
in improved hydrolysis and acidogenesis rates for vegetable waste in shorter time of 6 d with higher VFA production and
increase in acetic acid content to 70%. When acidogenic leachate was fed into methanogenic reactors, detectable biogas
production was observed after 25 d with 37–53% SCOD removal from leachate from mixed food+fruit waste and methane
production of 0.066–0.1 L g−1 SCOD removed and methane content of 38%. Though biogas yield from acidogenic leachate
from vegetable waste was lower, nearly 94% volatile solids (VS) removal was observed in the reactors thereby providing
methane yield of 0.13–0.21 L g−1 VS consumed. Thus, the study provided a method for generation of value-added products
from an otherwise misplaced resource in the form of OFMSW
Nano cobalt oxides for photocatalytic hydrogen production
No full textNano structured metal oxides including TiO2, Co3O4 and Fe3O4 have been synthesized and
evaluated for their photocatalytic activity for hydrogen generation. The photocatalytic
activity of nano cobalt oxide was then compared with two other nano structured metal
oxides namely TiO2 and Fe3O4. The synthesized nano cobalt oxide was characterized
thoroughly with respect to EDX and TEM. The yield of hydrogen was observed to be 900,
2000 and 8275 mmol h�1 g�1 of photocatalyst for TiO2, Co3O4 and Fe3O4 respectively under
visible light. It was observed that the hydrogen yield in case of nano cobalt oxide was more
than twice to that of TiO2 and the hydrogen yield of nano Fe3O4 was nearly four times as
compared to nano Co3O4. The influence of various operating parameters in hydrogen
generation by nano cobalt oxide was then studied in detail
Defluoridation of water using calcium aluminate material
No full textA new calcium aluminate (CA) type material has been synthesized using combustion method, which
offers formation of smaller particles with open pores. The material thus synthesized has been studied
for its fluoride uptake properties in simulated and actual drinking waters, containing fluoride as well
as other co-anions. The adsorbent shows high adsorption capacity for fluoride and it is possible to effectively
remove fluoride to the tune of 85% from initial concentration of 8.9 mg L�1 and using a dose of
3 g L�1. Kinetics of the adsorption system has been studied indicating that the intra-particle diffusion
contributes to the rate determining step. The experimental data fitted well into Langmuir adsorption isotherm
and follows pseudo-second-order kinetics. The thermodynamic parameters suggest the complex
nature of fluoride uptake reaction, dominated by chemisorption. These studies also infer that fluoride
adsorption on CA is spontaneous and an endothermic process. The effective regeneration was achieved
by treating the fluoride loaded material by NaOH and H2SO4. CA show potential for defluoridation of
water, especially in presence of other anions, when selectivity for fluoride is of prime importance. This
class of material suggest the possibility of tailoring of their properties and therefore, likely to attract
for attention for defluoridation of water
Influence of CO 2 concentration on carbon concentrating mechanisms in cyanobacteria and green algae: a proteomic approach
Get PDFCarbon concentrating mechanisms play a vital role in photosynthesis in microalgae and cyanobacteria especially in the proper functioning of Rubisco and assimilation of carbon via the Calvin cycle. This study evaluates the role of carbon dioxide on carbon concentrating mechanism (CCM) in a cynaobacteria, Spirulina platensis and a microalga, Chlorella sp. 786. The study organisms were grown in both atmospheric (control sample, 0.035%) and high (exposed sample, 10%) CO2 concentrations. Second dimension (2D) electrophoresis revealed a huge difference in the protein profiles of both organisms suggesting the induction of CCM related proteins in the sample maintained at atmospheric CO2 concentration and the repression of CCM related proteins in the sample maintained at 10% CO2. Liquid chromatography-mass spectroscopy analysis revealed the presence of two important Ci transporter proteins in the control sample of S. platensis, namely ferredoxin-NADP+ reductase and ATP binding cassette (ABC) transport system protein. These proteins were only expressed in the control sample and were downregulated or not expressed at all in the exposed sample. Consequently, this study conclusively proves that CCMs are only inducted at low CO2 concentrations and are not functional at high CO2 concentration
NMR studies of Carbon Dioxide and Methane Self Diffusion in ZIF-8 at elevated gas pressures
No full textSelf-diffusion measurements with methane and carbon dioxide adsorbed in the Zeolitic Imidazolate Frame-work-8 (ZIF-8) were performed by 1H and 13C pulsed field gradient nuclear magnetic resonance (PFG NMR). The ex-periments were conducted at 298 K and variable pressures of 7 to 15 bar in the gas phase above the ZIF-8 bed. Via known adsorption isotherms these pressures were converted to loadings of the adsorbed molecules. The self-diffusion coefficients of carbon dioxide measured by PFG NMR are found to be independent of loading. They are in good agree-ment with results from molecular dynamic (MD) simula-tions and resume the trend previously found by IR mi-croscopy at lower loadings. Methane diffuses in ZIF-8 only slightly slower than carbon dioxide. Its experimentally ob-tained self-diffusion coefficients are about a factor of two smaller than the corresponding values determined by MD simulations using flexible framework
Particulate matter and elemental emissions from a cement kiln
No full textParticulatematter emission froma stack attached to the kiln and rawmill in a cement plantwas studied. Elemental(As, Cd, Co, Cr, Cu, Fe,Mn, Ni, Pb and Zn) and ionic (Ca2+, NO3−, SO42−) composition and particle size distribution of stack particulates, principal rawmaterials and products were determined. The feed rates of raw meal were found to be 144 and 18 t h−1 at cyclone and bag house inlets, respectively, while stack emission of the same amounted to 86 kg h−1, indicating bag filter removal efficiency of over 99%. Particle size distribution of stack particulates revealed that PM10, PM2.4 and PM1 had cumulative shares of 88%, 49% and 15%, respectively. Emission load of various elements fromthe stack ranged from0.001 (copper) to 1.69 (iron) kg h−1. Air quality modelling indicated that maximum ground level concentrations of As, Pb, Ni, Cd and Cr were much lower than the prescribed ambient air quality standards in India and also the Health Guidelines of USEPA and others. Particle size distribution and the elemental content of the raw materials, by-products and cement indicated that elemental exposure is likely from fugitive emissions during improper material handling and transport
SILICA GEL SUPPORTED TITANIUM DIOXIDE PHOTOCATALYST FOR METHYL ORANGE PHOTOREDUCTION
No full textTiO2 based photocatalysis has been widely investigated and has vital applications in energy and environmental remediation processes.
In this connection research is being conducted in the zone of supported TiO2 based photocatalysts for development of visible light
induced photocatalytic material. A series of materials were synthesized including zeolite based composite photocatalyst, N-doped mesopourous
titania and investigated for dye degradation followed by hydrogen generation. Current research trend is towards supported photocatalyst
therefore silica gel supported TiO2 photocatalyst was designed and developed also compared with alumina based photocatalyst.
From the experimental data it was found that Silica based system has edge over the other synthesized photocatalysts with effective dye
degradation of about 9.61 mg of MO reduced per g of TiO2 (0.508 mg of MO reduced per g of TiO2 for Degussa P-25). MO photoreduction is
19 times higher as compared to benchmark material Degussa P-25. Results well illustrate the formation of high dispersed metal oxide on
silica framework
Tyrosinase-Immobilized MCM-41 for the Detection of Phenol
No full textIn the present investigation, we report the
immobilization of the enzyme tyrosinase on mesoporous
silica material, i.e. MCM-41 to serve as a tool for
the detection of phenol. The enzyme immobilized onto
the MCM-41 matrix has shown to retain its activity and
is quite stable. The immobilization of enzyme has been
discussed, and the various factors that affect the loading
of enzyme onto MCM-41 were studied and optimized.
The applicability of tyrosinase-immobilized MCM-41
was then demonstrated for the detection of phenol. The
lowest detectable concentration of phenol by tyrosinaseimmobilized
MCM-41 was observed to be 1 mg l−1.
The factors influencing the detection of phenol were
then studied in detail
Hydrogen delivery through liquid organic hydrides: Considerations for a potential technology
No full textCarrying hydrogen in chemically bounded form as cycloalkanes and recovery of hydrogen
via a subsequent dehydrogenation reaction is a potential option for hydrogen transport
and delivery. We have earlier reported a novel method for transportation and delivery of
hydrogen through liquid organic hydrides (LOH) such as cycloalkanes. The candidate
cycloalkanes including cyclohexane, methylcyclohexane, decalin etc. contains 6 to 8 wt%
hydrogen with volume basis capacity of hydrogen storage of 60e62 kg/m3. In view of
several advantages of the system such as transportation by present infrastructure of
lorries, no specific temperature pressure requirement and recyclable reactants/products,
the LOH definitely pose for a potential technology for hydrogen delivery. A considerable
development is reported in this field regarding various aspects of the catalytic dehydrogenation
of the cycloalkanes for activity, selectivity and stability. We have earlier reported
an account of development in chemical hydrides. This article reports a state-of-art in LOH
as hydrogen carrier related to dehydrogenation catalysts, supports, reactors, kinetics,
thermodynamic aspects, potential demand of technology in field, patent literature etc