Photolysis, sonolysis, and photosonolysis of common groundwater contaminants, namely 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene, were investigated using a flow-through photosono reactor system. Simulated groundwater containing the chlorinated volatile organic compounds (VOCs) was exposed to ultraviolet light (UV), ultrasonication (US), and UV and US concurrently (UVUS), without a photo catalyst. VOC removal efficiencies of the UV, US, and UVUS treatment processes were computed from the VOC concentrations in influent and effluent of the reactor. The process using UVUS exhibited larger degradation efficiencies than that with UV and US separately in most cases; however, statistical analysis showed that the UVUS treatment efficiency is likely to be additive of the UV and US treatment efficiencies. The results also showed that the increase of the detention time from 26 to 60 min had no significant effect on the VOC removal efficiencies in these processes.

In this study, the photocatalytic degradation of commercial azo dye (Remazol Red 133) in the presence of titanium dioxide (TiO2) suspensions as photocatalyst was investigated. The effect of various operational parameters, such as pH of dye solution and catalyst concentration on the photocatalytic degradation process, was examined. The mineralization of dye was also evaluated by measuring the chemical oxygen demand of the dye solutions. The extent of photocatalytic degradation was found to increase with increasing TiO2 concentration. For the Remazol Red dye solutions, a 120-min treatment resulted in 97.9% decolorization and 87.6% degradation at catalyst loading of 3 g/L. Experiments using real textile wastewater were also carried out. Textile wastewater degradation was enhanced at acidic conditions. The decolorization and degradation efficiencies for textile wastewater were 97.8% and 84.9% at pH 3.0, catalyst loading of 3 g/L, and treatment time of 120 min.

Fluid catalytic cracking of heavy ends to high-value liquid fuels is a common unit operation in oil refineries. In this process, the heavy feedstock that contains sulfur is cracked to light products. Sulphur content is hence redistributed in the liquid and gaseous products and coke of the catalyst used in this process. The coke is later burnt in the regenerator releasing sulfur into the discharged flue gas as SO₂. In the present work, comprehensive emission inventories for a fluid catalytic cracking unit in a typical oil refinery are prepared. These inventories are based on calculations that assume complete combustion of catalyst coke in the regenerator. Yearly, material balances for both SO₂ and particulate matters emissions are carried out taking into account seasonal variations in the operation of the process unit. The results presented in this article reflect the variation of sulfur in feedstock originating from various units in the refinery. The refinery operations are not dependant on seasons but controlled by market-driven conditions to maximize the profit. The seasonal impact on refinery emissions is minimal due to its operation at optimum capacity fulfilling the international market demand. The data presented and analyzed here can be used to assess the hazardous impact of SO₂ and particulate matter emissions on surrounding areas of the refinery.

The heterogeneous photocatalytic water purification process has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible light spectrum. This paper aims to review and summarize the recently published works in the field of photocatalytic oxidation of toxic organic compounds such as phenols and dyes, predominant in wastewater effluent. In this review, the effects of various operating parameters on the photocatalytic degradation of phenols and dyes are presented. Recent findings suggested that different parameters, such as type of photocatalyst and composition, light intensity, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, oxidizing agents/electron acceptors, mode of catalyst application, and calcinations temperature can play an important role on the photocatalytic degradation of organic compounds in water environment. Extensive research has focused on the enhancement of photocatalysis by modification of TiO2 employing metal, non-metal, and ion doping. Recent advances in TiO2 photocatalysis for the degradation of various phenols and dyes are also highlighted in this review.

Photocatalytic degradation of bisphenol A (2,2-bis(4-hydroxyphenyl)propane, BPA), a representative endocrine-disrupting compound, was carried out in the presence of the Ti-MCM-41 mesoporous molecular sieve in this investigation. The degradation rate was strongly dependent on those factors such as the catalyst, catalyst amount, radiation time, and pH value. The photolysis reaction was found to follow the Langmuir-Hinshelwood model. After the photocatalytic treatment, decomposition of BPA rendered five intermediates as follows: 2-methyl-2,3-dihydrobenzofuran, 4-hydroxyacetophenone, 1,1-diethoxyethane, isobutanol, and 3-methylbutanal, which could be the direct evidence supporting our proposal for the degradation mechanism.

Fluid catalytic cracking unit is of great importance in petroleum refining industries as it treats heavy fractions from various process units to produce light ends (valuable products). FCC unit feedstock consists of heavy hydrocarbon with high sulfur contents, and the catalyst in use is zeolite impregnated with rare earth metals, i.e., lanthanum and cerium. Catalytic cracking reaction takes place at elevated temperature in fluidized bed reactor generating sulfur-contaminated coke on the catalyst with large quantity of attrited catalyst fines. In the regenerator, coke is completely burnt producing SO2, PM emissions. The impact of the FCC unit is assessed in the immediate neighborhood of the refinery. Year-long emission inventories for both SO2 and PM have been prepared for one of the major petroleum refining industry in Kuwait. The corresponding comprehensive meteorological data are obtained and preprocessed using Aermet (Aermod preprocessor). US EPA approved dispersion model, Aermod, is used to predict ground level concentrations of both pollutants in the selected study area. Model output is validated with measured values at discrete receptors, and an extensive parametric study has been conducted using three scenarios, stack diameter, stack height, and emission rate. It is noticed that stack diameter has no effect on ground level concentration, as stack exit velocity is a function of stack diameter. With the increase in stack height, the predicted concentrations decrease showing an inverse relation. The influence of the emission rate is linearly related to the computed ground level concentrations.

In the last 10 years, the number of field applications of zero-valent iron differing from permeable reactive barrier has grown rapidly and at present are 112. This study analyzes and compares such field applications. By using statistical analysis, especially ANOVA and principal component analysis, this study shows that chlorinated solvent contamination can be treated efficiently by using zero-valent iron material singly or associated with other technologies. In the analyzed sample of case studies, the association with microbial dechlorination increased significantly the performances of nanoscale iron. This is likely due to the synergistic effect between the two processes. Millimetric iron was always used in association with source zone containment; therefore, it is not possible to distinguish the contributions of the two techniques. The comparison also shows that catalyst addition seems to not dramatically improve treatment efficiency and that such improvement is not statistically significant. Finally, the injection technology is correlated to the type of iron and to the soil permeability.

BACKGROUND, AIM, AND SCOPE: Textile industry produces wastewater which contributes to water pollution since it utilizes a lot of chemicals. Preliminary studies show that the wastewater from textile industries contains grease, wax, surfactant, and dyes. The objective of this study was to determine the treatment efficiency of the nickel catalysts supported on hydrotalcites in three-dye model compounds and two types of wastewater. MATERIALS AND METHODS: Hydrotalcites were employed to prepare supported nickel catalysts by wetness impregnation technique. Metal loadings from 1 to 10 wt% were tested. Catalysts were characterized by several techniques. They were tested in a catalytic wet air oxidation of three dyes and two wastewaters with different origins. RESULTS AND DISCUSSION: It could be observed that the higher the metal content, the lower the BET area, possibly due to sintering of Ni and the consequent blocking of the pores by the metal. In addition, metallic dispersion was also higher when the metal content was lower. Dye conversion was more than 95% for every catalyst showing no differences with the nickel content. A high degree of dye conversion was achieved. Wet air oxidation (WAO) and catalytic wet air oxidation (CWAO) processes have been proved to be extremely efficient in TOC removal for wastewaters. CONCLUSIONS: The CWAO process can be used to remove dyes from wastewater. Three different dyes were tested showing satisfactory results in all of them. TOC degradation and dye removal in the presence of the catalyst were effective. Also, the HTNi catalyst is very active for organic matter and toxicity removal in wastewaters.