The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.

https://www.mdpi.com/2073-4441/14/2/242/pdf?version=1642404093

Review on Methylene Blue: Its Properties, Uses, Toxicity and Photodegradation

Bioremediation strategies for chromium removal: Current research, scale-up approach and future perspectives

Biosorption of hexavalent chromium by microorganisms

Environmental deterioration is caused by a variety of pollutants; however, heavy metals are often a major issue. Development and globalization has now also resulted in such pollution occurring in developing societies, including Africa and Asia. This review explores the geographical outlook of soil pollution with heavy metals. Various approaches used to remedy metal-polluted soils include physical, chemical, and biological systems, but many of these methods are not economically viable, and they do not ensure restoration without residual effects. This review evaluates the diverse use of plants and microbes in biotransformation and removal of heavy metals from contaminated soil. Mechanisms on how natural processes utilizing plants (phytoremediation) and microorganisms (bioremediation) remove or reduce heavy metals from soil at various levels are presented. This review concludes that remediation technologies are necessary for the recovery of metal-contaminated environments and the prevention of continuous env...

Biotransformation and removal of heavy metals: a review of phyto and microbial remediation assessment on contaminated soil

Core/shell FeVO4@BiOCl heterojunction as a durable heterogeneous Fenton catalyst for the efficient sonophotocatalytic degradation of p-nitrophenol

Chromium (VI), one of the major pollutants released from tanneries, dye and textile industries, is highly toxic and carcinogenic in nature. Chemical methods for bulk treatment of industrial effluents often fail to reduce the level to meet the environmental regulations. For end of the pipe treatment, bioremediation is considered a better alternative. East Calcutta Wetlands, the major sewage treatment site of Kolkata (previously known as Calcutta), has been reported to be contaminated with several heavy metals including chromium (VI). Therefore, there is a possibility that bacterial population of this region can tolerate chromium (VI) and would be useful for bioremediation of chromium (VI). A strain of Bacillus subtilis isolated from this region was grown in presence of chromium (VI) (2.5 g/L–7.5 5 g/L). There were 97% and 90% reduction of residual chromium concentration in growth media after 24 hours with initial concentrations of 2.5 g/L and 5 g/L respectively. Best removal was observed at 30C. Growth of the Bacillus strain in presence of chromium (VI) was found to be best fit for Tessier model by non-linear regression analysis using MATLAB® 7.4. The Bacillus strain has the potential for the end of the pipe treatment removal of chromium (VI).

/pdf/removal-of-chromium-vi-by-bacillus-subtilis-isolated-from-2uc79lumav.pdf

Removal of Chromium (VI) by Bacillus subtilis Isolated from East Calcutta Wetlands, West Bengal, India

Organic pollutants, like phenol, along with heavy metals, like chromium, are present in various industrial effluents that pose serious health hazard to humans. The present study looked at removal of chromium (VI) in presence of phenol in a counter-current continuous packed bed reactor packed with E. coli cells immobilized on clay chips. The cells removed 85% of 500 mg/L of chromium (VI) from MS media containing glucose. Glucose was then replaced by 500 mg/L phenol. Temperature and pH of the MS media prior to addition of phenol were 30°C and 7, respectively. Hydraulic retention times of phenol- and chromium (VI)-containing synthetic media and air flow rates were varied to study the removal efficiency of the reactor system. Then temperature conditions of the reactor system were varied from 10°C to 50°C, the optimum being 30°C. The pH of the media was varied from pH 1 to pH 12, and the optimum pH was found to be 7. The maximum removal efficiency of 77.7% was achieved for synthetic media containing phenol and chromium (VI) in the continuous reactor system at optimized conditions, namely, hydraulic retention time at 4.44 hr, air flow rate at 2.5 lpm, temperature at 30°C, and pH at 7.

/pdf/performance-study-of-chromium-vi-removal-in-presence-of-i2dxuy736j.pdf

Performance study of chromium (VI) removal in presence of phenol in a continuous packed bed reactor by Escherichia coli isolated from East Calcutta Wetlands.

Kinetic study of degradation of p-nitro phenol by a mixed bacterial culture and its constituent pure strains

Effluent from textile industries contain various azo dyes. Methylene Blue is one of the most predominant one which is hazardous for the environment and has to be degraded chemically or biochemically. A pure culture of Bacillus subtilis and E. coli cells which were already acclimatized to phenol as the sole carbon source were taken for the purpose of the present work. The rate of degradation of MB for E. coli had increased at a much slower rate than that of B. subtilis over the entire degradation period. Hence, in the batch process, overall removal efficiency of Methylene Blue by B. subtilis is higher than that of E. coli. Thus, B. subtilis was taken for further biodegradation of Methylene Blue studies in a continuous process in a counter current packed bed reactor packed with clay chips. In addition to a packing material, the clay chips also act as a whole cell immobilizing matrix for the Bacillus cells. The effect of Methylene Blue flow rate and air flow rate on percentage Methylene Blue removal ...

Biochemical degradation of Methylene Blue using a continuous reactor packed with solid waste by E. coli and Bacillus subtilis isolated from wetland soil.

The potential of a mixed consortium of bacteria has been isolated from the soil of the East Calcutta Wetlands, the major waste treatment and recovery site of Kolkata, for degradation of phenol, a representative of phenolic compounds has been investigated. The mixed culture is first acclimatized to higher phenol concentrations in the mineral salt (MS) media and then its behaviour for degradation of phenol has been studied. The mixed culture successfully degrades phenol till 200 mg/L and then undergoes substrate inhibition at 400 mg/L. At still higher phenol concentration of 800 mg/L this mixed culture shows an anomalous behaviour by degrading phenol at a higher rate as compared to lesser phenol concentration by overcoming the substrate inhibition effect. The bacterial growth curve also follows the same pattern which indicates the observation. By the kinetic modeling of the substrate inhibition biokinetic constants are calculated which conform to experimentally observed values. For the phenol degradation and growth studies, Haldane model and Yano and Koga model are found to be the most efficient kinetic models respectively.

http://nopr.niscair.res.in/bitstream/123456789/33523/1/IJCT%2022%285%29%20227-233.pdf

Bhaswati Chakraborty

Papers

Removal of Chromium (VI) by Bacillus subtilis Isolated from East Calcutta Wetlands, West Bengal, India

Performance study of chromium (VI) removal in presence of phenol in a continuous packed bed reactor by Escherichia coli isolated from East Calcutta Wetlands.

Kinetic study of degradation of p-nitro phenol by a mixed bacterial culture and its constituent pure strains

Biochemical degradation of Methylene Blue using a continuous reactor packed with solid waste by E. coli and Bacillus subtilis isolated from wetland soil.

Study of phenol biodegradation by an indigenous mixed consortium of bacteria