Abstract
In this study, a magnetic titanium nanotube/carbon nanotube nanocomposite (magnetite TNT@CNT nanocomposite) was developed and its efficiency was evaluated towards oxidative degradation of Bisphenol A (BPA) from high saline polycarbonate plant wastewater (PCW) using catalytic wet peroxide oxidation (CWPO). The characterization of the nanocomposite was performed using XRD, SEM, BET surface area, FT-IR, and VSM analysis. The effects of operating conditions, including solution pH, H2O2 dosage, reaction temperature and catalyst loading, were optimized in the CWPO process for degradation of BPA in the PCW. In the best obtained experimental condition, at pH of 6.30, H2O2 dosage of 2.5 g/L, temperature of 70 °C and 100 mg/L of catalyst dosage, CWPO process exhibits the best catalytic performance with the complete BPA degradation, 68.78% of COD removal and 47.14% of TOC reduction for PCW being obtained. The role of hydroxyl radicals in the reaction mechanism was shown by indirect analysis i.e. tert Butanol (tBuOH) scavenging experiment. Under the optimum experimental conditions, the stability and reusability of the nanocomposite was demonstrated with slight decline (<10% reduction) in the CWPO after four consecutive runs in terms of its catalytic activity. The fate of organic pollutants in the treated PCW by CWPO was identified by qualitative GC/MS analysis. The biodegradability of the treated PCW increased during the CWPO process with a 4-fold increase of the BOD5/COD ratio being obtained, namely from 0.1 (indicating non-biodegradability) to 0.43 (showing biodegradability by means of biological treatment) and AOS and COS were increased to 2.26 and 3.08, respectively. Overall, the CWPO process with magnetite TNT/CNT nanocomposite, due to the simple and easy in-situ catalyst recovery/separation and good catalytic activity, can be considered as a promising destructive technology for industrial wastewater treatment.
Highlights
Polycarbonate plant wastewater (PCW) is typically characterized by high levels of aromatic hydrocarbons and phenolic substances, such as Bisphenol A, as well as high concentrations of salinity, inorganic dissolved salts and total dissolved solids (TDS) [1,2,3]
It can be concluded that the catalytic wet peroxide oxidation (CWPO) process using the magnetite titanium dioxide nanotubes (TNTs)/carbon nanotubes (CNTs) nanocomposite reveals high catalytic activity with complete Bisphenol A (BPA) degradation and 63% of total organic carbon (TOC) removal after 240 min of reaction time
The influence of operating parameters, including solution pH, H2O2 dosage, reaction temperature and catalyst loading was optimized in the CWPO process for degradation of BPA in the PCW
Summary
Polycarbonate plant wastewater (PCW) is typically characterized by high levels of aromatic hydrocarbons and phenolic substances, such as Bisphenol A, as well as high concentrations of salinity, inorganic dissolved salts and total dissolved solids (TDS) [1,2,3]. Bisphenol A (2, 2-bis (4-hydroxyphenyl) propane, BPA), characterized by two phenolic rings joined together through isopropylidene as bridging group, is a main industrial chemical widely used in plastic industry as intermediate in the manufacturing of polycarbonate and in the production of epoxy resins and corrosion-resistant unsaturated polystyrene resins [4,5]. BPA is classified as “moderately toxic” to aquatic organisms and considered an endocrine disrupting chemical (EDC) because of the similar structure with the estrogen receptors. Bearing this in mind, some studies reported that owing to its tumor promoting properties, BPA may be reasonably anticipated to be a human carcinogen [5,6,9,10]
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