Inlet Benzene Concentration Research Articles

Use of NH4Cl for activation of carbon xerogel to prepare a novel efficacious adsorbent for benzene removal from contaminated air streams in a fixed-bed column

BackgroundAmmonium chloride as an explosive salt has proved to be a prominent activation agent for adsorbents and increase the specific surface area and volume of cavities. In this work, the ability of this substance was scrutinized for activation of carbon aerogel to prepare an efficient adsorbent for benzene removal from air streams.MethodsA carbon xerogel was fabricated from Novallac polymer and activated by ammonium chloride.The changes in structure and morphology were considered via Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), Barrett-Joyner-Halenda (BJH), and energy dispersive X-ray (EDX) analyses. Also, comprehensive studies were conducted to vouchsafe the properties of the new adsorbent for benzene removal, using a fixed-bed column mode.ResultsThe results showed both the successful synthesis and the suitability of the activation process. ACX possessed a higher specific surface area (1008 g/m3), compared to the parent carbon xerogel (CX; 543.7 g/m3) and organic xerogel (OX; 47 g/m3), as well as a higher adsorption capacity.ConclusionNH4CL is a very beneficial for modifying the structure and morphology of carbon aerogel, and the dynamic behavior of the column with respect inlet benzene concentration can be explained by Yan-Nelson model.

Preparation of Carbon-Alumina (C/Al2O3) aerogel nanocomposite for benzene adsorption from flow gas in fixed bed reactor

Benzene is one of the hazardous environmental pollutants which have harmful effects on human, animal and environmental health. the goal of this study was to synthesize a carbon/alumina aerogel with large surface area, which is easily recoverable and can be used as an adsorbent for benzene removal from the polluted air flow. The composite aerogel was dried at ambient temperature for 48 h and at 120 °C for 48 h in a sequential way. The characteristic properties of the composite aerogel were analyzed using Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), Barrett-Joyner-Halenda (BJH) method and energy-dispersive X-Ray (EDX) techniques. The findings of this study showed that, with increasing of the inlet flow rate from 0.2 l/min to 0.5 and 0.8 l/min, the breakthrough time decreased from 13 h to 7 and 3 h, respectively., Besides, the amount of adsorption capacity on aerogel nanocomposite decreased from 126.73 mg g−1 to 84.5 and 38 mgg−1 with increasing the inlet benzene concentration from 100 ppmv to 200 and 300 ppmv, respectively. In addition, the a carbon/alumina aerogel can be exploited for removing other pollutants from air and water.Recently, the adsorption process has attracted many research attentions for Benzene removal from different applications due to some inherent characteristics such as low-cost and high feasibility.•The results indicated that the synthesis of the composite aerogel have been successfully performed.•The composite aerogel was synthesized by combining Novollac with alumina, which had high surface area and suitable benzene adsorption ability.

Numerical Modeling on Benzene Dissolution into Groundwater and Transport of Dissolved Benzene in a Saturated Fracture-Matrix System

Dissolution from residual source zones of benzene poses serious threat to the groundwater quality. Proper understanding of fate and migration of dissolved benzene is a prerequisite for planning remediation strategies to reduce groundwater contamination. In the present study, an attempt has been made to numerically model the dissolution of benzene and to investigate the transport of aqueous phase benzene in a saturated fracture-matrix system under steady-state flow condition. In addition to dissolution mass transfer, advection, dispersion and matrix diffusion of aqueous benzene has been considered along the fracture. In the present numerical model, residual phase benzene is considered to be present along the entire length of the fracture and residual phase benzene is assumed to be immobile for the flow conditions considered in the analysis. Transport equations for fracture and rock-matrix are solved using implicit finite difference method. Transport equation for aqueous benzene within the fracture has been solved in a one-dimensional domain and transport equation for aqueous benzene within rock-matrix has been solved in a pseudo-two-dimensional domain. Sensitivity studies have been conducted to investigate the impact of variation of flow velocity, dispersivity, fracture aperture, inlet benzene concentration, rock-matrix diffusion coefficient, and half fracture spacing on transport of aqueous benzene concentration within the fracture. From the present study, it can be concluded that the addition of slow liquid benzene dissolution into aqueous phase influences the benzene breakthrough curves/profiles at different velocity, fracture aperture, initial benzene concentration, mass transfer rate, rock dispersivity and half fracture spacing.

Benzene Removal Using Non-thermal Plasma with CuO/AC Catalyst: Reaction Condition Optimization and Decomposition Mechanism

Non-thermal plasma (NTP) technology in synergy with adsorption catalysts was used to decompose volatile organic compounds. The obtained results indicated that the non-thermal plasma-assisted catalytic system (NTP-C) resulted in higher benzene removal capability and system energy efficiency. The CuO/AC (AC: active carbon) catalysts were prepared by incipient-wetness impregnation method, and effect of CuO loading on benzene destruction was tested. The effect of reaction conditions such as inlet benzene concentration, reaction space velocity, reaction humidity and energy density were also studied. Additionally, the reaction conditions were optimized by the multi-factor orthogonal experiment, and the highest benzene removal efficiency achieved 96.5 %. The influence degree of various factors for benzene elimination was: reaction space velocity ≫ CuO loading > energy density > inlet benzene concentration ≫ reaction humidity. Furthermore, the benzene decomposition mechanism was discussed by analyses of the reaction exhaust, the coke substance inside the reactor, and the surface property of the used catalyst. The oxidation byproducts primarily consisted of phenol and substitutions of phenol. We propose that the radical reactions play a significant role in benzene removal on the surface of catalysts.

Photodegradation of benzene by TiO 2 nanoparticles prepared by flame CVD process

Photodegradation of benzene at ppb levels by mixed-phase TiO 2 nanoparticles, synthesized by the oxidation of TiCl 4 in propane/air turbulent flame chemical vapor deposition (CVD) process, is investigated experimentally by using a tubular photoreactor with thin TiO 2 films coated on the reactor wall by sedimentation. Effects of inlet benzene concentration from 10 to 300 μg/m 3, rutile mass fraction from about 20 to 50% and photoluminescence (PL) intensity of TiO 2 nanoparticles on degradation degree are examined under the conditions of 70% relative humidity, 38 μg/cm 2 catalyst loading, 24 mW/cm 2 UV irradiation of 254 nm and 5.7 s residence time in the reactor. Based on experimental results, separation of photo-induced electron (e −) and hole (h +) pairs by rutile phase is discussed as photo-induced electron (e −) in anatase phase will migrate to rutile surface due to that the potential of conductive band of rutile is lower than that of anatase, leading to more holes ready on anatase surface for oxidation reactions.

A bioactive foamed emulsion reactor for the treatment of benzene-contaminated air stream

An adapted bioactive foamed emulsion bioreactor for the treatment of benzene vapor has been developed. In this reactor, bed clogging was resolved by bioactive foam as a substitute of packing bed for interfacial contact of liquid to gaseous phase. The pollutant solubility has been increased using biocompatible organic phase in liquid phase and this reactor can be applied for higher inlet benzene concentration. Experimental results showed a benzene elimination capacity (EC) of 220 g m(-3) h(-1) with removal efficiency (RE) of 85% for benzene inlet concentration of 1-1.2 g m(-3) at 15 s gas residence time in bioreactor. Assessment of benzene concentration in liquid phase showed that a significant amount of transferred benzene mass has been biodegraded. By optimizing the operational parameters of bioreactor, continuous operation of bioreactor with high EC and RE was demonstrated. With respect to the results, this reactor has the potential to be applied instead of biofilter and biotrickling filters.

Simulating a multiphase reactor with continuous phase transition

A novel multiphase fixed-bed reactor with continuous phase transition for benzene hydrogenation to cyclohexane has been presented by Cheng et al. (A.I.Ch.E. J. 47 (2001a) 1185; Chem. Eng. Sci. 56 (2001b) 6025; 57 (2002) 3407; A.I.Ch.E. J. 49 (2003) 225) which makes use of evaporation of volatile components to remove the reaction heat. This paper investigates issues related to the numerical simulation of the model for this novel fixed-bed reactor. The reactor is supposed to be divided into two parts subject to the phase transition point on the bed level, that is, the liquid-contacted zone at the lower part and the gas-contacted zone at the upper part. A steady-state mathematical model for the reactor is developed. All external mass and heat transfer resistances can be neglected in the case investigated, as well as temperature differences in the particles. The effects of feed inlet temperature, inlet benzene concentration, gas flow rate and liquid flow rate on the reactor performance are theoretically studied. Reliability of the model is verified by bench-scale experiments. The results show that dryout phenomena will occur in the reactor both on the bed-scale and on the pellet-scale under certain conditions.

Sugarcane bagasse as alternative packing material for biofiltration of benzene polluted gaseous streams: a preliminary study

Removal of benzene vapor from gaseous streams was studied in two identically sized lab-scale biofiltration columns: one filled with a mixture of raw sugarcane bagasse and glass beads, and the other one packed with a mixture of ground sugarcane bagasse and glass beads, in the same volume ratio, as filter materials. Separate series of continuous tests were performed, in parallel, under the same operating conditions (inlet benzene concentration of 10.0, 20.0 or 50.0 mg m −3 , and superficial gas velocity of 30.6, 61.2 or 122.4 m h −1 ) in order to evaluate and compare the influence of the packing material characteristics upon the biofilter effectiveness. The maximum elimination capacities obtained, at an inlet load of 6.12 g m −3 h −1 , were 3.50 and 3.80 g m −3 packing material h −1 with raw and ground sugarcane bagasse, respectively. This was a preliminary study and the results obtained suggest only a limited application with more work needed.

A trickling fibrous-bed bioreactor for biofiltration of benzene in air

A novel trickling fibrous-bed bioreactor was developed for biofiltration to remove pollutants present in contaminated air. Air containing benzene as the sole carbon source was effectively treated with a coculture of Pseudomonas putida and Pseudomonas fluorescens immobilized in the trickling biofilter, which was wetted with a liquid medium containing only inorganic mineral salts. When the inlet benzene concentration (C gi ) was 0.37 g/m 3 , the benzene removal efficiency in the biofilter was greater than 90% at an empty bed retention time (EBRT) of 8 min or a superficial air flow rate of 1.8 m 3 /m 2 .h. In general, the removal efficiency decreased but the elimination capacity of the biofilter increased with increasing the inlet benzene concentration and the air (feed) flow rate. It was also found that the removal efficiency decreased but the elimination capacity increased with an increase in the loading capacity, which is equal to the inlet concentration divided by EBRT. The maximum elimination capacity achieved in this study was ∼11.5 g/m 3 .h when the inlet benzene concentration was 1.7 g/m 3 and the superficial air flow rate was 3.62 m 3 /m 2 .h. A simple mathematical model based on the first-order reaction kinetics was developed to simulate the biofiltration performance. The apparent first order parameter K 1 in this model was found to be linearly related to the inlet benzene concentration (K 1 =4.64-1.38 C gi ). The model can be used to predict the benzene removal efficiency and elimination capacity of the biofilter for benzene loading capacity up to ∼30 g/m 3 .h. Using this model, the maximum elimination capacity for the biofilter was estimated to be 12.3 g/m 3 .h, and the critical loading capacity was found to be 14 g/m 3 .h. The biofilter had a fast response to process condition changes and was stable for long-term operation; no degeneration or clogging of the biofilter was encountered during the 3-month period studied. The biofilter also had a relatively low pressure drop of 750 Pa/m at a high superficial air flow rate of 7.21 m 3 /m 2 .h, indicating a good potential for further scale up for industrial applications.

A novel kinetic model discrimination method: eigenfunction distribution via forced concentration oscillation

Forced feed concentration oscillation, a special transient method, is developed for rival kinetic model discrimination. Time-dependent concentration samples are taken from four axial positions of an isothermal tubular reactor packed with catalyst pellets. Karhunen—Loeve expansion is used to find eigenfunctions of the reacting components for different kinetic models, on the basis of a biorthogonal function expansion of spatial concentration correlation. Oxidation of benzene to maleic anhydride over V 2O 5 is employed as a working system for which six possible mechanisms are postulated. The inlet benzene concentration is imparted a square-wave oscillation to study the response at various axial positions. Model discrimination has shown that two out of the six possible models merit further discrimination. Measured concentration snapshots of a time series are applied to determine the test eigenfunctions, which are then compared with those of the rival models. Agreement between calculated and experimentally determined eigenfunctions testifies to the validity of the present method of model discrimination.