Initial Toluene Concentration Research Articles

Application of ionic liquid-polymer gel membrane in toluene/n-heptane separation

The separation of aromatic and alkane is one of the most important and challenge chemical separation process. This study reports the high-efficiency separation of aromatics/alkanes in the pervaporation process based on a series of novel ionic liquid gel membranes. The ionic liquid gel membrane was characterized by FT-IR, SEM, AFM, TGA, and XRD techniques. The results revealed that the IL was maintained in the three-dimensional structure of polymer support and the membrane kept its stability when the temperature was over 300 °C. The relevant parameters i.e. polymer concentration, IL concentration, IL type, film-forming temperature, membrane thickness, feed concentration, operating temperature and feed flow rate on membrane process were investigated. The optimal membrane was prepared when the P(VDF-HFP) and [Amim][Tf2N] concentrations were 15 wt% and 45 wt%, the film-forming temperature was 15 °C and the membrane thickness was 120 μm. When the initial toluene concentration was 50 wt% and the flow rate was 200 mL/min, the best flux (120 g·m−2·h−1) and separation factor (11.3) were observed at 25 °C. Moreover, the separation factor was over 10 and the flux maintained at the same level after working continuously for 30 h, which indicates that the membrane has good stability.

Photocatalytic removal of toluene from gas stream using chitosan/AgI-ZnO Nanocomposite fixed on glass bed under UVA irradiation

In this study, AgI-ZnO/chitosan nanocomposite was synthesized and then was coated on 2×40×200 glass plates under UVA irradiation for the removal of toluene from air streams. The AgI-ZnO/chitosan Nanocomposite was characterized using XRD, SEM, FTIR and BET techniques. The analyses showed Zn and Ag were added to the composite structure with weight percentages of 32.02 and 7.31, respectively. The results confirmed that the AgI-ZnO/chitosan nanocomposite was successfully synthetized. According to the results, the photocatalytic process was able to remove 74.6% of toluene at an air flow rate of 1 L/min after 3.3 min. Also, by increasing the passing flow rate from 0.3 to 1.5 L/min through the photocatalytic reactor, the process efficiency for toluene removal increased. The toluene removal efficiency decreased with increasing relative humidity with respect to time. Moreover, increasing relative humidity decreased the photocatalyst capacity for the removal of the target pollutants. The results implied that the initial toluene concentration in the inlet stream played a key role on the photocatalysis of toluene and by further increase in the pollutant concentration higher than 20 ppm, its performance decreased dramatically. Therefore, the proposed process can be used and an effective technique for the removal of toluene from the polluted air stream under UV irradiation and increasing temperature up to 60 °C could increase its performance.

Study on catalytic removal of toluene by metal oxides derived from hydrotalcite

Hydrotalcite (HT) precursor was synthesized by coprecipitation method, and the surface of HT precursor was modified. The mixed metal oxide (MO) catalyst was prepared by calcination of HT precursor, which was used to remove toluene from VOCs assisted by NTP technology. The catalytic performance of MO catalyst was investigated. The results show that the MO catalyst with good structure can be obtained after calcination of HT precursor before and after modification. The results of catalytic performance test showed that the initial concentration of toluene was 700 ppm, the gas flow rate was 600 mL/min, and the reaction time was 30 min, SIE of NTP was above 3.0 kJ/L, the toluene conversion rate reached above 90%. MO assisted NTP had better catalytic performance with lower energy consumption. The toluene treatment capacity per unit energy consumption increased from 15.3% to 20.6%, which had an increase of 34.6%.

Synthesis of magnetic Fe3O4/AC nanoparticles and its application for the removal of gas-phase toluene by adsorption process

In this study, we present the first application of magnetic Fe3O4 functionalized with activated carbon (Fe3O4/AC) as nano-adsorbent for the removal of gas-phase toluene by adsorption process. Magnetic Fe3O4/AC was synthesized via co-precipitation method within the framework of nanotechnology principles. Then, the effects of process conditions such as contact time, initial toluene concentration, and temperature on the adsorption capacity of toluene by the magnetic Fe3O4/AC were investigated using the response surface methodology (RSM). The obtained magnetic Fe3O4/AC was characterized using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and thermogravimetric (TG) analysis. The maximum adsorption capacity of the magnetic Fe3O4/AC for the adsorption of the toluene was determined as 312.99 mg g-1 under optimal process conditions such as 59.48 min contact time, 17.21 mg l-1 initial toluene concentration, and 26.01°C temperature. The adsorption by the magnetic Fe3O4/AC indicated the best fit with the Langmuir isotherm model, and obeyed the pseudo-second-order (PSO) kinetic model. This study indicated that magnetic Fe3O4/AC could be applied as an adsorbent for the removal of gas-phase toluene.

Conjugated porous polymers for gaseous toluene adsorption in humid atmosphere

Two triphenylamine-based conjugated porous polymers, 1,3,5-triformylbenzene-4,4′4″-triaminotriphenylamine (TFB-TPA) and 2,4,6-triformylphloroglucinol-4,4′4″-triaminotriphenylamine (TFP-TPA) fabricated via Schiff-base reaction with π-conjugated skeletons and hierarchical pore structures were explored as adsorbents for the removal of gaseous toluene under humid environment. The effects of humidity, initial toluene concentration, adsorption temperature and surface functional groups on the adsorption capacity were investigated. The equilibrium isotherms, adsorption kinetics and structure-activity relationship were further analyzed. Experiment results suggest that the as-prepared TFB-TPA exhibits acceptable adsorption performance for gaseous toluene in humid atmosphere owing to the aromatic backbone and the hierarchically micro-meso-macroporous structure and the Freundlich equation agrees very well with the isothermal data, the pseudo-second-order kinetic model is more suitable to describe the adsorption kinetics. This study may not only show the application potential of triphenylamine-based conjugated porous polymers in toluene adsorption, but also provide a detailed understanding of the adsorption process of toluene for practical application.

Catalytic oxidation of toluene in air using manganese incorporated catalyst by non-thermal plasma system

Mn/MCM-41 and imp-Mn/MCM-41 catalysts were prepared in this study through metal heteroatom substitution and impregnation methods, respectively, and their catalytic oxidation performance of toluene under non-thermal plasma (NTP) in a dielectric barrier discharge reactor was studied. The stability of the catalyst and the parameters of catalytic oxidation conditions (initial concentration of toluene, O2 ratio, and relative humidity of carrier gas) were optimized. Characterization proved that the impregnation method resulted in the existence of manganese in the form of oxides (MnO2, Mn2O3) outside the pores of MCM-41. Meanwhile, the metal heteroatom substitution method implanted manganese into the mesoporous structure and replaced part of it with Si-O-Mn. NTP catalytic oxidation of toluene, ozone emission, and GC–MS by-product analysis confirmed that 60Mn/MCM-41 catalyst has high catalytic activity. Moreover, the catalyst affected the production of by-products. The stability test revealed that the 60Mn/MCM-41 catalyst still respectively reached 84.6% and 61% in the conversion of toluene and the selectivity of CO2 under the SED of 558 J/L after 40 h discharge reaction.

Fabrication and characterization of 3,4-diaminobenzophenone-functionalized magnetic nanoadsorbent with enhanced VOC adsorption and desorption capacity.

The present study, for the first time, utilized 3,4-diaminobenzophenone (DABP)-functionalized Fe3O4/AC@SiO2 (Fe3O4/AC@SiO2@DABP) magnetic nanoparticles (MNPs) synthesized as a nanoadsorbent for enhancing adsorption and desorption capacity of gaseous benzene and toluene as volatile organic compounds (VOCs). The Fe3O4/AC@SiO2@DABP MNPs used in adsorption and desorption of benzene and toluene were synthesized by the co-precipitation and sol-gel methods. The synthesized MNPs were characterized by SEM, FTIR, TGA/DTA, and BET surface area analysis. Moreover, the optimization of the process parameters, namely contact time, initial VOC concentration, and temperature, was performed by applying response surface methodology (RSM). Adsorption results demonstrated that the Fe3O4/AC@SiO2@DABP MNPs had excellent adsorption capacity. The maximum adsorption capacities for benzene and toluene were found as 530.99 and 666.00 mg/g, respectively, under optimum process parameters (contact time 55.47 min, initial benzene concentration 17.57 ppm, and temperature 29.09 °C; and contact time 57.54 min, initial toluene concentration 17.83 ppm, and temperature 27.93 °C for benzene and toluene, respectively). In addition to the distinctive adsorptive behavior, the Fe3O4/AC@SiO2@DABP MNPs exhibited a high reproducibility adsorption and desorption capacity. After the fifth adsorption and desorption cycles, the Fe3O4/AC@SiO2@DABP MNPs retained 94.4% and 95.4% of its initial adsorption capacity for benzene and toluene, respectively. Kinetic and isotherm findings suggested that the adsorption mechanisms of benzene and toluene on the Fe3O4/AC@SiO2@DABP MNPs were physical processes. The results indicated that the successfully synthesized Fe3O4/AC@SiO2@DABP MNPs can be applied as an attractive, highly effective, reusable, and cost-effective adsorbent for the adsorption of VOC pollutants.Graphical abstract.

Comparative study of degradation of toluene and methyl isobutyl ketone (MIBK) in aqueous solution by pulsed corona discharge plasma

Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds (VOCs), toluene and methyl isobutyl ketone (MIBK), in aqueous solution was evaluated. The plasma degradation of MIBK has been studied for the first time. The influence of initial concentration of target compound, solution pH and scavengers on percentage degradation was evaluated. 100% removal of 200 mg/L of toluene and MIBK was achieved both in liquid and gaseous phases after 12 and 16 min of plasma treatment, respectively. The first order rate constant of toluene and MIBK degradation (for 200 mg/L each) was 0.421 and 0.319 min−1 respectively when they were treated individually, and these values decreased slightly during degradation of their mixture. MIBK degradation was slower than toluene and it might be due to semi volatile and hydrophilic nature of MIBK. The effect of initial concentration of toluene and MIBK showed different degradation patterns. Highest degradation of both the compounds was obtained in neutral pH and in absence of scavengers. •OH radical was the major reactive species involved in their degradation. Their degradation in real environmental matrices showed that removal reduced significantly in secondary effluent due to scavenging of reactive species by various ions and organic matter. The total number of degradation intermediates identified in case of toluene and MIBK was 11 and 14 respectively and formate was the one recalcitrant byproduct generated. The degradation pathway of toluene and MIBK involving reactions of reactive oxygen and nitrogen species and reductive species is proposed.

Isotherm, kinetic, and thermodynamic studies for dynamic adsorption of toluene in gas phase onto porous Fe-MIL-101/OAC composite.

In the present paper, micro-mesoporous Fe-MIL-101/OAC composite using in situ incorporation of Fe-MIL-101 into oxidized activated carbon was synthesized and characterized by XRD, FT-IR, SEM, EDS, and BET techniques. The adsorption performances of toluene onto adsorbents in the gas phase were studied using a laboratory-scale dynamic adsorption system under moist ambience. The toluene adsorption capacity of Fe-MIL-101/OAC composite and Fe-MIL-101 were 127 and 97.6mgg-1, severally. Results revealed that the larger pores in micro-mesoporous Fe-MIL-101/OAC enhanced the molecular diffusion rate. The findings indicated that micro-mesoporous structures played key roles in the capture of toluene molecules. The initial toluene concentration positively affected on toluene adsorption capacity while temperature and humidity negatively affected on toluene adsorption capacity. The Langmuir model and the pseudo-second-order kinetics model described better adsorption process of Fe-MIL-101/OAC composite. Thermodynamic findings determined that toluene adsorption over Fe-MIL-101/OAC was spontaneous, exothermic physisorption. The regeneration of the composite was still up to 72.6% after six cycles. The micro-mesoporous Fe-MIL-101/OAC composite proposes a promising support for the high toluene removal for future. Graphical abstract.

Product analysis and mechanism of toluene degradation by low temperature plasma with single dielectric barrier discharge

A single dielectric barrier discharge (DBD) low-temperature plasma reactor was set up, and toluene was selected as the representative substance for volatile organic compounds (VOCs), to study the reaction products and degradation mechanism of VOCs degradation by low-temperature plasma. Different parameters effect on the concentration of O3 and NOx during the degradation of toluene were studied. The exhaust in the process of toluene degradation was continuously detected and analyzed, and the degradation mechanism of toluene was explored. The results showed that the concentration of O3 increased with the increase of the power density and discharge voltage of the plasma device. However, as the initial concentration of toluene increased, the concentration of O3 basically keep steady. The concentration of NOx in the by-products increased with the discharge voltage, power density, and initial concentration of toluene in the plasma device, and the concentration of NO2 was much higher than the concentration of NO. The degradation process of toluene was detected and analyzed. The results showed that the degradation mechanism of toluene by plasma includes high energy electron bombardment reaction, active radical reaction and ion molecule reaction. Among them, the effect of high-energy electrons on toluene degradation is the largest, followed by the effect of free radicals, in which oxygen radicals participated in the reaction mainly through the formation of C–O bond, CO bond, (CO)–O– bond and –OH radical, while nitrogen radicals participate in the reaction mainly through the formation of C–NH2, (CNH)- bond, CN bond and C–NO2 bond. The results can provide some data supports for the study of low-temperature plasma degradation of VOCs.

Insight into simultaneous catalytic oxidation of benzene and toluene in air over the nano-catalyst: Experimental and modeling via CFD-ANN hybrid method

This study reveals the simultaneous deep oxidation of benzene and toluene over the novel supported cobalt oxide catalyst derived from metal organic framework (MOF) over the almond shell based activated carbon. The performance of the fabricated catalyst was evaluated under the various operating conditions including oxidation temperature, initial concentration of benzene and toluene. The maximum conversion of benzene and toluene were also measured to be 89.74 % and 82.37 %, respectively. The sample morphology was studied by applying XRD, FESEM, BET and TGA analysis. The characterization tests indicated that the well dispersed spherical nano-supported catalyst was synthesized with size of less than 40 nm. To the best of our knowledge, the computational fluid dynamics (CFD) analysis incorporated with artificial neural network (ANN) was also studied for modeling the deep catalytic oxidation over the prepared sample. The modeling involved with the three dimensional analysis of polluted air flow through of a tubular micro-reactor axial inlet and outlet. The computational fluid dynamics was coded by adopting COMSOL Multiphysics to model the catalytic conversion of volatile organic compounds (VOCs) inside the porous media. The kinetic modeling was also conducted by using three-layer ANN to determine the reaction rates while the reaction temperature, initial concentration of benzene and toluene were considered as the input variables of network. The reaction rates were calculated by a non-linear feed-forward network with 5 neurons and log-sigmoid function in the hidden layer while the correlation coefficient was achieved to be 0.99. The validation of CFD model was accomplished which showed the appropriate matching between the experimental data and model achievements. Therefore, the developed intelligent hybrid model (CFD-ANN) in the offered investigation can be a useful tool for studying the fluid dynamics of VOCs oxidation over the nano-catalyst under the different operating conditions.

High-performance gas-phase adsorption of benzene and toluene on activated carbon: response surface optimization, reusability, equilibrium, kinetic, and competitive adsorption studies.

In recent years, volatile organic compounds (VOCs) have become a group of major pollutants that endanger human health and the ecological environment. The main purpose of this study was to investigate the gas-phase adsorption processes of benzene and toluene, which are important VOCs, on the activated carbon (AC) produced from Elaeagnus angustifolia seeds by physical activation method. In this context, the central composite design (CCD) approach-based response surface methodology (RSM) was applied to examine and optimize the effects of process parameters on the adsorption of benzene and toluene by AC adsorbent. The characterization of the produced AC was performed by the Brunauer-Emmett-Teller surface area, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The optimum process parameters were achieved (adsorption time of 74.98min, initial benzene concentration of 16.68ppm, and temperature of 26.97°C, and adsorption time of 73.26min, initial toluene concentration of 18.46ppm and temperature of 29.80°C) for benzene and toluene, respectively. The maximum adsorption capacities of benzene and toluene on AC were determined to be 437.36 and 512.03mg/g, respectively, under optimum parameters. The adsorption process kinetics and equilibrium isotherms were also evaluated. Besides, AC reusability studies were performed five times for the gas-phase adsorption and desorption of benzene and toluene. After five cycles, it was observed that the benzene and toluene adsorption capacity of the AC decreased slightly by 8.10% and 7.42%, respectively. The results revealed that the produced AC could be utilized successfully for the removal of benzene and toluene in the gas-phase adsorption systems because of its high surface area, high adsorption capacity, and high reusability performance. Furthermore, the adsorption processes of benzene and toluene were investigated, both sole components and in a binary mixture. It was concluded that the adsorption behaviors of benzene and toluene against AC were quite different when they were in the competition (in a binary mixture) and without competition (sole components). Graphical abstract.

Batch-scale remediation of toluene contaminated groundwater using PRB system with tyre crumb rubber and sand mixture

The objective of the study is to examine the potential of TCR (tyre crumb rubber) particles to remediate toluene contaminated aquifers by using them as the reactive constituent of permeable reactive barriers (PRB). The objective is achieved by performing laboratory experiments to identify toluene adsorption capacity and rate of toluene removal of the optimal TCR-sand mix. Adsorption isotherms and Kc-Co relations (Kc: distribution coefficient, Co: initial toluene concentration) identified the optimum mix (2.5 % TCR-97.5 % sand mix) for remediation of toluene contaminated water. Batch experiments showed that toluene adsorption by TCR particles is endothermic and is energetically favoured at higher temperature. Adsorption of the non-polar molecule by TCR particles obeyed bi-linear, pseudo first order kinetics. The carbon-black component of TCR particles adsorbed significant amount of toluene during the initial contact period (10−60 min). Scatchard analysis, Freundlich isotherm and DR (Dubinin-Radushkevich) equation indicated that toluene is adsorbed by van der Waals attraction at energetically heterogenous sites of TCR particles. The near irreversible toluene adsorption in the laboratory experiment is attributed to physical entrapment of the non-polar molecules in the medium and fine pores of TCR particles. Batch experiment results predict that unit PRB column constructed with 2.5 % TCR-97.5 % sand mix can remediate 11,013 K L of toluene contaminated (0.15 mg/L) groundwater near instantaneously.

Degradation of toluene by pulse-modulated multistage DBD plasma: Key parameters optimization through response surface methodology (RSM) and degradation pathway analysis

In the present work, a pulse-modulated high-frequency (HF) dielectric barrier discharge (DBD) plasma has been employed and utilized to evaluate the feasibility of toluene degradation in a multistage rod-type reactor at room temperature. Experimental result indicates that the energy consumption is significantly reduced and heating effect can be effectively suppressed when the DBD plasma is ignited in pulse-modulated mode instead of continuous mode.The response surface methodology (RSM) based on central composite design (CCD) model has been proposed to evaluate the contribution of key operating parameters including duty cycle and modulation frequency. The proposed model offers a good fit for actal data. The contribution of the modulation frequency is observed to be more dominant compared to the duty cycle for both the degradation efficiency and the energy yield. According to the results provided by the proposed model, the toluene degradation efficiency of 62.9 % and the energy yield of 0.90 g/kWh are obtained under the optimal conditions of 400 Hz modulation frequency and 56 % duty cycle. The effect of initial toluene concentration and gas flow rate have also been investigated. Increasing toluene initial concentration and gas flow rate are found to be unfavorable for the degradation of toluene, however, which are of benefit to the energy yield. A long-time experiment to assess the stability of pulse-modulated DBD has been successful performed. The possible pathways in plasma degradation of toluene is proposed based on the intermediates identification using GC–MS and FTIR.

Introduction of amino and rGO into PP nonwoven surface for removal of gaseous aromatic pollutants and particulate matter from air

Gaseous aromatic pollutants such as benzene, toluene or xylene and particulate matter (PM) from an individual’s living environment potentially cause serious and life-threatening health problems. A new bifunctional individual protection material was prepared by grafting polymerization and electrostatic self-assembly method. The individual protection material has a dual function layer consisting of an amino-functionalized nonwoven grafted with dimethylaminoethyl methacrylate (DMAEMA) and a gaseous aromatic pollutant adsorption layer made up of reduced graphene oxide (rGO). The surface composition and structure of materials were obtained by a series of characterization methods. Adsorption and filtration performance for each function layer and double function layer Polypropylene (PP) nonwoven were intensively studied. As indicated by the experiments, the adsorption efficiency of PP-g-DMAEMA/rGO increased with the decreasing oxygen content of GO and increasing the initial concentration of toluene, filter performance and aperture parameters data showed that the surface Zeta potential and pore size had great influence on filtration efficiency of the filter material, the resulting PP nonwoven exhibited prominent multifunctional performance, including a higher adsorption amount (39.1 mg/g) and filter efficiency (72.2%). Consequently, it is expected that the bifunctional PP nonwoven will have potential applications in air purification for the removal of gaseous aromatic pollutants and PM.

Decomposition of Toluene in Coupled Plasma-Catalytic System

The study of toluene conversion, in a gas such as the one obtained during the pyrolysis of biomass, was conducted at atmospheric pressure in homogeneous and in coupled plasma-catalytic systems. The effects of discharge power, initial concentration of toluene, and the presence of the bed of NiO/Al2O3 - G-0117 (industrial catalyst for methane water shift) on the conversion of C7H8, the composition of the outlet gas, and its calorific value have been investigated. The gas flow rate was 1000 Nl/h and the initial gas composition was CO (0.13), CO2 (0.12), H2 (0.25), and N2 (0.5). The initial toluene concentration was in the range of 2000–4000 ppm. The obtained results show that the conversion of toluene increases with discharge power and the highest one was obtained in the coupled plasma-catalytic system. It was higher than that in the homogeneous system of gliding discharge plasma. The composition of gas changed within the range of a few percent. In the outlet gas acetylene, ethylene and ethane were observed. Trace amounts of toluene were reduced to benzene and formed C3 and C4 hydrocarbons. In an extended process, the reduction of NiO to metallic nickel, methanation reaction of carbon oxides, and an increase of the conversion of toluene were observed. The conversion of toluene in the extended process was 92%. The catalytic activity of G-0117 in a coupled system increased during the study conducted for about 40 min. The use of G-0117 catalyst led to an increase in the calorific value of the outlet gas. In every examined system, it was above the minimal level demanded by engines and turbines. After the process, carbon deposits were present.

Low temperature catalytic ozonation of toluene in flue gas over Mn-based catalysts: Effect of support property and SO2/water vapor addition

In this paper, three kinds of Mn-based catalysts over γ-Al2O3, SiO2 and TiO2 were synthesized to evaluate the toluene catalytic degradation by ozone under the related industrial conditions (i.e., temperature, SO2 and water vapor addition). Results show that the total acid and Mn3+ content on catalyst surface have a positive correlation with catalytic activity, thereby MnOx supported on γ-Al2O3 achieving the highest toluene conversion and ozone decomposition efficiency. Key operating parameters of reaction temperature, initial toluene concentration and O3/C7H8 ratio were investigated over MnOx/γ-Al2O3 to get the optimal daily operation condition. The suitable temperature range was 100∼120 °C, whereas too high or too low temperature both inhibited catalytic activity. Catalyst poisoning occurred as SO2 or water vapor was added, but fortunately, the toluene conversion efficiency could recover once SO2 or water vapor was stopped. Finally, in-situ DRIFTS measurement was carried out to reveal the reaction process and SO2 effect.

Comparison of single and double dielectric barrier discharge non-thermal plasma for toluene removal

In order to investigate the effect of dielectric barrier discharge (DBD) reactor structure on toluene degradation in non-thermal plasma, reactors with single and double barrier were designed. The discharge characteristics, toluene removal efficiency, mineralization rate, CO2 selectivity and energy efficiency of the two rectors were compared, and the effects of voltage and initial concentration on toluene degradation were analyzed. The results indicated that DDBD reactor had higher electric field strength and SDBD reactor had higher power under the same applied voltage. The removal efficiency of toluene in the DDBD reactor ranged from 9.4%~100%, 7.4%~99%, 5.1%~64% and that in the SDBD reactor ranged from 67%~98%, 46%~90%, 26%~59%, when the initial toluene concentration and the applied voltage were 616, 1 027, 1 848 mg·m−3 and were 14~24 kV, respectively. It showed that SDBD has a higher toluene removal efficiency at low applied voltage, while the removal efficiency is higher in DDBD at a higher applied voltage. Moreover, the decrease of toluene concentration and the increase of applied voltage were favorable for toluene degradation. In SDBD, the energy efficiency decreased with the increase of applied voltage, while that of the DDBD reactor first increased and then decreased. The energy efficiency of the DDBD reactor was higher than that of the SDBD reactor at 16~24 kV. The present study could provide reference for the application of DBD in VOCs abatement.

Preparation and Application of CO2-Triggered Switchable Solvents in Separation of Toluene/n-Heptane.

Extraction is a common approach to separating aromatics and alkanes, but solvent recovery remains an issue. The polarity, hydrophobic/hydrophilic balance, and other properties of switchable solvents can be reversibly changed in the presence of various triggers, and taking advantage of this property can greatly simplify the process of solvent recovery. In this work, quaternation and anion exchange were used to prepare several switchable solvents by introducing OH- ions to derivatives of the amidine compound 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The resulting compounds exhibited reversible switching in response to exposure to CO2. Using toluene/n-heptane as a model hydrocarbon mixture, a reversible phase change extraction process was established. Among the four switchable solvents prepared, [C2DBU]OH showed the highest selectivity value and so was used to investigate the effect of various parameters on hydrocarbon separation. The extraction process was found to rapidly reach equilibrium when a two-phase system was generated by bubbling CO2 through the extraction mixture. Increasing the proportion of the solvent increased the selectivity for toluene, while a 1:1 ratio between the solvent and the toluene/n-heptane mixture enhanced the extraction. Increasing the initial toluene concentration reduced the selectivity for toluene, with a value of 5.97 at a toluene concentration of 20%. The switchable solvent recovered its initial state when heated at 60 °C for 1 h. Upon being reused after removal of CO2, the solvent exhibited poor separation characteristics, although the selectivity coefficient remained constant at approximately 3.1 during 10 regenerations. Finally, the mechanism of the switchable solvent effect and modeling of experimental data were investigated.

Toluene–degrading activity of local bacteria isolated from contaminated sea of North Sumatera

Hydrocarbon contamination in soil and water is still a major concern and considered as a serious environmental issue to various natural habitats. Microbial degradation of hydrocarbon compounds is considered as one of eco-friendly method to overcome this issue of contamination. Toulene-degrading bacteria were successfully recovered from contaminated marine seawater of Belawan and Tanjung Balai, North Sumatera. Three bacterial isolates identified as Pseudomonas aeruginosa TJB01, Pseudomonas sp. TJB05, and Acinetobacter sp. SBG05 were subjected to degradation test by evaluating their hydrocarbon-degrading activities towards Toluene as one of selected hydrocarbon compounds of BTEX. Parameters observed in this study were bacterial cell density (Colony-forming unit/mL) by using Total Plate Count method and hydrocarbon residues (ppm) quantified by using Gas Chromatography. Initial concentration of Toluene was detected 173.10 ppm. Isolate P. aeruginosa TJB01 produced the highest cell density (log 7.94 CFU.mL−1) and produced the highest toluence degradation (%) at 59.46% than other isolates and bacterial consortium during 12 days of incubation period. Further investigations are needed to optimize consortium potential in exhibiting better degradation activities.