Waste-water treatment by microwave irradiated exfoliated graphite
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Date
2022-09
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G.B. Pant University of Agriculture and Technology, Pantnagar, District Udham Singh Nagar, Uttarakhand. PIN - 263145
Abstract
Oil is widely used in many industries, household needs, and for ignition purposes, whereas dyes are largely used by industries for colouring purposes. Due to their great use, the discharge of wastewater containing oil and dyes to water bodies and accidental oil spills cause enamours damage to the environment. The serious impact of wastewater led to the utmost urgency to treat wastewater containing oil and dye. Exfoliated graphite (EG) has gotten high attention for adsorbing oil from oily water and titanium dioxide (TiO2) nanoparticles have shown great potential to work as an excellent photocatalyst in dye degradation. Therefore in order to treat wastewater containing both oil and dye as pollutants, the present work is an effort to synthesize the composite of EG and TiO2 nanoparticles. EG has been synthesized by exfoliation of GIC by microwave irradiation. GIC has been prepared by chemical intercalation technique. Different EG samples have been prepared by varying exfoliation times. An oil adsorption study has been performed for mustard oil, diesel oil, and engine oil on different EG samples for different contact times. The results revealed that EG adsorbs oil up to its maximum capacity within 5 minutes. The adsorption capacity of different EG samples on different oil has been calculated and it is concluded that an exfoliation time of 1.5 minutes (sample EG3) is sufficient to achieve maximum adsorption capacity and a further increase in exfoliation time makes no change in adsorption capacity indicating that complete exfoliation has been achieved in 1.5 minutes. For each EG sample, adsorption has been found to be directly proportional to the viscosity of the oil. TiO2 nanoparticles have been synthesized by the sol-gel method. UV visible spectra of TiO2 nanoparticles show high absorption in the UV region. EG3/TiO2 composite has been synthesized by exfoliating TiO2-loaded GIC for 1.5 minutes. The synthesized materials have been characterized by XRD, FTIR, FESEM, and gas adsorption isotherm. XRD and FTIR study shows the presence of EG and TiO2 in the composite and no chemical reaction has occurred between them. From the FESEM image, it has been confirmed that the composite has a porous structure just like EG3, with TiO2 particles present on its surface. From the gas adsorption isotherm, the specific surface area of EG3 and EG3/TiO2 composite has been found out 12.5 m2/g and 47.7295 m2/g respectively. Pore size distribution shows a large number of micropores present in EG and EG3/TiO2 composite. A comparative study of EG3, TiO2 nanoparticles, and EG3/TiO2 composite for treatment of oil and dye polluted wastewater has been performed in direct sunlight. Dye degradation has been studied by UV visible spectroscopy of treated water with different materials. The results show that EG3 has removed only oil, TiO2 nanoparticles are only able to degrade dye but EG/TiO2 composite is able to remove oil as well as to degrade dye from the polluted water. Hence, the EG3/TiO2 composite proposed in the present work can be a novel material for the treatment of both oil and dye polluted wastewater.