Organic Compounds In Industrial Wastewater Research Articles

Heterogeneous Catalytic and Non-Catalytic Supercritical Water Oxidation of Organic Pollutants in Industrial Wastewaters Effect of Operational Parameters

This work reports supercritical water oxidation (SCWO) of organic pollutants in industrial wastewater in the absence and presence of catalysts. To increase the efficiency of the oxidation process, the SCWO of organic compounds in industrial wastewater was performed in the presence of various iron- and manganese-containing heterogeneous catalysts (Fe-Ac, Fe-OH, and Mn-Al). The catalytic and non-catalytic SCWO of organic compounds in wastewater from PJSC “Nizhnekamskneftekhim”, generated from the epoxidation of propylene with ethylbenzene hydroperoxide in the process of producing propylene oxide and styrene (PO/SM), was performed. The effect of operational parameters (temperature, pressure, residence time, type of catalysts, oxygen excess ratio, etc.) on the efficiency of the process of oxidation of organic compounds in the wastewater was studied. SCWO was studied in a flow reactor with induction heating under different temperatures (between 673.15 and 873.15 K) and at a pressure of 22.5 MPa. The reaction time ranged from 1.8 to 4.83 min. Compressed air was used as an oxidizing agent (oxidant) with an oxidant ratio of two to four. A pseudo-first-order model expressed the kinetics of the SCWO processes, and the rate constants were evaluated. In the present work, in order to optimize the operation parameters of the SCWO process, we used the thermodynamic properties of near- and supercritical water by taking into account the asymmetric behavior of the liquid–vapor coexistence curve.

Recent Advances in the Development of Novel Iron–Copper Bimetallic Photo Fenton Catalysts

Advanced oxidation processes (AOPs) have been postulated as viable, innovative, and efficient technologies for the removal of pollutants from water bodies. Among AOPs, photo-Fenton processes have been shown to be effective for the degradation of various types of organic compounds in industrial wastewater. Monometallic iron catalysts are limited in practical applications due to their low catalytic activity, poor stability, and recyclability. On the other hand, the development of catalysts based on copper oxides has become a current research topic due to their advantages such as strong light absorption, high mobility of charge carriers, low environmental toxicity, long-term stability, and low production cost. For these reasons, great efforts have been made to improve the practical applications of heterogeneous catalysts, and the bimetallic iron–copper materials have become a focus of research. In this context, this review focuses on the compilation of the most relevant studies on the recent progress in the application of bimetallic iron–copper materials in heterogeneous photo–Fenton-like reactions for the degradation of pollutants in wastewater. Special attention is paid to the removal efficiencies obtained and the reaction mechanisms involved in the photo–Fenton treatments with the different catalysts.

Janus mesoporous wood-based membrane for simultaneous oil/water separation, aromatic dyes removal, and seawater desalination

Directional transport of liquid is crucial for many applications including seawater desalination , oil/water separation, fog collection, membrane distillation and so forth. Particularly, Janus wood membranes, with asymmetric special wetting property on two sides, and mechanically robust bio-based substrate with ample pores and open nano-/micro-channels, present enticing opportunities to address this challenge. In this study, we report a Janus mesoporous wood-based membrane demonstrating the capabilities for simultaneous oil/water separation, aromatic dyes removal, and seawater desalination. Thanks to the inner driving force arising from the asymmetric special wettability, unique wood microchannels for the transpiration of trees, and the synergistic effect of PPy and Ag/AgCl NPs anchored to wood matrix, Janus mesoporous wood-based membrane would promote the desired transport without any external energy input for high-efficiency seawater desalination and switchable oil/water separation. Meanwhile, the aromatic dyes and other organic compounds in industrial wastewater or polluted seawater would get more opportunities to contact with the anchored Ag/AgCl NPs during flowing through the wood microchannels. Above advantages endow the Janus mesoporous wood-based membrane with excellent pollutant degradation efficiency (MB: 86.4 %, RhB: 91.9 %), high solar conversion efficiency (95.33 %), outstanding separation efficiency towards oil-in-water emulsion (∼99.51 %), remarkable oil adsorption capacity (∼8 times of its own weight), and great antibacterial efficiencies (E. coli: 99.87 %, S. aureus: 99.78 %, B. subtilis: 99.96 %). Results also show that this Janus mesoporous wood-based membrane has the satisfactory resistance to acid and base, robust mechanical structure, good recycling stability, high salinity tolerance and remarkable self-desalting capability. This study represents a new avenue for fabrication and design of Janus wood-based photothermal materials, and certainly will contribute to alleviating the global water and energy shortage issue. Asymmetric special wettability, unique wood microchannels, and the synergistic effect of PPy and Ag/AgCl NPs anchored to wood matrix endow the as-presented Janus mesoporous wood-based membrane with excellent aromatic dyes degradation efficiency (MB-86.4 %, RhB-91.9 %), high solar conversion efficiency (95.33 %), outstanding separation efficiency towards O/W emulsion (∼99.51 %), remarkable oil adsorption capacity (∼8 times of its own weight), great antibacterial efficiencies (E. coli-99.87 %, S. aureus-99.78 %, B. subtilis-99.96 %), and remarkable salinity tolerance. It certainly will contribute to alleviating the global water and energy shortage issue. • Mechanically robust wood membrane with asymmetric special wettability, ample pores and open microchannels was fabricated. • Janus wood membrane can simultaneously complete oil/water separation, aromatic dyes removal, and seawater desalination. • PPy/Ag/AgCl NPs endow the wood with excellent MB/RhB degradation efficiency, and high solar conversion efficiency (95.33 %). • It has oil/water separation efficiency (99.51 %), oil adsorption capacity (∼8 times), and antibacterial efficiency (99.96 %). • Such Janus mesoporous wood-based membrane will contribute to alleviating the global water and energy shortage issue.

Mechanisms associated with the separation of phenols from complex coexisting systems

Phenols are recognized as one of the major hazardous organic compounds in industrial wastewater. However, the effects of the coexisting substances on the elimination of the phenolic pollutants were less explored. Herein, we have systematically evaluated the adsorption processes of hydroquinone with respect to three adsorbents in acid, salt, and homolog systems. Our results demonstrated that low concentrations of coexisting acids could benefit the adsorption process with a maximum promotion rate of 143.4% (Qe from 74.3 to 180.9 mg/g), while high concentration of lactic acid resulted in considerable inhibition to St-DVB-nitro with a maximum inhibitory rate to 72.8% (Qe=20.2 mg/g). The coexisting salts exhibited a potentiation effect with a maximum promotion efficiency of 105.9% (Qe=153.0 mg/g). Competitive binding to adsorption sites could be observed in homolog coexisting system, where p-nitrophenol served as the dominant adsorbent and the hydroquinone adsorption capacity were only maintained at 45.4% (Qe=33.7 mg/g). On basis of the coexisting and preloading systems study, KCl could increase the force of mass transfer by salting-out effect and cation synergistic effect to promote the adsorption. Meanwhile, preloading experiments confirmed the competitive occupation effect of lactic acid and p-nitrophenol on the adsorption site, and the more hydrophobic p-nitrophenol could even desorbed hydroquinone (desorption rate 19.5–22.2%). This work on the interactions among phenols, coexisting factors and solid interfaces will guide the actual phenols wastewater treatment.

Enhancing electronic metal support interaction (EMSI) over Pt/TiO2 for efficient catalytic wet air oxidation of phenol in wastewater

Phenol is one of the major hazardous organic compounds in industrial wastewater. In this work, a highly active Pt/TiO2 catalyst for catalytic wet air oxidation (CWAO) of phenol was obtained by supporting pre-synthesized Pt on TiO2. During the followed hydrogen reduction, strong hydrogen spillover occurred without the migration of TiO2 onto Pt. The reduced support then enhanced the electron transfer from TiO2 to Pt, increasing the percentage of partially negative Pt (Ptδ-), which has been confirmed by XPS. The strong EMSI made the obtained catalyst far more active than Pt/TiO2 prepared by impregnation method. The electron-enriched Pt/TiO2 achieved total organic carbon (TOC) conversion of 88.8% and TOF 149 h−1 at 100 °C and 2 MPa O2, while conventional Pt/TiO2 gave TOC conversion of 39.5% and TOF 41 h−1 for CWAO of phenol. Our work indicates that the enhancement of EMSI between metal and support can be an effective approach to develop highly active catalysts for phenol treatment.

Application of a Solid Ceramic Membrane for Monitoring Volatile Organic Compounds in Industrial Wastewater.

A large quantity of volatile organic compounds (VOCs) can be released into water environments from oil spills and chemical exposure accidents. A recently developed solid ceramic dosimeter (SCD) could be used for long-term measuring of low VOCs concentrations in water. However, calibration and field testing of these SCDs have thus been far insufficient to apply for VOCs monitoring in a water environment in a chemical industrial area. We conducted laboratory calibration experiments and stability tests of the SCD. The mass accumulation of 14 target VOCs from 2 to 100 μg/L was increased linearly with time in the sampler. The absorption rate of the VOCs was related to Henry’s law constant. The average diffusion coefficient of the 14 VOCs in the SCD wall was 1.02 × 10−9 m2/s. The SCD was utilized in a petrochemical plant complex in South Korea with an industrial wastewater reservoir. After a total of 7 days of deployment, chloroform, ethylbenzene, and toluene were detected by both passive sampling and grab sampling at the same VOC concentrations.

Identification of unknowns in industrial wastewater using offline 2D chromatography and non-target screening

Industrial wastewater is characterised by a complex composition of trace organic compounds (TrOC) in a difficult matrix. The identification of unknown pollutants is of high interest. On the one hand to ensure protection of the environment by elucidating contaminations and on the other hand to protect the biological treatment step in the wastewater treatment plant (WWTP). Due to the high variability of the matrix, the identification of compounds of interest is very time consuming and often unsuccessful. To overcome this limitation, a prioritisation method was developed to identify so called ‘known unknowns’, i.e. compounds frequently detected but not identified, as prioritised compounds in industrial wastewater. The method based on an offline two-dimensional (offline 2D) liquid chromatography (LC) approach with ultra violet (UV) detection in the first and high-resolution mass spectrometry (HRMS) in the second dimension. As a proof of concept, an identification process of one ‘known unknown’ is described. The compound was identified as a dichlorodinitrophenol isomer by retention time in two dimensions, UV spectrum, exact mass, mass fragmentation and 1H- NMR. As prioritisation method, the offline 2D LC in combination with non-target analysis provides a powerful workflow to determine tentative structures of unknown organic compounds in industrial wastewater.

Combined homogeneous and heterogeneous advanced oxidation process for the treatment of tannery wastewaters

This study investigated the practical application of combined advanced oxidation processes (AOPs), such as homogeneous TiO2 photocatalysis and heterogeneous photo-Fenton, for the treatment of tannery wastewaters. An optimization study was conducted on the photocatalytic degradation of tannery wastewaters, in order to understand the effects of different operating parameters on the degradation kinetics. The chemical oxygen demand of tannery wastewater decreased from an initial level of 3,400 mg/L in raw wastewater to 140 mg/L (96% removal) in wastewater treated by the combined advanced oxidation process at optimum pH 7, TiO2 dosage of 0.2 g/L, Fe2+ dosage of 0.5 g/L, H2O2 dosage of 1.8 g/L and a treatment time of 4 hours. The biodegradability of wastewater increased from an initial level of 0.4 to 0.7 after treatment under optimum experimental conditions at a treatment time of 60 min. An annual treatment cost of US$21.34/m3 of treated water was obtained. The combined advanced oxidation process proved to be an efficient and appropriate technique for the effective removal of complex organic compounds in industrial wastewater.

Selective Adsorption of Naphthalene in Aqueous Solution on Mesoporous Carbon Functionalized by Task-specific Ionic Liquid

As a large group of persistent organic pollutants, polycyclic aromatic hydrocarbons (PAHs) commonly coexist with chlorinated organic compounds in industrial wastewater. Preferential adsorption of PAHs from wastewater and final effluent is essential in pretreatment processes. In this study, a novel nitrogen-doped mesoporous carbon (NMC) with high surface area (2130 m2/g) and bimodal pore size distribution (∼2 and ∼9.4 nm) was synthesized via a solvent evaporation induced self-assembly process using task-specific ionic liquid (TSIL) as the nitrogen source. The selective adsorption of naphthalene (NAP) with pentachlorophenol (PCP) on NMC in aqueous solution was investigated compared with conventional ordered mesoporous carbon (OMC). Kinetic studies revealed that the NAP adsorption process achieved equilibrium within 5 min and followed a pseudo-second-order rate equation. The adsorption capacity of NMC for NAP was 3.2 mmol/g, which was about 13 times that for PCP at pH 10 in a bi-solute system. The equilibriu...

Photocatalytic Oxidation of Phenolic Pollutants and Hydrophobic Organic Compounds in Industrial Wastewater Using Modified Nonosize Titanium Silicate-1 Thin Film Technology

Nanocrystalline Titanium Silicate-1 (TS-1) with attractive physical and chemical properties is being explored for the degradation of phenol. A fully dispersible nanocrystalline zeolite TS-1 was prepared. The catalyst was characterized by DLS, XRD, TEM and BET analyses. XRD analysis confirmed that the diffraction pattern of the NPs (CP-0) was very similar to that of amorphous silica and the aged concentrated precursor sample CP-48 showed peaks characteristic of MFI. TEM analysis confirmed that the size of the crystal is about 30 nm. The photocatalytic oxidation of phenol was studied over nanocrystalline Titanium silicate-1 thin film flow reactor. The experimental parameters such as aeration, flow rate, solution pH and phenol concentration were optimized. The degradation efficiency of choro-substituted phenols are compared at optimum conditions. In addition, photocatalytic degradation efficiency of simulated phenolic waste water was studied. The results are significant, as the method adopted here can be extended for the treatment and purification of waste water and air using nanocrystalline Titanium silicate-1 thin film flow reactor.

Iron Doped TiO<sub>2</sub> Photocatalysts for Environmental Applications: Fundamentals and Progress

One of the most pervasive problems affecting people throughout the world is inadequate access to clean water and sanitation. Problems with water are expected to grow worse in the coming decades, with water scarcity occurring globally. Many recent studies have been reported on the photodegradation of the organic compounds in industrial wastewater in the presence of TiO2 semiconductor as photocatalyst. Heterogeneous photocatalysts using iron as a dopant metal, so far, have been reported for various environmental applications. This paper highlights the recent advances and applications of Fe-TiO2 photocatalysis for the degradation/photodegradation of various pollutants, alkanolamines and other organic pollutants like phenols and dyes.

A combined electrocoagulation–electrooxidation treatment for industrial wastewater

This study addresses the elimination of persistent organic compounds in industrial wastewater using a synergistic combination of electrocoagulation and electrooxidation. Electrocoagulation is a relatively quick process (30 min), which is very effective in removing colloidal and suspended particles, as seen in changes in coliforms, turbidity, and color and in the general absorbance by UV–vis spectroscopy. However, it is relatively ineffective in eliminating stable persistent organic compounds—in this work, only half of the COD was eliminated from wastewater and an oxidation peak in the cyclic voltammetry scan remained. Electrooxidation is very effective in breaking down organic compounds through oxidation as reflected in the elimination of COD, BOD 5, and oxidative peak in cyclic voltammetry, but requires so much time (21 h) that it has very limited practicality, especially when colloidal and suspended particles are present. Electrooxidative mineralization of electrocoagulated wastewater, in which most of the colloids and charged species have been removed, takes less than 2 h. In the coupled technique, electrocoagulation quickly coagulates and removes the colloidal and suspended particles, as well as many charged species, then electrooxidation oxidizes the remaining organics. The coupled process eliminates COD, BOD 5, color, turbidity, and coliforms in a practical amount of time (2 h).

Using Oily Wastewater Emulsified Fuel in Boiler: Energy Saving and Reduction of Air Pollutant Emissions

The limited data for using emulsified oil have demonstrated its effectiveness in reducing flue gas pollutant emissions. The presence of a high concentration of toxic organic compounds in industrial wastewaters always presents significant problems. Therefore, this study was undertaken by using wastewater with COD of 9600 mg/L and total petroleum hydrocarbons-gasoline 440 mg/L for making an emulsified oil (wastewater content 20% with 0.1% surfactant) to evaluate the extent of reductions in both criteria pollutants and polycyclic aromatic hydrocarbons. For comparison, two other systems (heavy oil fuel and water-emulsified oil) were also conducted. The wastewater-emulsified oil fuel results in significant reductions in particulate matter (PM), NO(x), SO2, and CO as compared to heavy oil fuel and similar to those from water/oil emulsified fuel; for PM, it is better in wastewater-emulsified oil. The reductions of total PAH flue gas emissions are 38 and 30% for wastewater- and water-emulsified fuel, respectively; they are 63 and 44% for total BaP(eq), respectively. In addition to reducing flue gas pollutant emissions, the results also demonstrate that the use of wastewater-emulsified fuel in boiler operation provides several advantages: (1) safe disposal of industrial wastewater; and (2) energy savings of about 13%. Thus, wastewater/oil-emulsified fuel is highly suitable for use in boilers.

Polycyclic aromatic hydrocarbons (PAHs), organic matter quality and meiofauna in Galician sandy beaches, 6 months after the Prestige oil-spill

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Kinetics and toxicity of direct reaction between ozone and 1,2-dihydrobenzene in dilute aqueous solution

The presence of toxic aromatic organic compounds in industrial wastewater affects the efficiency of conventional biological treatment. The oxidizing power of ozone represents an interesting pretreatment to reduce toxicity and increase biodegradability. At low pH, ozone is known to attack electron-rich structures by direct electrophilic reactions which open aromatic rings, and generate smaller oxidized compounds. This paper reports experimental results on kinetic and toxicity aspects of ozone direct reactions with 1,2-dihydrobenzene. This toxic compound is frequently found in cellulose bleaching effluents. Although the reaction pathway is rather complex, 4-carbon compounds, such as maleic acid, are readily formed during the first stage of ozonation. These 4-carbon compounds are further oxidized to form smaller molecules (mostly 2-carbon, such as oxalic acid). The apparent kinetics of 1,2-dihydrobenzene follows a second order law, with a rate constant around 0.36 (dm3 mmol-1s-1), at pH 2 and 20 degrees C. Results show that the BOD:COD ratio increase five-fold as ozonation progresses. Furthermore, the mutagenicity of 1,2-dihydrobenzene totally disappears as the aromatic compound is destroyed by ozonation.

Lumped kinetic model for catalytic wet oxidation of organic compounds in industrial wastewater

AbstractA simplified reaction pathway was proposed to describe the kinetic behavior of catalytic wet oxidation of organic mixture. The oxidation reactions were divided and lumped into two groups: (1) the deep or complete oxidation reactions with formation of CO2 and H2O; (2) the partial oxidation reactions with formation of all intermediates in aqueous solution of the industrial wastewater. The concentrations of all reactants in wastewater and those of the intermediates formed during the reaction are also represented by a lumped concentration of total organic carbon (TOC). To test the model, catalytic oxidation of organic pollutants in an effluent from a softwood Kraft pulp mill was investigated in a slurry reactor using a Pd‐Pt/Al2O3 catalyst. Sodium hydroxide was used to adjust the initial pH of wastewater to 7.3 to avoid the problem of metal leaching and excessive corrosion. The lumped kinetic model developed in this study describes well both our experimental data and those reported in literature. The lumped kinetic model proposed in this study can be used for both catalytic and noncatalytic wet oxidation processes.

Toxicity-directed fractionation of organic compounds in tannery wastewater with regard to their molecular weight and polarity

A toxicity-directed fractionation scheme for organic compounds in industrial wastewaters is presented. The sequential application of the three separation methods (ultrafiltration, preparative gel permeation chromatography, and solid-phase extraction) allows the separation of wastewater constituents with regard to their molecular weight and their polarity. After each separation step the dissolved organic carbon (DOC) and the luminescence inhibition of the fractions are measured. With this information the nature of the inhibiting substances in a wastewater sample can be characterized. Additionally, the fractions which show increased toxic effects can undergo further testing for identification of the responsible compounds. An untreated and biologically treated (anaerobic and anaerobic/aerobic) tannery wastewater were used for the development of the fractionation scheme.