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Ultrasound cavitation is an advanced oxidation process in which organic contaminants are degraded by thermal degradation and reaction with hydroxyl (OH∙) radicals. In the present study, a horn-type sonicator was used to treat the synthetic aqueous solution containing phenol, and the effect of various parameters such as ultrasonic power, initial solution pH, and tip or horn depth on the degradation of phenol in synthetic aqueous solution was investigated, and the optimum value of the parameters was determined. It was observed that the degradation of phenol increased with an increase in ultrasonic power. The degradation of phenol was higher in acidic solution pH compared with that in alkaline solution pH. Moreover, the degradation of phenol increased with an increase in tip depth until an optimum value was reached, beyond which the degradation of phenol decreased with an increase in tip depth. To enhance the phenol degradation, the ultrasound cavitation of synthetic aqueous solution containing phenol was performed by adding hydrogen peroxide and Fenton reagent to the synthetic aqueous solution, and an enhancement in phenol degradation was noticed. Furthermore, cavitation energy was determined, and an enhancement in the energy efficiency of the ultrasound cavitation in the presence of hydrogen peroxide and Fenton reagent was observed. The treatment of industrial effluent containing phenol was also performed, and a chemical oxygen demand reduction of 56.6% was obtained after 120 min. The cost of effluent treatment was determined. [ABSTRACT FROM AUTHOR]

The performance of electrocoagulation (EC) was studied by conducting experiments for the removal of Reactive Orange 4 dye from its synthetic aqueous solution. The effect of operational parameters (initial solution pH, current density, inter-electrode distance, electrolysis time and retention time, solution temperature, conductivity and different electrode combinations) on the efficiency of EC was studied and the results were analysed in terms of colour removal efficiency (CRE), electrical energy consumption (EEC) and operating cost (OC). The effect of different anions on the efficiency of EC was studied by conducting experiments with electrolytes containing chloride, sulphate, carbonate and nitrate ions. The characterisation of EC generated sludge was performed using XRD. A maximum CRE of 95% was obtained for EEC of 1.7 kWh/m3 and OC of 0.45 US $/m3. It was found that the addition of electrolyte containing chloride ions resulted in higher CRE (93–95%) compared to electrolytes containing sulphate and carbonate ions as their presence can lead to passivation of the electrode surface & thereby resulting in a reduction in CRE (60% and 41%, respectively). The addition of sodium chloride as an electrolyte resulted in minimum EEC and OC. The Al/Al electrode combination provided the maximum CRE and least EEC & OC. The increase in solution temperature leads to reduction in CRE and CE due to formation of passive layer on the surface of electrodes. However, a reduction in cell potential and EEC was noticed with an increase in solution temperature. [ABSTRACT FROM AUTHOR]

In Northern India, a large quantity of rice stubble is burned in situ in agricultural fields after the rice crop has been harvested, which releases harmful gases and particulate matter into the environment. This poses a threat to the environment and the health of living organisms. Stubble burning could be prevented by utilizing the rice straw directly or indirectly. In this study, efforts have been made to explore the use of biochar that is obtained from the pyrolysis of rice straw as an adsorbent for the removal of arsenic from water, because arsenic in groundwater is a worldwide problem. The rice straw was chemically modified and pyrolyzed to obtain iron-modified biochar. The iron-modified biochar was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis. The adsorption optimization for the arsenic removal was carried out using response surface methodology for three adsorption parameters (e.g., contact time, adsorbent dosage, and initial arsenic concentration). The iron-modified biochar could remove 99% of the arsenic from water with 989 µg/L arsenic at an adsorbent dosage of 3.25 g/L. The leaching of iron from the iron-modified biochar was tested and was negligible. In addition, the disposal of exhausted adsorbent in municipal solid waste landfills was suggested following the toxicity characteristic leaching procedure. [ABSTRACT FROM AUTHOR]

In the present study, sustainable upscaling of rice straw, an agri‐residue, is explored as the way to obtain active material to prepare anode for use in lithium‐ion batteries (LIBs). The biochar having high carbon and low silica content is prepared by initial chemical treatment of rice straw followed by its pyrolysis. The pristine and modified biochar are characterized using Brunauer‐Emmett‐Teller surface area, energy dispersive X‐ray spectroscopy, carbon hydrogen nitrogen sulphur elemental analysis, scanning electron microscopy, X‐Ray power diffraction, Fourier transform infrared spectroscopy and Raman analysis and the modified biochar show an enhancement in graphitic carbon content. A coin cell is assembled using anode prepared from modified biochar. The coin cell is subjected to electrochemical testing and had a discharge capacity of 352 mA.h g−1. Further, the coin cell is tested for 100 cycles and a columbic efficiency of 99.7% was obtained. Therefore, biochar derived from pyrolysis of rice straw has the potential to be used as anode material for LIBs. [ABSTRACT FROM AUTHOR]