A review on application of dielectric barrier discharge plasma technology on the abatement of volatile organic compounds

• Applications of non-thermal plasma reactors for reduction of VOCs were reviewed. • Dielectric barrier discharge (DBD) plasma was considered. • Effect of process parameters was studied. • Effect of catalysts and inhibitors were evaluated. Volatile organic compounds (VOCs) released from the waste treatment facilities have become a significant issue because they are not only causing odor nuisance but may also hazard to human health. Non-thermal plasma (NTP) technologies are newly developed methods and became a research trend in recent years regarding the removal of VOCs from the air environment. Due to its unique characteristics, such as bulk homogenized volume, plasma with high reaction efficiency dielectric barrier discharge (DBD) technology is considered one of the most promising techniques of NTP. This paper reviews recent progress of DBD plasma technology for abatement of VOCs. The principle of plasma generation in DBD and its configurations (electrode, discharge gap, dielectric barrier material, etc.) are discussed in details. Based on previously published literature, attention has been paid on the effect of DBD configuration on the removal of VOCs. The removal efficiency of VOCs in DBD reactors is presented too, considering various process parameters such as initial concentration, gas feeding rate, oxygen content and input power. Moreover, using DBD technology, the role of catalysis and inhibitors in VOCs removal are discussed. Finally, a modified configuration of the DBD reactor, i.e. double dielectric barrier discharge (DDBD) for the abatement of VOCs is discussed in details. It was suggested that the DDBD plasma reactor could be used for higher conversion efficiency as well as for avoiding solid residue deposition on the electrode. These depositions can interfere with the performance of the reactor.     

Unraveling prevalence and public health risks of arsenic,uranium and co-occurring trace metals in groundwater along riverine ecosystem in Sindh and Punjab,Pakistan

Environmental Geochemistry and Health - The current study focuses on the understanding of contamination status, distribution, source apportionment and health perspectives of arsenic (As), uranium...     

Complexing agents for metal removal using ultrafiltration membranes: a review

Environmental Chemistry Letters - Water pollution by human activities is major issue. In particular, toxic metals are of particular concern, thus calling for advanced methods to remove metals from...     

Fate of carbosulfan and monocrotophos in sandy loam soils of Pakistan under field conditions at different watertable depths

Information regarding pesticide mobility is critical for the evaluation of pesticide management practices. For this purpose, lysimetric studies were conducted to develop assessment schemes to protect groundwater from unacceptable effects caused by pesticide use. By using these studies, specific monitoring actions and prevention measures for the protection of waters can be studied, and the results thus obtained can provide the local authorities and the decision makers with an identification tool for demarcating risk areas. Pesticide residues were found at the bottom of lysimeters in the following pattern i.e., 1.52 > 2.1 > 2.74 m which could represent an "index of risk" for groundwater pollution. Regressions built for carbofuran and monocrotophos against watertable depths showed a decreasing trend of pesticide in higher watertable treatments. These findings support the existence of a significant role for chromatographic flow in sandy texture soil. Moreover, the higher values of pesticide residue at the bottom of lysimeters reflect that chromatographic flow as well as preferential flow pattern prevails during higher precipitation events. The precipitation received during the study was higher than the 10 year average and can be considered relatively as a worst case scenario. Finally, the authors have recommended a standardized pesticide monitoring scheme for groundwater in accordance with the already validated generic schemes in developed countries.     

Lung function decrement with arsenic exposure to drinking groundwater along River Indus: a comparative cross-sectional study

This study was designed to determine the association between chronic arsenic exposure through drinking groundwater and decrement in lung function, particularly among individuals who do not have signs of arsenic lesions, among an adult population. This was a comparative cross-sectional study conducted during the months of January to March 2009. One hundred participants ≥15 years of age in each group, i.e. exposed (≥100 μg/l) and unexposed (≤10 μg/l) to arsenic, determined by testing drinking water samples (using portable kits), were compared for effects on lung function using spirometry. A structured and validated questionnaire was administered. Examination for arsenic skin lesions was also done. There was a decline in the mean adjusted FEV1 of 154.3 ml (95% CI: −324.7, 16.0; p = 0.076), in mean adjusted FVC of 221.9 ml (95% CI: −419.5, −24.3; p = 0.028), and in FEV1/FVC ratio of 2.0 (95% CI: −25.3, 29.4; p = 0.884) among participants who were exposed to arsenic compared to those unexposed. A separate model comprising a total of 160 participants, 60 exposed to arsenic concentrations ≥250 μg/l and 100 unexposed at arsenic concentrations of ≤10 μg/l, showed a decrement in mean adjusted FEV1 of 226.4 ml (95% CI: −430.4, −22.4; p = 0.030), in mean adjusted FVC of 354.8 ml (95% CI: −583.6, −126.0; p = 0.003), and in FEV1/FVC ratio of 9.9 (95% CI: −21.8, 41.6; p = 0.539) among participants who were exposed to arsenic in drinking groundwater. This study demonstrated that decrement in lung function is associated with chronic exposure to arsenic in drinking groundwater, occurring independently, and even before any manifestation, of arsenic skin lesions or respiratory symptoms. The study also demonstrated a dose-response effect of arsenic exposure and lung function decrement.     

From socioeconomic disparity to environmental injustice: the relationship between housing unit density and community green space in a medium city in Pakistan

Rapid urbanisation, lack of proactive planning and improper allocation of resources may result in socio-economic disparity among and within cities, causing social unrest and environmental injustice in the neighbourhoods. This study aims to examine whether the planning standards for housing schemes in Pakistan are able to maintain equitable access to green spaces within the cities. Ten residential sites in Sheikhupura city with different housing unit sizes and densities were selected for the study. The supply of urban green infrastructure in housing scheme has been assessed: (i) by comparing the percentage of green spaces, including community parks and open spaces and street landscape; and (ii) by calculating per dwelling unit and per capita share of green spaces. These indicators have been studied against the housing density and population density of the schemes by applying correlation and linear regression models. The results show that all the housing schemes plans provide for similar amounts of green space as a percentage of total area. The per capita share of green spaces is very low in high-density areas, but interestingly, the street landscape has a higher potential to contribute to the overall landscape in high-density neighbourhoods, compensating for low per capita green space. Housing unit density and population density must be incorporated in planning standards so planners can effectively devise a mix of community parks, street landscape and private green spaces to help maintain per capita green spaces, and hence environmental resource equality in different parts of the city.     

Characterization and physicochemical aspects of novel cellulose-based layered double hydroxide nanocomposite for removal of antimony and fluoride from aqueous solution

A series of novel adsorbents composed of cellulose (CL) with Ca/Al layered double hydroxide (CC_xA; where x represent the Ca/Al molar ratio) were prepared for the adsorption of antimony (Sb(V)) and fluoride (F^?) ions from aqueous solutions. The CC_xA was characterized by Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), elemental analysis (CHNS/O), thermogravimetric analysis (TGA-DTA), zeta potential, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis. The effects of varying parameters such as dose, pH, contact time, temperature and initial concentration on the adsorption process were investigated. According to the obtained results, the adsorption processes were described by a pseudo-second-order kinetic model. Langmuir adsorption isotherm model provided the best fit for the experimental data and was used to describe isotherm constants. The maximum adsorption capacity was found to be 77.2 and 63.1 mg/g for Sb(V) and F^?, respectively by CC₃A (experimental conditions: pH 5.5, time 60 min, dose 15 mg/10 mL, temperature 298 K). The CC₃A nanocomposite was able to reduce the Sb(V) and F^? ions concentration in synthetic solution to lower than 6 μg/L and 1.5 mg/L, respectively, which are maximum contaminant levels of these elements in drinking water according to WHO guidelines.     

Destruction of VOCs by combination of corona discharge and catalysis techniques

The catalytic effect of alumina on the destruction of toluene, benzene, acetone and methanol, in DC pulsed corona discharge reactor was studied. In the presence of alumina the inlet concentration of the VOCs was varied from 5 x 10-6 mol/L to 80% x 10-6 mol/L, and their decomposition efficiency (conversion %) was found to be 99%-80% for toluene, 99%-97% for benzene, 95%-92% for acetone, and 72%-85% for methanol. Corresponding decomposition in the absence of alumina was 90%-38% for toluene, 89%-57% forbenzene, 42%-30% for acetone, and 47%-19% for methanol. Feed gas flow rate was 400 cm3/min and power reading from DC source was 7.4 W in all of the experiments. Alumina also shifted the CO/CO2 ratio in the by-products in favor of CO2. Ozone concentration at the reactor outlet was higher in the presence of alumina. Enhancement in VOCs decomposition by alumina was explained on the basis of higher concentration of ozone and its precursor atomic oxygen [O].Decomposition efficiency (conversion %) for individual compounds was found to be inversely proportional to the ionization potential of the compound, under identical conditions. Double DC high voltage sources pulse generator was tested and found to improve VOCs decomposition compared with the conventional single DC high voltage source.     

Enzymatic production of biosilica glass using enzymes from sponges: basic aspects and application in nanobiotechnology (material sciences and medicine)

Biomineralization, biosilicification in particular (i.e. the formation of biogenic silica, SiO₂), has become an exciting source of inspiration for the development of novel bionic approaches following “nature as model”. Siliceous sponges are unique among silica forming organisms in their ability to catalyze silica formation using a specific enzyme termed silicatein. In this study, we review the present state of knowledge on silicatein-mediated “biosilica” formation in marine sponges, the involvement of further molecules in silica metabolism and their potential application in nanobiotechnology and medicine. Werner E. G. Müller dedicated this study to Prof. Vera Gamulin (Rudjer Boskovic Institute, Zagreb, Croatia) in honour of her unique contributions in molecular evolution.