Electrochemical oxidation of p-nitrophenol was examined using differentanodic materials, including T/boron-doped diamond (BDD), Ti/SnO2-Sb/PbO2, and Ti/SnO2-Sb anodes. The results demonstrated that Ti/BDD anodes had a much stronger mineralization performance than the other two anodes. Furthermore, it was found that hydroxyl radicals could mainly exist as free hydroxyl radicals at BDD anodes, which could react with organic compounds effectively. This implied that the dominant mechanism for a much higher mineralization capacity of BDD anodes would be attributed to the existence of free hydroxyl radicals in the BDD anode cell rather than adsorbed hydroxyl radicals on the BDD anode. To further corroborate this hypothesis, electrochemical oxidation of p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) was examined at the Ti/BDD, Ti/SnO2-Sb/ PbO2, and Ti/SnO2-Sb anodes, respectively. The study revealed that for Ti/BDD electrodes, the degradation rate of p-substituted phenols (k) increased with the increase of Hammett's constant (sigma), which confirmed the dominance of free hydroxyl radicals at BDD anodes and its effective reaction with organics therein. For Ti/SnO2-Sb/PbO2 electrodes, the degradation rate of p-substituted phenols (k) increased with the increase of initial surface concentration gamma (representing the adsorption capacity of phenols to electrode surface), which indicated that organic compounds mainly reacted with adsorbed hydroxyl radicals at PbO2 anodes. For Ti/SnO2-Sb electrodes, however, k increased with the increase of the integrated parameter S (representing the effects of both sigma and gamma), which implied that organic compounds reacted with both adsorbed hydroxyl radicals and free hydroxyl radicals at SnO2 anodes.

Essential explanation of the strong mineralization performance of boron-doped diamond electrodes / Environ. Sci. Technol.

Clean and safe water is a fundamental human need for multi-faceted development of society and a thriving economy. Brisk rises in populations, expanding industrialization, urbanization and extensive agriculture practices have resulted in the generation of wastewater which have not only made the water dirty or polluted, but also deadly. Millions of people die every year due to diseases communicated through consumption of water contaminated by deleterious pathogens. Although various methods for wastewater treatment have been explored in the last few decades but their use is restrained by many limitations including use of chemicals, formation of disinfection by-products (DBPs), time consumption and expensiveness. Nanotechnology, manipulation of matter at a molecular or an atomic level to craft new structures, devices and systems having superior electronic, optical, magnetic, conductive and mechanical properties, is emerging as a promising technology, which has demonstrated remarkable feats in various fields including wastewater treatment. Nanomaterials encompass a high surface to volume ratio, a high sensitivity and reactivity, a high adsorption capacity, and ease of functionalization which makes them suitable for application in wastewater treatment. In this article we have reviewed the techniques being developed for wastewater treatment using nanotechnology based on adsorption and biosorption, nanofiltration, photocatalysis, disinfection and sensing technology. Furthermore, this review also highlights the fate of the nanomaterials in wastewater treatment as well as risks associated with their use.

https://www.mdpi.com/1420-3049/26/6/1797/pdf

Nanotechnology in Wastewater Management: A New Paradigm Towards Wastewater Treatment.

A crucial review on polycyclic aromatic Hydrocarbons - Environmental occurrence and strategies for microbial degradation.

Distributions of arsenic and other heavy metals, and health risk assessments for groundwater in the Guanzhong Plain region of China

Human health risk assessment of ground water contaminated with petroleum PAHs using Monte Carlo simulations: A case study of an Indian metropolitan city.

Human health risk assessment for exposure to BTEXN in an urban aquifer using deterministic and probabilistic methods: A case study of Chennai city, India.

Comprehensive treatment of urban wastewaters using electrochemical advanced oxidation process

Investigating the degradation of nC12 to nC23 alkanes and PAHs in petroleum- contaminated water by electrochemical advanced oxidation process using an inexpensive Ti/Sb-SnO2/PbO2 anode

Incidences of leakages of chemicals from underground oil storage tanks or oil-carrying pipelines have posed huge threat to the coastal aquifers around the world. One such leak was recently identified and notified by the people of Tondiarpet, Chennai, India. The assessment of the contamination level was done by obtaining electrical resistivity maps of the subsurface, drilling of 20 new borewells for soil and water analysis, and testing the water quality of 30 existing borewells. Samples were collected from the borewells, and observations were made that included parameters such as odor, moisture, contamination characteristics, lithology, groundwater level, thickness of the free product that are used to demarcate the extent of soil, and water contamination. Furthermore, a multigas detector was used to detect hydrocarbon presence as soil vapor. Moreover, to capture the transport of dissolved hydrocarbons, 10 samples were collected in the periphery of the study area and were analyzed for the presence of petroleum hydrocarbon and polyaromatic hydrocarbon. Analysis of the data indicated the presence of free-phase hydrocarbon in soil and groundwater close to the junction of Thiruvottiyur high (TH) road (TH) and Varadaja Perumal Koil (VPK) street. Although the contaminant plume is confined to a limited area, it has spread more to the southern and eastern side of the pipeline possibly due to continuous abstraction of groundwater by residential apartments. After cutting a trench along the VPK street and plotting of the plume delineation map, observations indicated that the source of the hydrocarbon leak is present in VPK street close to TH road. A multipronged strategy was suggested targeting the remediation of oil in various phases.

Bokam Rajasekhar

Papers

Human health risk assessment of ground water contaminated with petroleum PAHs using Monte Carlo simulations: A case study of an Indian metropolitan city.

Human health risk assessment for exposure to BTEXN in an urban aquifer using deterministic and probabilistic methods: A case study of Chennai city, India.

Comprehensive treatment of urban wastewaters using electrochemical advanced oxidation process

Investigating the degradation of nC12 to nC23 alkanes and PAHs in petroleum- contaminated water by electrochemical advanced oxidation process using an inexpensive Ti/Sb-SnO2/PbO2 anode

An assessment of subsurface contamination of an urban coastal aquifer due to oil spill