Photoactive catalysts for treatment of air pollutants: a bibliometric analysis.

In recent years, photocatalysts are becoming attractive to researchers in exploring their application for treatment of air pollutants. Exposure to ultra-violet visible (UV-VIS) light on photocatalysts often makes them active in decomposing various toxic materials into less or environment-friendly products. Thus, identification, as well as simple synthesis and processing of photocatalysts, could ultimately lead to technologies for the cost-effective mitigation of environmental hazards. A bibliometric analysis has been carried out here to understand and assess the development in photocatalyst research. The data retrieved from the Scopus database on the topic for 2000-2020 were analyzed to investigate the research activities of the past to foresight the future. Various facets of bibliometry were investigated to produce this holistic article. The contribution of various countries, institutions, and authors were investigated. Numerous facets of photocatalyst such as types of photocatalysts, their modification through metal and non-metal doping, their pollutants treatment potency, types of reactors for photocatalysis, factors influencing treatment performance, and models used for designing reactors were examined. In brevity, substantial growth was observed in the last two decades. Contribution of China, the USA, Japan, and India were notable. Chinese universities contributed majorly to the research. Applied Catalysis B: Environmental Journal was the topic's main journal and Titanium dioxide was the hotspot in photocatalytic research. The research development, problem disclosure, adopted strategies, and materials explored on the photocatalysis for air pollution treatment over recent years across the world could be insightful to the researchers and eventually will be beneficial to formulate new research strategies.

Electrocoagulation followed by sound agitation for removal of nitrogen and carbon-based pollutants from industrial wastewater.

The herculean imprecation of nitrogen-based pollutant like ammoniacal nitrogen (AN) and chemical oxygen demand (COD) on aquatic milieu is now a concern for the dye, pharma and fertiliser industries. Wastewater from these is characterised with high concentration of AN, COD and total dissolved solids (TDS), treatment of which is of utmost importance for a cleaner environment. In the current research work, an attempt was made to apply integrated electro-coagulation (EC) - sonication process for the removal of COD and AN from highly acidic dye intermediate wastewater containing high to very high concentration of COD and AN. Systematic laboratory experiments were conducted for the treatment of dye intermediate wastewater and influences of pH (5-11), applied voltage (0.5-4V) and electrolysis time (30-120 min) were investigated. A Response Surface Methodology (RSM) was used for optimization of major operating parameters for EC. The conditions for minimum fraction remaining (C/C0), was found to be same for both COD and AN, i.e. pH 7, time 90 min and applied voltage 2V. The C/Co value for COD and AN were 0.244 and 0.302, respectively. The C/Co value of COD and AN in combined EC-Sonication process with optimum operating conditions were 0.145 and 0.228 respectively with sonication time 60 min at a frequency of 33 kHz. Thus, EC - sonication process is an efficacious process for their removal from dye industrial wastewater.

Role of Azadirachta indica (Neem) and Polyalthia longifolia (Asopalav) trees for improving outdoor thermal environment in unorganized urban settings.

This study assesses the effect of native trees in improving the outdoor thermal environment of an educational institute located in the semi-arid city of Ahmedabad, India. The study area was modelled using ENVI-met and validated against the field measurements. Physical properties of 8 species (55 samples) found in the city were collected. Azadirachta indica (Neem) and Polyalthia longifolia (Asopalav) are among the top 10 species found in the city. The campus has limited space availability and green cover, hence adding more trees is not possible. Hence, two separate scenarios of only those two species were developed by replacing the existing trees. The reduction in air temperature, mean radiant temperature and physiological equivalent temperature (PET) against existing scenario by Asopalav trees at a non-shaded site was found to be up to 1.0 °C, 2.2 °C and 2.0 °C whereas by Neem trees was found to be up to 1.1 °C, 2.3 °C and 2.1 °C. This similarity was likely due to their similar crown widths. The attenuation of direct short-wave radiation by Neem trees was more due to higher Leaf Area Density (LAD). Trees with higher LAD and wider crowns are found to be more useful in improving the outdoor thermal environment in dense urban settings with space constraints.