Catalytic thermolysis in treating Cibacron Blue in aqueous solution: Kinetics and degradation pathway

Intermolecular degradation of aromatic compound and its derivatives via combined sequential and hybridized process

The under-treated wastewater, especially remaining carcinogenic aromatic compounds in wastewater discharge has been expansively reported, wherein the efficiency of conventional wastewater treatment is identified as the primary contributor source. Herein, the advancement of wastewater treatments has drawn much attention in recent years. In the current study, combined sequential and hybridized treatment of thermolysis and coagulation-flocculation provides a novel advancement for environmental emerging pollutant (EP) prescription. This research is mainly demonstrating the mitigation efficiency and degradation pathway of pararosaniline (PRA) hybridized and combined sequential wastewater treatment. Notably, PRA degradation dominantly via a linkage of reaction: thermal cleavage, deamination, silication and diazene reduction. Thermolysis acts as an initiator for the PRA decomposition through thermally induced bond dissociation energy (BDE) for molecular fragmentation whilst coagulation-flocculation facilitates the formation of organo-bridged silsesquioxane as the final degradation product. Different from conventional treatment, the hybridized treatment showed excellent synergistic degradability by removing 99% PRA and its EPs, followed by combined sequential treatment method with 86% reduction. Comprehensive degradation pathway breakdown of carcinogenic and hardly degradable aromatic compounds provides a new insight for wastewater treatment whereby aniline and benzene are entirely undetectable in effluent. The degradation intermediates, reaction derivatives and end products were affirmed by gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy and ultraviolet-visible spectrophotometry (GC-MS, FTIR and UV-Vis). This finding provides valuable guidance in establishing efficient integrated multiple-step wastewater treatments.

Catalytic thermolysis treatment of petroleum refinery wastewater collected from effluent treatment plant

Catalytic thermolysis of petroleum refinery wastewater was investigated as a pretreatment process. Effects of various parameters like temperature, pH, dose of catalyst and time were investigated for chemical oxygen demand (COD), turbidity, and element reduction. CuSO4, FeSO4, FeCl3, and 1:1 ratio (v:v) mixture of CuSO4 and FeCl3 were used as a catalyst. The maximum reduction of COD and turbidity were 90 and 98% by mixture (1:1) of CuSO4 and FeCl3 at 70 °C, 7 pH, 1.0 kg/m3 dose in 90 min reaction time. The removal of an element like Cr, Mn, Ni, and Pb was analyzed by ICP-OES. The sludge precipitated after catalytic thermolysis was characterized using scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), Fourier transform infrared (FTIR) and thermo-gravimetric analysis (TGA)/derivative thermal analysis (DTA) analyses. Sludge from CuSO4 and mixture of CuSO4 and FeCl3 treatment has a compact structure with irregular granule which favors adsorption.

Degradation reaction of Diazo reactive black 5 dye with copper (II) sulfate catalyst in thermolysis treatment

The theme of present research demonstrates performance of copper (II) sulfate (CuSO₄) as catalyst in thermolysis process to treat reactive black 5 (RB 5) dye. During thermolysis without presence of catalyst, heat was converted to thermal energy to break the enthalpy of chemical structure bonding and only 31.62% of color removal. With CuSO₄ support as auxiliary agent, the thermally cleaved molecular structure was further destabilized and reacted with CuSO₄. Copper ions functioned to delocalize the coordination of π of the lone paired electron in azo bond, C=C bond of the sp² carbon to form C-C of the sp³ amorphous carbon in benzene and naphthalene. Further, the radicals of unpaired electrons were stabilized and RB 5 was thermally decomposed to methyl group. Zeta potential measurement was carried out to analyze the mechanism of RB 5 degradation and measurement at 0 mV verified the critical chemical concentration (CCC) (0.7 g/L copper (II) sulfate), as the maximum 92.30% color removal. The presence of copper (II) sulfate catalyst has remarkably increase the RB 5 dye degradation as the degradation rate constant without catalyst, k₁ is 6.5224 whereas the degradation rate constant with catalyst, k₂ is 25.6810. This revealed the correlation of conversion of thermal energy from heat to break the chemical bond strength, subsequent fragmentation of RB 5 dye molecular mediated by copper (II) sulfate catalyst. The novel framework on thermolysis degradation of molecular structure of RB 5 with respect to the bond enthalpy and interfacial intermediates decomposition with catalyst reaction were determined.