Application of photocatalytic proxone process for petrochemical wastewater treatment.

Industrial wastewaters are different from sanitary wastewaters, and treatment complications due to their unique characteristics, so biological processes are typically disrupted. High chemical oxygen demand, dye, heavy metals, toxic organic and non-biodegradable compounds present in petroleum industry wastewater. This study intends to optimize the photocatalytic proxone process, utilizing a synthesized ZnO-Fe3O4 nanocatalyst, for petroleum wastewater treatment. The synthesis of ZnO-Fe3O4 was done by air oxidation and layer-by-layer self-assembly method and XRD, SEM, EDAX, FT-IR, BET, DRS, and VSM techniques were used to characterize the catalyst. Central composite design (CCD) method applied to investigated the effect of pH (4-8), reaction time (30-60 min), ozone gas concentration (1-2 mg/L-min), hydrogen peroxide concentration (2-3 mL/L) and the amount of catalyst (1-0.5 g/L) on the process. In the optimal conditions, biological oxygen demand (BOD5) and total petroleum hydrocarbon (TPH) removal, reaction kinetic, and synergistic effect mechanisms on the process were studied. Based on the ANOVA, a quadratic model with R2 = 0.99, P-Value = 0.0001, and F-Value = 906.87 was proposed to model the process. Based on the model pH = 5.7, ozone concentration = 1.8 mg/L-min, hydrogen peroxide concentration = 2.5 mL/L, reaction time = 56 min, and the catalyst dose = 0.7 g/L were proposed as the optimum condition. According to the model prediction, an efficiency of 85.3% was predicted for the removal of COD. To evaluate the accuracy of the prediction, an experiment was carried out in optimal conditions, and experimentally, a 52% removal efficiency was obtained. Also, at the optimum condition, BOD5 and TPH removal were 91.1% and 89.7% respectively. The reaction kinetic follows the pseudo-first-order kinetic model (R2 = 0.98). Also, the results showed that there is a synergistic effect in this process. As an advanced hybrid oxidation process, the photocatalytic proxone process has the capacity to treat petroleum wastewater to an acceptable standard.

Rapid extraction of BTEX in water and milk samples based on functionalized multi-walled carbon nanotubes by dispersive homogenized-micro-solid phase extraction.

An advanced synthesis based on the phenylalanine (Phe) and task-specific ionic liquid (TSIL) functionalized on multi-walled carbon nanotubes (Phe/TSIL@MWCNTs), was used to extract benzene, ethylbenzene, toluene, and xylene (BTEX) from cow's milk, powdered milk, and farm water samples. The BTEX was efficiently extracted by ultrasound-assisted dispersive homogenized-micro-solid phase extraction (USA-DH-µ-SPE) between 95.1% and 103.4%. By procedure, 50 mg of Phe/TSIL@MWCNTs was added to 0.2 mL of acetone and injected into 10 mL of the samples. The upper aqueous solution was vacuumed, the vial heated to 80 °C, and the BTEX desorbed in the vial. Then, using a Hamilton syringe, 1-20 µL of gas in the headspace vial was determined by injecting it into the gas chromatography with flame ionization detection (GC-FID). The linear range, LOD, and LOQ for BTEX in milk and water samples were obtained at 0.05-500 µg L-1, 15 ng L-1, and 50 ng L-1, respectively (r = 0.9997, RSD% = 2.27).

An immobilization of aminopropyl trimethoxysilane-phenanthrene carbaldehyde on graphene oxide for toluene extraction and separation in water samples.

A new functionalized Nano graphene with aminopropyl trimethoxysilane-phenanthrene-4-carbaldehyde (NGO@APTMS-PNTCA) as a novel adsorbent was used to extract toluene from water samples by the ultrasound-assisted dispersive solid-phase microextraction procedure (USA-D-SPME). So, 50 mg of NGO@APTMS-PNTCA adsorbent was added to water samples and sonicated for 20 min. After toluene extraction, the NGO@APTMS-PNTCA adsorbent separated from the liquid phase with a Whatman membrane filter (200 nm). Then, the toluene was back-extracted from the adsorbent by 2.0 mL of the acetone/ethanol (1:1, eluent) at 25 °C. Due to the physical properties and structure of toluene, fluorobenzene was used as an internal standard. Finally, the toluene values were measured by a gas chromatography-flame ionization detector (GC-FID). In optimized conditions, the limit of detection (LOD), the working range (WR), and the enrichment factor (EF) were obtained at 2.5 µg L-1, 0.01-1.2 mg L-1, and 9.63, respectively (MRSD% = 3.38). Also, the limit of quantification (LOQ) 10 µg L-1 and extraction recovery of more than 95% was efficiently achieved for toluene. Standard additions of toluene to blank solutions had high recoveries between 95.2% and 104.5% with a relative standard deviation (RSD%) of 0.27-5.2. The absorption capacities of NGO and NGO@APTMS-PNTCA adsorbents for toluene extraction were obtained at 32.8 mg g-1 and 154.9 mg g-1, respectively. The USA-D-SPME method was validated by spiking the standard concentrations of toluene. The proposed method demonstrated relevant and suitable statistical results with high accuracy and precision for toluene extraction by a novel adsorbent synthesis.

Temperature-responsive graphene oxide/N-isopropylacrylamide/2-allylphenol nanocomposite for the removal of phenol and 2,4-dichlorophenol from aqueous solution.

In this study, a novel thermo-responsive polymer was synthesized with efficient grafting of N-isopropylacrylamide as a thermosensitive polymer onto the graphene oxide surface for the efficient removal of phenol and 2,4-dichlorophenol from aqueous solutions. The synthesized polymer was conjugated with 2-allylphenol. Phenol and 2,4-dichlorophenol were monitored by ultra-performance liquid chromatography system equipped with a photodiode array detector. The nanoadsorbent was characterized by different techniques. The nanoadsorbent revealed high adsorption capacity where the removal percentages of 91 and 99% were found under optimal conditions for phenol and 2,4-dichlorophenol, respectively (for phenol; adsorbent dosage = 0.005 g, pH = 8, temperature= 25 °C, contact time = 60 min; for 2,4-dichlorophenol; adsorbent dosage = 0.005 g, pH = 5, temperature = 25 °C, contact time = 10 min). Adsorption of phenol and 2,4-dichlorophenol onto nanoadsorbent followed pseudo-second-order kinetic and Langmuir isotherm models, respectively. The values of ΔG (average value = - 11.39 kJ mol-1 for phenol and 13.42 kJ mol-1 for 2,4-dichlorophenol), ΔH (- 431.72 J mol-1 for phenol and - 15,721.8 J mol-1 for 2,4-dichlorophenol), and ΔS (35.39 J mol-1 K-1 for phenol and - 7.40 J mol-1 K-1 for 2,4-dichlorophenol) confirmed spontaneous and exothermic adsorption. The reusability study indicated that the adsorbent can be reused in the wastewater treatment application. Thermosensitive nanoadsorbent could be used as a low-cost and efficient sorbent for phenol and 2,4-dichlorophenol removal from wastewater samples.

Electro dialysis reversal (EDR) performance for reject brine treatment of reverse osmosis desalination system.

In this study, the performance of bench-scale EDR was evaluated using the samples taken from the 1st and the 2nd stage RO from the Brackish Water Reverse Osmosis (BWRO) plant in Eshtehard, Iran. The measurements indicated that original TDS of the aquifer brackish water was equal to 3,229-3,664 mg/L, whereas TDS of the 1st stage RO brine was between 5,500 and 7,700 mg/L, that TDS of the 2nd stage RO brine was in the range of 9,500-10,600 mg/L. A batch bench-scale EDR system of 12 l/h was used with a direct electric current at three different scenarios. In the first, the brine was fed at 20°C (as a reference regulated point). In the second, temperature (14, 20, 26.5°C), and in the third, voltage were changed (6, 12, 18, 24 V) to investigate their influences on performance of the EDR process, while the other operational parameters (feed flow rate, recovery ratio, quality of feed brine)were kept constant. Based on the data analysis using the ANOVA and DUNCAN tests for the second and third scenarios, it was observed that the optimum TDS removal efficiency of the EDR process can be at temperature of 26.5°C and voltage of 18 V. On the other hand, the successful performance of the bench-scale EDR in reducing the 29,000 mg/L TDS and the 45,000 µmhos/cm EC of the 2nd stage brine to 1,716 mg/L (TDS) and 2,640 µmhos/cm (EC) (at 26.5°C and 24V) could be considered as the main achievement of this research. Overall, the hybrid process RO-EDR-RO can be considered as the best technical, environmental and economical scenario for the development of Eshtehard Desalination Plant phase 2 at full scale.

Effective leachate treatment by a pilot-scale submerged electro-membrane bioreactor.

Most landfill leachates contain organic compounds that cannot be easily separated by conventional biological processes. Recently, integration of membrane bioreactors and electro-oxidation has been proposed as a suitable option for the treatment and separation of organic and inorganic contaminants in leachate. Therefore, in the present study, the performance of submerged electro-membrane bioreactor (SEMBR) along with a conventional membrane bioreactor (MBR) on a pilot scale was evaluated for the treatment of leachate. Both bioreactors were used to compare treatment efficiency under the same conditions. The removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), phosphate (PO43--P), color, UV254, and metals were investigated. The results showed that applying electric current to the MBR could approximately increase the COD removal efficiency from 94 to 98.5%; PO43--P removal from 70 to 99%; NH3+-N removal from 91 to 99%; UV254 removal from 80 to 96%; and heavy metals removal from 40 to 95%. Humic acid removal efficiency as another indicator of humic substances was increased from 75% in the MBR to 96% in the SEMBR process. The results also showed that the effluent can be introduced into the wastewater treatment plant for further treatment. The SEMBR process achieved a minimization of fouling of membranes compared to conventional MBR. The consumption of the energy and electrode was in accordance with the previous results, and the required energy of 1.57 kWh/m3 of wastewater was calculated. The sludge volume index (SVI) in SEMBR (105 ml/g) was better than MBR (135 ml/g) due to the electrokinetic effect on the production of denser flocs. Based on the results, it can be concluded that the application of electric current can improve the performance of MBR in removing PO43-, NH4+, and membrane fouling.

Comparing the performance of the conventional and fixed-bed membrane bioreactors for treating municipal wastewater.

Membrane bioreactor (MBR) is relatively a new technology in wastewater treatment. It can efficiently remove soluble and suspended organics. However, it may constantly encounter bio-fouling and cannot efficiently remove nutrient pollutants. These two deficiencies have motivated researchers to upgrade the design and operation of conventional MBR (CMBR). This study evaluates the performance of hybrid fixed bed MBR (FBMBR) treating real domestic wastewater in different operational conditions. It also compares the experimental results of FBMBR with the CMBR. For this purpose, two identical reactors are constructed as CMBR and FBMBR. Each module contains the net volume of 140 L and is operated continuously in two aerobic (DO > 4 mg/L) and anoxic (DO < 1 mg/L) conditions with average organic loading rates (OLRs) of 0.58, 0.71 and 1.55 kgCOD/m3d. The pore sizes of flat sheet membranes are 0.2-0.8 µm with total surface area of 1.4m2 per module. The experimental results revealed that the removal efficiencies of BOD, COD and TSS are above 95 % in both CMBR and FBMBR in all operating conditions. However, fouling occurs with lower rates in FBMBR. The growing rate of transmembrane pressure (TMP) in aerobic condition is 1.7mBar/day in CMBR, while it reduces to 1.2mBar/day for FBMBR in solid retention time (SRT) of 75 days and OLR of 0.58 and 0.71 kgCOD/m3d. In anoxic condition with SRT of 100 days and OLR of 1.55 kgCOD/m3d, the TMP in FBMBR is 59 % of CMBR. In addition, total nitrogen (TN) removal is between 12 % (aerobic) and 27 % (anoxic) in CMBR, while it is between 25 % (aerobic) and 49 % (anoxic) in FBMBR. Total phosphorous (TP) removal also ranges between 50 and 66 % in CMBR, while it is between 51 and 86 % in FBMBR. Consequently, using hybrid systems of FBMBR can reduce membrane fouling rate and improve nutrient removal efficiency in comparison with CMBR. This approach can reinforce the biological treatment efficiency and preserve permeate quality in higher OLRs or in lower DO level.

Process optimization and enhancement of pesticide adsorption by porous adsorbents by regression analysis and parametric modelling.

In the present study, the adsorptive removal of organophosphate diazinon pesticide using porous pumice adsorbent was experimentally investigated in a batch system, modelled and optimized upon response surface methodology (RSM) and artificial neural network-genetic algorithm (ANN-GA), fitted to isotherm, kinetic and thermodynamic models. The quantification of adsorbent elements was determined using EDX. XRD analysis was utilized to study the crystalline properties of adsorbent. The FT-IR spectra were taken from adsorbent before and after adsorption to study the presence and changes in functional groups. The constituted composition of the adsorbent was determined by XRF. Also, the ionic strength and adsorbent reusability were explored. The influences of operational parameters like pH, initial pesticide concentration, adsorbent dosage and contact time were investigated systematically. ANN-GA and RSM techniques were used to identify the optimal process variables that result in the highest removal. Based on the RSM approach, the optimization conditions for maximum removal efficiency is obtained at pH = 3, adsorbent dosage = 4 g/L, contact time = 30 min, and initial pesticide concentration = 6.2 mg/L. To accurately identify the parameters of nonlinear isotherm and kinetic models, a hybrid evolutionary differential evolution optimization (DEO) is applied. Results indicated that the equilibrium adsorption data were best fitted with Langmuir and Temkin isotherms and kinetic data were well described by pseudo-first and second-order kinetic models. The thermodynamic parameters such as entropy, enthalpy and Gibbs energy were evaluated to study the effect of temperature on pesticide adsorption.

Application of polyamide thin-film composite layered on polysulfone-GO/TiO2 mixed matrix membranes for removal of nitrotoluene derivatives from petrochemical wastewaters.

Release of harmful organic intermediates or byproducts during the manufacture of petrochemical compounds is a serious problem in petrochemical plants. In this work, polysulfone membranes blended with GO/TiO2 nanocomposite were synthesized by phase inversion method and coated with a polyamide layer formed by interfacial polymerization to prepare a thin-film composite (TFC) sample. Analysis and characterization of the sample were carried out by XRD, FE-SEM, BET, FTIR/ATR, AFM, TGA, and zeta potential. Results indicated that incorporation of GO/TiO2 into the membrane structure enhanced porosity, surface roughness, and macrovoid formation along the cross-section of the sublayer and permeability of the membrane. The TFC membranes were applied to remove mononitrotoluene (MNT) and dinitrotoluene (DNT) as the basic intermediates of toluene diisocyanate (TDI). The membranes demonstrated high efficiency (> 90%) for the removal of MNT and DNT according to the charge exclusion mechanism and Donnan effect. Application of the TFC membrane for treatment of wastewater in the TDI plant showed that the removal of pollutants is variable in the range of 45-65% and 53-69% for the membrane with the highest flux and highest rejection in different transmembrane pressure, respectively.

Simultaneous removal of a cationic and an anionic textile dye from water by a mixed sorbent of vermicompost and Persian charred dolomite.

The potential of a mixed sorbent consisting of vermicompost and Persian charred dolomite for simultaneous adsorption of Basic Violet 16 (BV16) and Reactive Red 195 (RR195) was investigated. First-order derivative spectrophotometry was used for simultaneous analysis of the two dyes. In single dye experiments, the maximum adsorption capacity of vermicompost for BV16 was found to be 16 mg g-1 and the adsorption capacity of charred dolomite for RR195 was 7.3 mg g-1. Anionic RR195 was not noticeably adsorbed by vermicompost (negative surface charge) and cationic BV16 not by charred dolomite (positive surface charge) but adsorbed by the oppositely charged adsorbents which indicates a selective electrostatic adsorption mechanism. In binary dye solution, BV16 adsorption onto charred dolomite was increased in the presence of RR195 (synergistic effect), yet RR195 adsorption on charred dolomite was not influenced by BV16. An antagonistic effect of RR195 was concluded for BV16 adsorption onto vermicompost. The adsorption equilibrium data for both adsorbents fitted more acceptable to the Langmuir isotherm model than to the Freundlich model in single and binary solutions, but other than the adsorption of BV16 on vermicompost in binary solution which followed the Freundlich model. More than 50% of the removal efficiencies determined for both dyes onto the mixed sorbents were >70% which highlights that the mixed sorbent investigated is highly efficacious for the simultaneous removal of cationic and anionic dyes from contaminated groundwater. Eight cycles reusing vermicompost with 1 N NaOH for regeneration demonstrates the practicability and economic advantage of this natural biosorbent.

Application of Cu/Mg/Al-chitosan-O3 system for landfill leachate treatment: Experimental and economic evaluation data.

Landfill leachate contains heavy organic pollutants, which pollute ground and surface waters. This dataset applied a newly-introduced catalyst, Cu/Mg/Al-chitosan, for a landfill leachate treatment during a catalytic oxidation. The data of chemical oxygen demand (COD) and colour removal from the leachate was reported as a function of reaction time (20-460 min). Economic evaluation data of the Cu/Mg/Al-chitosan-O3 system showed that the current cost of the system for treating each m3 leachate is US$ 18 and for catalyst synthesis is US$ 54.5. Data could be useful from environmental and economic perspectives to those concerned about landfill leachate threats.

Fractionation of heavy metals in bottom sediments in Chahnimeh 1, Zabol, Iran.

In the present study, 180 sediment samples were collected from the Chahnimeh 1 reservoir to investigate the concentration of metal and sequential extraction. Five geochemical phases (exchangeable fraction, carbonate fraction, Fe/Mn oxide fraction, organic fraction and residual fraction) for the determination of the speciation of heavy metals (Zn, Fe, Cd, Pb, Mn, Ni) as proposed by Tessier was applied to sediments collected from Chahnimeh 1. Results were obtained for nickel and cadmium, as over 40 % of metal was present in the exchangeable phase and bound to carbonate. According to the risk assessment code (RAC), sediments that have 31 to 50 % carbonate and exchangeable fraction are high risk. Similar results were obtained for zinc and lead. The major fraction of the two metals (63 % of the total concentration for lead and 85 % of the total concentration for zinc) occurred in the residual phase and fraction-bound hydrous Fe-Mn oxides. The risk assessment showed moderate risk for lead and no risk for zinc. This indicates that the Igeo and IPOLL used in the present investigation showed no pollution to moderate pollution in terms of metals in sediments.

Utilization of moving bed biofilm reactor for industrial wastewater treatment containing ethylene glycol: kinetic and performance study.

One of the requirements for environmental engineering, which is currently being considered, is the removal of ethylene glycol (EG) as a hazardous environmental pollutant from industrial wastewater. Therefore, in a recent study, a moving bed biofilm reactor (MBBR) was applied at pilot scale to treat industrial effluents containing different concentrations of EG (600, 800, 1200, and 1800 mg L-1 ). The removal efficiency and kinetic analysis of the system were examined at different hydraulic retention times of 6, 8, 10, and 12 h as well as influent chemical oxygen demand (COD) ranged between values of 1000 and 3000mg L-1. In minimum and maximum COD Loadings, the MBBR showed 95.1% and 60.7% removal efficiencies, while 95.9% and 66.2% EG removal efficiencies were achieved in the lowest and highest EG concentrations. The results of the reactor modelling suggested compliance of the well-known modified Stover-Kincannon model with the system.

Efficient biodegradation of naphthalene by a newly characterized indigenous Achromobacter sp. FBHYA2 isolated from Tehran Oil Refinery Complex.

A bacterial strain, FBHYA2, capable of degrading naphthalene, was isolated from the American Petroleum Institute (API) separator of the Tehran Oil Refinery Complex (TORC). Strain FBHYA2 was identified as Achromobacter sp. based on physiological and biochemical characteristics and also phylogenetic similarity of 16S rRNA gene sequence. The optimal growth conditions for strain FBHYA2 were pH 6.0, 30 °C and 1.0% NaCl. Strain FBHYA2 can utilize naphthalene as the sole source of carbon and energy and was able to degrade naphthalene aerobically very fast, 48 h for 96% removal at 500 mg/L concentration. The physiological response of Achromobacter sp., FBHYA2 to several hydrophobic chemicals (aliphatic and aromatic hydrocarbons) was also investigated. No biosurfactant was detected during bacterial growth on any aliphatic/aromatic hydrocarbons. The results of hydrophobicity measurements showed no significant difference between naphthalene- and LB-grown cells. The capability of the strain FBHYA2 to degrade naphthalene completely and rapidly without the need to secrete biosurfactant may make it an ideal candidate to remediate polycyclic aromatic hydrocarbon (PAH)-contaminated sites.

Assessment and investigation on the fate of organochlorine pesticides in water and sediments of international Amir-kalaye wetland in north of Iran.

A total of 48 water samples and 24 sediment samples were collected at four sampling stations along the wetland during four seasons from 2009 to 2010 and analyzed by gas chromatograph-electron capture detector (GC-ECD). In water the total concentration of OCPs was 0.33, 0.01, 0.1 and 0.07 mg/L in summer, autumn, winter and spring, respectively. The most frequent OCP compounds detected were endrin and chlordane (0.08 and 0.07 mg/L), heaxachlorobenzene and chlordane (0.06, 0.02 mg/L), and chlordane (0.07 mg/L) in summer, winter and spring, respectively. The maximum concentration of ΣOCPs was found in samples collected from station 1 in summer (0.26 mg/L). In sediments the total concentrations of OCPs were 15.84 and 2.62 mg/g-dry weight (dw) in summer and winter, respectively. Chlordane was the most frequently found OCP compound, followed by lindane, 9.92 and 2.47 mg/g-dry weight (dw), respectively, in summer. While, lindane (2.52 mg/g-dw) and endosulfan I (0.1 mg/g-dw) were the highest OCP compounds detected in winter. The results obtained in this study show that there still exist a variety of organochlorine pesticide residues in the water and sediments from the Amir-kalaye wetland in Iran.