N-hexane Concentration Research Articles

Prediction of the Phytochemical Properties of Luffa Cylindrica Seed Oil Using Artificial Neural Network

The research used an artificial neural network (ANN) to examine optimum extraction conditions and phytochemical contents of Luffa cylindrica seed oil. The oil yield was predicted using an artificial neural network. The performance of the ANN and response surface methodology models was compared. The optimum extraction yielded 7.567% oil yield, 185.676 mg/l phenol, and 45.087 mg/l terpineol at 75.57 °C extraction temperature, 5.77 h extraction time, and 10.68 g/mol n-hexane concentration, respectively. These data show that the oil output is poor but has a significant phenol and terpenoid content that may be employed in pharmaceutical sectors. The FT-IR analysis of Luffa cylindrica seed oil revealed a high level of unsaturated hydrocarbons and esters, making the oil appropriate for using in the paint industry and creating cosmetics.

Performance of a single-stage recuperative high-temperature air source heat pump

• A single-stage recuperative high-temperature air source heat pump is developed. • Exergy efficiency of 27.97% is higher than the existed heat pumps. • Discharge pressure is less than 2 MPa at the hot water temperature 91.68 °C. • n-hexane concentration is 52.36% shifted at optimal condition. Heat energy of 75–100 °C is increasingly used in residential and industrial fields. However, conventional single-stage air source heat pumps suffer low efficiency and poor operating conditions when supplying such high-temperature heat energy. To address the challenging problems, a novel single-stage recuperative high-temperature air source heat pump prototype for tap water direct heating was developed and investigated experimentally. The intrinsic characteristic of the recuperative heat pump makes the prototype simple and components easy to gain. The key impacts of the throttle valve opening, refrigerant concentration, and water flow rate on the system performance were revealed and analyzed with the refrigerant mixture of n-hexane and propylene. Results show the excellent thermodynamic efficiency and working condition of the developed heat pump. When heating water from 23.70 °C to 91.68 °C, the system shows its optimal performance with the coefficient of performance, exergy efficiency, and compression ratio 2.83, 27.97%, and 2.86, respectively. Furthermore, based on the experiment data, systematic thermodynamic analysis on optimal condition indicated that the mass fraction of n-hexane in the cycle is about 52.36% shifted against the initial charging proportion of 36%. Finally, after system performance comparison against the CO 2 transcritical heat pump and auto-cascade heat pump, the recuperative high-temperature heat pump shows excellent efficiency and nice operating condition, which proves the developed heat pump a successful and promising application prospect.

Cobalt doped nitrogenous porous carbon derived from covalent organic framework as cataluminescence catalyst for rapid determination of n-hexane in edible oil

In this work, a catalytic material of cobalt doped nitrogenous porous carbon (Co/NPC) was fabricated from covalent organic frameworks (COFs) and cobalt ion via directly carbonization. Attribute to the excellent selective catalytic performance towards n-hexane, Co/NPC was employed in cataluminescence (CTL) for rapid and sensitive determination of n-hexane. Moreover, the detection conditions of CTL were evaluated, including temperature, flow rate and detecting wavelength. Under optimized conditions, a good linear relation between signal intensity of CTL and n-hexane concentration was obtained in the linear range of 0.4–250.0 mg/L and the limit of detection (LOD, S/N = 3) was 0.13 mg/L. Furthermore, the Co/NPC based CTL sensor was successfully applied to the determination of n-hexane in edible oil samples with the recoveries in the range of 92.0%–104.0%. The method comparison results of GC/MS and CTL on real sample analysis further proved the accuracy of the developed Co/NPC based CTL method. Additionally, the possible catalytic mechanism of n-hexane on the surface of Co/NPC was investigated, assisting by GC/MS on intermediation products identification. Overall, the Co/NPC based CTL sensor has been confirmed excellent performance in the n-hexane determination, which revealing extensive application in rapid residual n-hexane analysis in edible oil.

Pd/HZSM-5 catalyst for n-hexane isomerization: Properties, activities, and deactivation

The activity of n-hexane isomerization with 0,8 %kl Pd/HZSM-5 was studied in a micro reactor in the temperature range of 225-325 oC at 0,1 Mpa with the molar ratio H2/ hydrocarbon of 5.92, n-hexane concentration of 9.2 %mol, GHSV 2698 h-1 at atmospheric pressure. The catalyst owned suitable acidity, reasonable reductivity, good metal dispersion, and appropiate balance between metallic and acidic functions. The catalyst had high activity but low stability. The cause of deactivation was examined via a comparison of physico-chemical properties between a fresh catalyst and a used one. There was no metal sintering. The mono-metallic catalyst performed high activity for n-hexane hydro-isomerization but less stable. Deactivation is mainly attributed to coke formation. Catalyst activity and stability were significantly improved with activity of 0,7 MPa compared to that of 0,1 MPa at elevated pressure. The catalyst Pd-Co/HZSM-5 is capable of resisting against coke, thereby exhibiting high stability at 0,1 MPa. The highly stable and active catalyst helped to form high quality products to result in environment-friendly gasoline.

Experimental and simulation analysis of hexane leak in pump room

The technology of monitoring and tracing the unorganized emissions of VOCs in petrochemical parks is a research hotspot. For the VOCs leakage in the pump room of the aromatics extraction equipment, 6 distributed monitoring points are implemented to monitor the VOCs concentration. A 2-hour leak test is performed using n-hexane standard gas, and the process is simulated using computational fluid dynamics. The results show that there is a background value of n-hexane concentration in the pump room, which means that potential leakage occur. P36, P19, P18, and P15 were able to respond to the n-hexane leak, but the concentrations of P14 and P17 y did not increase. The leakage sequence of simulation is the same as that obtained in the experiment. The concentration distribution is affected by the wall barrier and distance, and n-hexane will preferentially diffuse along the wall.

Improved degradation of n-hexane vapours using a hybrid system, a photoreactor packed with TiO2 coated-scoria granules and a multilayer biofilter.

Biofiltration of hydrophobic and/or recalcitrant volatile organic compounds such as n-hexane is imperfect. In the present study, we applied a hybrid system consisting of a photoreactor packed with scoria granules coated with TiO2 and a biofilter to improve the removal efficiency of n-hexane from the air stream. The experimental results showed that the hybrid system provided higher removal efficiencies than the single biofilter process with an inlet n-hexane concentration range of 0.11-1g-3 for empty bed residence times (EBRTs) of 30-120s in the hybrid system. The removal efficiency of the single biofilter in EBRTs of 30, 60 and 120s was 10.06%, 21.45%, and 45.98%, respectively. When the photoreactor was included as a pretreatment system (with residence time of 7-27s) and the overall EBRTs of the system was adjusted to 30, 60 and 120s, the removal efficiency of the hybrid system was increased to 39.79%, 63.08%, and 92.6%, respectively. The mass ratio of carbon dioxide produced as an indicator for n-hexane degradation in the hybrid system and the biofilter alone was 1.9 and 1.28, respectively. Bacterial community analysis with sequence analysis of 16S rDNA in the biofilter biomass revealed that Pseudomonas and Bacillus as predominant bacterial species were responsible for n-hexane biodegradation. Therefore, the application of the hybrid system is advantageous in enhanced n-hexane removal from the air stream.

Decomposition of n-hexane using a dielectric barrier discharge plasma

ABSTRACT In this study, we investigated the decomposition characteristics of n-hexane by a dielectric barrier discharge (DBD) plasma. In order to accomplish this, the factors influencing these decomposition characteristics such as background gases (air, N2, and He), residence time (1–10 s), initial n-hexane concentration (10–50 ppm), relative humidity (2.5%, 40%, and 70%), and power (50–80 W) were evaluated. As a result, the decomposition efficiency of n-hexane at N2 atmosphere was found to be lower than those at air and He atmosphere. The removal efficiency of n-hexane was increased when the residence time, relative humidity, and power increased, and when the initial concentration decreased. The concentrations of CO, CO2, and aerosol increased as the specific energy density increased. However, the O3 level increased up to a certain point, then decreased. Various hydrocarbons such as acetone, pentanal, nonanal, etc. were also detected as by-products and their decomposition and recombination pathways were suggested.

Simultaneous degradation of n-hexane and production of biosurfactants by Pseudomonas sp. strain NEE2 isolated from oil-contaminated soils.

The presence of surfactants in biofilters could enhance hydrophobic VOC removal. In this study, blood agar plate, methylene blue agar plate and a culture with n-hexane as the only carbon source were used to screen strains that could biodegrade n-hexane and produce biosurfactants simultaneously. The effects of n-hexane concentration on n-hexane removal and biosurfactant production were also investigated. Results showed that such a strain identified to be Pseudomonas sp. Strain NEE2 was successfully isolated from oil-polluted soils. The biosurfactants production by this strain were dependent on the initial concentration of n-hexane (132-2640 mg/L). At the concentration of 2640 mg/L of n-hexane, the biosurfactants promoted n-hexane removal. At 132 mg/L of n-hexane, n-hexane removal efficiency on day 2 exceeded 60%. The synergistic mechanisms of n-hexane removal and biosurfactant production by Pseudomonas sp. Strain NEE2 were discussed including the enhanced mass transfer from gas to liquid phase, within the biofilm phase and biodegradation at the presence of biosurfactants as well as the consequently enhanced production of the biosurfactants. These results in this study proved that it is possible for microorganisms utilizing the synergistic effect of hydrophobic VOC degradation and biosurfactant production for cost-effective hydrophobic VOC removal in biofilters.

Enhancement of pyocyanin production by Pseudomonas aeruginosa via the addition of n-hexane as an oxygen vector

Abstract Pseudomonas aeruginosa is capable of producing a wide range of industrially important biotechnological products like pigment, biosurfactants, enzymes, etc. Pyocyanin is a pigment produced by P. aeruginosa and widely used in many industries such as food, agriculture, pharmaceuticals and cosmetics. In order to increase the production of pyocyanin, in this study, the effects of previously untested oxygen vectors on P. aeruginosa OG1 pyocyanin production were studied. The oxygen vectors (n-hexadecane, n-dodecane and n-hexane) were compared in terms of pyocyanin production. All of the oxygen vectors were found to exhibit a stimulatory effect on pyocyanin production and the best result (11.96 mg/L) was obtained with n-hexane. In the next step, pyocyanin production in the presence of n-hexane, was optimized by response surface methodology. In addition to the n-hexane concentration, the optimum size of inoculum and the time of n-hexane addition to the fermentation liquid were investigated. Experimental design and the results were analysed by using Box-Behnken design of Response Surface Methodology (RSM). Accordingly, the optimum size of inoculum was found to be 2.07%, n-hexane concentration was 3.48% and the addition time was 33.93 h and at these optimum values, the amount of pyocyanin increased 2-fold (21.2 mg/L). According to these results, n-hexane addition as an oxygen carrier could be a useful technique in industrial production of pyocyanin.

Ignition characteristics of dual-fuel methane-n-hexane-oxygen-diluent mixtures in a rapid compression machine and a shock tube

Ignition delay times of methane-n-hexane-oxygen-dulent mixtures were studied experimentally and numerically in a wide temperature range (640–2335 K) using both a rapid compression machine (RCM) and a shock tube (ST). The RCM results demonstrated a two-stage ignition and negative temperature coefficient (NTC) behavior. Increasing n-hexane concentration, pressure and equivalence ratio shortened the ignition delay time. For the ST experiments, the addition of 10% n-hexane (relative to methane) can reduce the ignition delay time dramatically. However, no further reduction effect can be achieved with increasing addition of n-hexane from 10% to 20%. In addition, increasing equivalence ratio reduces the effect of n-hexane addition on ignition delay time. Three detailed chemical mechanisms, CaltechMech, GalwayMech and LLNLMech, were evaluated based on a quantitative error analysis. LLNLMech and CaltechMech demonstrated the best performance in the RCM and ST temperature ranges, respectively. Chemical kinetic analyses showed that the addition of n-hexane to methane provides some chemical pathways not available for methane oxidation which result in the production of active radicals and eventually accelerate the ignition of the methane-oxygen mixtures. The crucial intermediate species for the ignition process are H2O2 and H under RCM and ST conditions, respectively.

Total Plate Count Analysis Of Tuna Fish Adulterated With Lard In Order To Improve Halal Products

Indonesia is the country with the largest level of Muslim population in the world. Guarantees for the safety and protection of consumers in the food sector must be considered. One of the parameters used in product halal is total microbial analysis. The sample used was processed tuna which is adulterated with lard (1: 1). The research method uses Factorial Completely Randomized Design method which consists of two factors, Factor I: Solvent Concentration (K) consists of 4 levels, namely: K1 = 20%, K2 = 30%, K3 = 40%, K4 = 50%, Factors II: Maseration Time (W) consists of 4 levels : W1 = 06 Hours, W2 = 12 Hours, W3 = 18 Hours, and W4 = 24 Hours. The results showed that the n-hexane concentration had a very significant effect (p <0.01) on the total microbial parameters. The highest total microbes were in the 50% (K4) concentration of 4,337 log CFU / ml (2.2x104 CFU / ml) and the lowest value was in the treatment concentration of 20% (K1) which was 4,216 log CFU / ml (1.7x104 CFU / ml). The average microbial total value in the treatment of solvent concentration (K) obtained was 2.0x104 CFU / ml. The treatment of maceration time also gave a very significant effect (p <0.01) on the total microbial parameters. The highest total microbial was 24 hours treatment = 4,410 log CFU / ml (2,6x104 CFU / ml) and the lowest value was at 6 hours treatment which was 4,173 log CFU / ml (1.5x104 CFU / ml). Total microbial analysis provides information on adulteration of lard in processed food products in support of halal certification

Analisis Mikrobiologi Forensik Total Mikroba Sosis Sapi yang Bercampur Lemak Babi dalam Rangka Kehalalan Produk

Halalness of a food product is an important factor as a consideration in consuming it. Raw materials and additives used will affect the halality of the product. The food that we called to be halal if it does not contain pork including lard. This study was applied of the forensic microbiological analysis in assessing the total microbes contained in sausages containing lard. The aim of the study was to analyze the total microbes in beef sausages mixed with lard. In this total microbial analysis, a factorial Completely Randomized Design (RAL) method was used. Factor I is Solvent Concentration (K) which consists of four levels (K 1 = 20%, K 2 = 30%, K 3 = 40%, K 4 = 50%) and Factor II is Maseration Time (W) which consists of four levels (W 1 = 6 Hours, W 2 = 12 Hours, W 3 = 18 Hours, W 4 = 24 Hours). The results showed that the n-hexane concentration in beef sausage samples : lard (1: 1) gave a very significant effect (P> 0.01). The highest number of microbes was found in K 1 (9487,500) and the lowest was in K 4 (3887,500). The maceration time had a different effect that was not significant (P <0.05). The highest number of microbes is found at W 4 (8475,000) and the lowest at W 1 (5387,500). Treatment interactions had no significant effect (P <0.05).

Enhanced biodegradation of n-hexane from the air stream using rhamnolipid in a biofilter packed with a mixture of compost, scoria, sugar beet pulp and poplar tree skin

Biofiltration of n-hexane vapors with and without using rhamnolipid biosurfactant was investigated on a laboratory scale biofilter packed with compost, scoria, sugar beet pulp, and poplar tree skin at empty bed residence times (EBRT) of 30, 60 and 120s for a period of 131 days. Acclimation of microorganism in the biofilter was achieved in 31 days with an average n-hexane concentration of 0.269 gm −3 and EBRTs of 120s. The results demonstrated that average removal efficiencies (RE) for the corresponding EBRT with n-hexane loading rates (IL) of 6.7–137 gm −3 h −1 were 18.7 ± 1.67%, 28.9 ± 4.06% and 46.8 ± 8.2% without biosurfactant. While, the average REs in presence of the biosurfactant were 23.98 ± 4.08%, 42.4 ± 9.7% and 85.13 ± 10.44% at EBRTs of 30, 60 and 120s, respectively. About 53% of n-hexane removal was related to the segment 1 of the biofilter, where the bacterial and fungi population of its biofilm was 2 × 10 15 and 1.3 × 10 9 CFU g −1 (dry weight), respectively, which was significantly more than the other segments. For all the tested inlet concentrations, the RE was significantly increased by increasing EBRT and decreasing IL of n-hexane. The results of this study confirm the efficiency enhancement of rhamnolipid in biofiltration of hydrophobic compounds such as n-hexane from air streams. • Biofiltration of n-hexane vapors was investigated in the presence and absence of rhamnolipid biosurfactant. • Removal efficiency of n-hexane increased from 46 to 86% in the presence of rhamnolipid. • About 53% of n-hexane removal was related to the segment 1 of the biofilter. • Increasing the biofiltration of hydrophilic compounds by rhamnolipid.

Captures of oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae), in traps baited with host-plant volatiles in Chile

Studies in Australia and China identified host-plant volatile blends from peach and pear that captured relatively high numbers of Grapholita molesta (Busck). To determine if these blends are attractants in other countries and relative to each other, the two host-plant blends, a laboratory blend identified in Switzerland, and a new “total blend” made by mixing components of all three blends, were field-tested in Chile for the first time. The same solvent type, concentrations, and dispensers as in the original studies, plus an additional concentration and solvent, were used. Only the Swiss blend at the low n-hexane concentration captured significantly more males than the solvent traps, albeit in very low numbers (1.46 ± 1.46, mean ± SEM males/trap/week). Furthermore, host-plant blends decreased male captures in sex pheromone traps, and the effect was dose-dependent for the Chinese and total blends. A laboratory flight tunnel test confirmed the lack of G. molesta male response to the Australian, Chinese, and Swiss plant blends. In the flight tunnel, however, the males responded sooner and in higher numbers to mixtures of sex pheromone with host-plant blends than they did to the sex pheromone alone.

The diminishment of specific heat and surface tension of coolant droplet in a dropwise evaporation process: A novel methodology to enhance the heat transfer rate

ABSTRACTThe rate of dropwise evaporation is significantly altered by additives, such as benzene, n-hexane and acetone in water. These additives change some of the thermal and physical properties of the coolants, which have significant impact on various parameters that controls the droplet evaporative cooling, such as sensible, heat extraction period, droplet momentum and contact area. The open literature does not reveal the effects of the aforesaid additives on the dropwise evaporation. Therefore, in the current work, an attempt has been made to investigate the effects of above-mentioned additives on dropwise evaporation rate and reveal the mechanism involved. The droplet evaporative cooling experiments are conducted on a 2 mm thick AISI 304 steel plate (10 × 10 mm). The result shows that with increment in benzene and n-hexane concentration in water, the evaporation time significantly reduces. This is attributed to the decreasing surface tension, specific heat and contact angle. However, in case of acetone, the reduction in evaporation time is achieved only up to a concentration of 300 ppm, beyond which the evaporation time increases. This is because of the significant consumption of time in recoiling of the droplet. In addition to the above, the mechanism for the aforesaid enhancement process is tried to reveal by developing the models. For the validation of the developed equations, experimental results are compared with the numerically computed data. The comparison discloses that the developed model is quite accurate and shows insignificant variation from the experimental results. R2 and RMSE are also calculated for both the developed models and based on minimum recommended RMSE; the best model is also suggested.

N-Hexane intoxication in a Chinese medicine pharmaceutical plant: a case report

Backgroundn-Hexane is a well-known neurotoxicant. Polyneuropathy due to occupational n-hexane exposure has been reported worldwide, however, our case is the first report in the Chinese herb industry.Case presentationA 25-year-old Asian man experienced progressive weakness and numbness in his hands and feet after working as an operator in a Chinese medicine pharmaceutical plant for the manufacture of Chinese herbal pain relief patches for 10 months. Electrophysiological studies indicated a reduction in nerve conduction velocity, prolongation of distal latencies, mildly positive sharp waves, and reduced recruitment with polyphasic potentials, particularly at distal sites. Demyelination with axonal degeneration caused by occupational n-hexane exposure was strongly suspected. Through investigation of our patient’s workplace, the ambient n-hexane concentration in air was found to considerably exceed the permissible exposure limit/time-weighted average for n-hexane in Taiwan. His symptoms were gradually relieved after 4 months of cessation of exposure to n-hexane. He was then confirmed as a case of occupational n-hexane intoxication. Further effective control measures should be implemented as soon as possible to prevent exposure of workers to n-hexane.ConclusionsDespite a typical clinical presentation, his exposure at workplace was appropriately investigated. Chemical exposure in Chinese medicine pharmaceutical plants could be an emerging issue that may affect workers’ health. The lack of knowledge and management of solvents could endanger the health of workers. This case has profound educational implications for occupational health and is worthy of further follow-up for improving hazards control.

Three-liquid-phase salting-out extraction of effective components from waste liquor of processing sea cucumber

A three-liquid-phase (TLP) salting-out extraction system composed of n-hexane/ethanol/sodium carbonate/water was investigated to extract oils, saponins, proteins and polysaccharides simultaneously from waste liquor of processing sea cucumber. The effects of the ratio of ethanol to sodium carbonate, n-hexane concentration and extraction time were investigated. The results showed that 86.7% of oils were distributed in the top n-hexane phase, 82.9% of saponins in the middle ethanol phase, 93.2% of proteins and 92.9% of polysaccharides in the interface between the middle and the bottom salt phase when the system composed of 28% (w/w) n-hexane/11.52% (w/w) ethanol/8.64% (w/w) sodium carbonate was used at 37°C for 0.5h. When the system was progressively enlarged from 30g to 25kg, the yield of polysaccharides, proteins, oils and saponins was decreased only by 1.0%, 2.8%, 1.0% and 2.6%, respectively. The recycle of salt and solvents in three-liquid-phase system was also studied, and the results showed that the recovery of n-hexane, ethanol and salt were 81.4%, 80.8% and 72.0%, respectively. Recycling materials for the extraction, the yield for proteins and oils decreased by 2.0% and 5.4%, respectively, comparing with the pure system.

Inhibition of residual n-hexane in anaerobic digestion of lipid-extracted microalgal wastes and microbial community shift.

Converting lipid-extracted microalgal wastes to methane (CH4) via anaerobic digestion (AD) has the potential to make microalgae-based biodiesel platform more sustainable. However, it is apparent that remaining n-hexane (C6H14) from lipid extraction could inhibit metabolic pathway of methanogens. To test an inhibitory influence of residual n-hexane, this study conducted a series of batch AD by mixing lipid-extracted Chlorella vulgaris with a wide range of n-hexane concentration (∼10g chemical oxygen demand (COD)/L). Experimental results show that the inhibition of n-hexane on CH4 yield was negligible up to 2g COD/L and inhibition to methanogenesis became significant when it was higher than 4g COD/L based on quantitative mass balance. Inhibition threshold was about 4g COD/L of n-hexane. Analytical result of microbial community profile revealed that dominance of alkane-degrading sulfate-reducing bacteria (SRB) and syntrophic bacteria increased, while that of methanogens sharply dropped as n-hexane concentration increased. These findings offer a useful guideline of threshold n-hexane concentration and microbial community shift for the AD of lipid-extracted microalgal wastes.

Preparation of High-Purity Normal Hexane from Reformate Raffinate by Adsorption and Distillation Processes

In this study, a combination process of adsorption and distillation was adopted to obtain high-purity normal hexane. In the adsorption separation process, 5A zeolite was used as the adsorbent and the Shanghai Gaoqiao Petrochemical Corporation reformate raffinate containing 24.24 wt% normal hexane was separated into adsorption raffinate oil rich in non-normal paraffins and desorption oil rich in normal paraffins. At pre-specified operation conditions, concentration of n-hexane in the desorption oil reached higher than 96%. The concentrations of 3-methyl pentane and methyl cyclopentane, which are the light- and heavy-key components in the distillation tower of normal hexane, were reduced to 0.15% and 0.07%, respectively. According to the simulation results obtained using the software Aspen Plus, when the distillation tower has 15 stages, the n-hexane concentration can reach 99.02% with a recovery rate of 72.89% at the reflux ratio of 7.5. The combination process involving both adsorption and distillation ha...

Effects of Loading Type and Temperature on Performance, Transient Operation, and Kinetics of n-Hexane Vapor Removal in a Biofilter

In this research, different inlet concentrations of n-hexane vapor (1–11 g m−3) corresponds to the inlet loading rates of 9–598 g m−3 h−1 at different temperatures (35–45 °C) were eliminated from air under continuous and intermittent loading (10-h feeding per day) in a biofilter packed with compost and lava rock. Loading type had minor effect on the n-hexane removal at 35 °C and the removal efficiency (RE) was in the range of 70 to 100 % at an inlet concentration of 11 gm−3. On the contrary, RE dropped significantly to 25 % at 40 °C under intermittent loading while it was 77 % under continuous loading with the inlet concentration of 9 g m−3 and empty bed residence time (EBRT) of 2 min. Increasing the temperature to 45 °C significantly reduced the RE at both types of loading at both EBRTs of 2 and 1.3 min; however, intermittent loading was led to a slightly greater removal. According to transient-state experiment under intermittent loading at EBRT of 2 min, the biochemical reaction became the dominant mechanism, after an initial short period, every day to remove n-hexane rather than adsorption on bed. Kinetic modeling showed that the biodegradation rates changed linearly with increase in the logarithmic mean n-hexane concentration during intermittent loading at different temperatures while the order of reaction was higher at continuous loading.