Kinetics of the removal of mono-chlorobenzene vapour from waste gases using a trickle bed air biofilter

The performance of a trickle bed air biofilter (TBAB) in the removal of mono-chlorobenzene (MCB) was evaluated in concentrations varying from 0.133 to 7.187 g m(-3) and at empty bed residence time (EBRT) varying from 37.7 to 188.52 s. More than 90% removal efficiency in the trickle bed air biofilter was achieved for the inlet MCB concentration up to 1.069 g m(-3) and EBRT less than 94.26 s. The trickle bed air biofilter was constructed with coal packing material, inoculated with a mixed consortium of activated sludge obtained from sewage treatment plant. The continuous performance of the removal of MCB in the trickle bed air biofilter was monitored for various gas concentrations, gas flow rates, and empty bed residence time. The experiment was conducted for a period of 75 days. The trickle bed air biofilter degrading MCB with an average elimination capacity of 80 g m(-3) h(-1) was obtained. The effect of starvation was also studied. After starvation period of 8 days, the degradation was low but recovered within a short period of time. Using macrokinetic determination method, the Michaelis-Menten kinetic constant K(m) and maximum reaction rate, r(max) evaluated as 0.121 g m(-3) s(-1) and 7.45 g m(-3), respectively.     

Evaluation of trickle-bed air biofilter performance for MEK removal

A lab-scale trickle-bed air biofilter (TBAB) was operated to evaluate the removal of methyl ethyl ketone (MEK) from waste gas. Three biomass control strategies were investigated, namely, backwashing and two non-use periods (starvation and stagnant). Five volumetric loading rates from 0.70 to 7.04 kg COD/m(3)day were employed. Backwashing once a week removed the excess biomass and obtained long-term, stable performance over 99% removal efficiency for loading rates less than 5.63 kg COD/m(3)day. The two non-use periods could also sustain 99% removal efficiency and could be employed as another means of biomass control for loading rates up to 3.52 kg COD/m(3)day. The non-use periods did not delay the recovery when the loading rate did not exceed 3.52 kg COD/m(3)day. The pseudo-first-order removal rate constant decreased with increase in volumetric loading rate. The effect of non-use periods on removal rate showed apparent transition from positive to negative with the increase in loading rate.     

Removal of p-xylene from an air stream in a hybrid biofilter

Biofiltration of an air stream containing p-xylene has been studied in a laboratory hybrid biofilter packed with a mixture of mature pig compost, forest soil and the packing material which was made of polyethylene (PE) and used in the moving bed biological reactor (MBBR) in wastewater treatment. Three flow rates, 9.17, 19.87 and 40.66 m(3)m(-2)h(-1), were investigated for p-xylene inlet concentration ranging from 0.1 to 3.3 g m(-3). A high elimination capacity of 80 g m(-3)h(-1) corresponding to removal efficiency of 96% was obtained at a flow rate of 9.17 m(3)m(-2)h(-1) (empty bed residence time of 132 s). At a flow rate of 40.66 m(3)m(-2)h(-1) (empty bed residence time of 30s), the maximum elimination capacity for p-xylene was 40 g m(-3)h(-1) and removal efficiencies were in the range of 47-100%. The production of carbon dioxide (P(CO(2))) is proportional to elimination capacity (EC) and the linear relation was formulated as P(CO(2))=1.65EC+15.58. Stable pH values ranging from 6.3 to 7.6 and low pressure drop values less than 0.2 cm H(2)O (19.6 Pa) of packing media in compost-based biofilter of hybrid biofilter were observed, which avoided acidification and compaction of packing media and sustained the activity of microorganism populations.     

Removal of acrolein vapor from air by a nanosecond electron beam

Results are presented of an experimental investigation of the decomposition of small quantities of acrolein vapor in air irradiated by a pulsed electron beam. It is shown that the reduction in the impurity concentration as a function of the energy deposited in the gas is satisfactorily approximated by an exponential law. An empirical expression is derived to predict the energy consumption for a given initial acrolein concentration and required degree of purification. Pis’ma Zh. Tekh. Fiz. 24, 35–39 (August 26, 1998)     

Streamer corona removes styrene vapor from air flow

Decomposition of the styrene vapor in air induced by a 60-ns pulsed streamer corona discharge was studied. Empirical relationships were obtained that allow the necessary energy consumption to be evaluated depending on the required degree of purification, the initial styrene content in air, and the nitrogen-oxygen mixture composition. On this basis, a general equation is derived that provides systematization of the experience in air purification.     

Removal of ozone from air by activated carbon treatment

Removal of ozone from air was investigated by using regular and surface modified activated carbons. The modified carbons were prepared by impregnating granular activated carbon or activated carbon fiber with metal salts, and by molding coconut-based activated carbon powder with compounds such as CuCl₂ or KNO₃ and binders. A flow method was used in the measurements, and effluent air was analyzed to determine the extent of ozone removal. Mechanism of ozone decomposition was inferred from changes of the concentrations of surface functional groups, the pore volume, and the amount of unpaired electron of adsorbents before and after ozone treatment. Furthermore, desorption of oxygen molecule and the irreversibly adsorbed ozone molecules was studied by a thermal-programmed desorption method. Partial decomposition of ozone in carbon beds was shown to be present from the measurement of the amount of unpaired electron and the reaction of carbon with ozone was found to be of a half order.     

Chemical vapor deposition of refractory metals from fluoride gases

The kinetics of the chemical vapor deposition of Group V (V, Nb, Ta), VI (Mo, W), and VII (Re) transition metals from fluoride-hydrogen mixtures were studied. The major steps of the deposition process were established. The deposition rate is shown to correlate with the thermodynamic probability of hydrogen reduction. The effect of intermediate products on the deposition rate of 3d and 4d transition metals is assessed.     

Removal of cadmium from aqueous solutions by adsorption onto orange waste

The use of orange wastes, generated in the orange juice industry, for removing cadmium from aqueous solutions has been investigated. The material was characterized by Fourier transform infrared spectroscopy and batch experiments were conducted to determine the adsorption capacity of the biomass. A strong dependence of the adsorption capacity on pH was observed, the capacity increasing as pH value rose. Kinetics and adsorption equilibrium were studied at different pH values (4-6). The adsorption process was quick and the equilibrium was attained within 3h. The maximum adsorption capacity of orange waste was found to be 0.40, 0.41 and 0.43 mmol/g at pH 4-6, respectively. The kinetic data were analysed using various kinetic models - pseudo-first order equation, pseudo-second order equation, Elovich equation and intraparticle diffusion equation - and the equilibrium data were tested using four isotherm models - Langmuir, Freundlich, Sips and Redlich-Peterson. The data were fitted by non-linear regression and five error analysis methods were used to evaluate the goodness of the fit. The Elovich equation provides the greatest accuracy for the kinetic data and the Sips model the closest fit for the equilibrium data.     

Removal of hexavalent chromium from aqueous solution by agricultural waste biomass

In the present study adsorption of Cr(VI) from aqueous solutions onto different agricultural wastes, viz., sugarcane bagasse, maize corn cob and Jatropha oil cake under various experimental conditions has been studied. Effects of adsorbent dosage, Cr(VI) concentration, pH and contact time on the adsorption of hexavalent chromium were investigated. The concentration of chromium in the test solution was determined spectrophotometrically. FT-IR spectra of the adsorbents (before use and after exhaustion) were recorded to explore number and position of the functional groups available for the binding of chromium ions on to studied adsorbents. SEMs of the adsorbents were recorded to explore the morphology of the studied adsorbents. Maximum adsorption was observed in the acidic medium at pH 2 with a contact time of 60min at 250rpm stirring speed. Jatropha oil cake had better adsorption capacity than sugarcane bagasse and maize corn cob under identical experimental conditions. The applicability of the Langmuir and Freundlich adsorption isotherms was tested. The results showed that studied adsorbents can be an attractive low cost alternative for the treatment of wastewaters in batched or stirred mode reactors containing lower concentrations of chromium.     

胶团强化超滤处理含镉废水

采用聚砜中空纤维超滤膜,十二烷基硫酸钠为表面活性剂,对含镉废水进行胶团强化超滤．研究了运行时间、十二烷基硫酸钠(SDS)浓度、膜操作压力、溶液pH、溶液中电解质浓度、与非离子表面活性剂Brij复配等因素对该工艺的影响．结果表明,该工艺对镉的去除率可达99％以上．但该工艺不适用于强酸性废水,电解质的存在会降低截留率,SDS与Brij复配能提高截留率．     

Diffusion of mercury vapor in gases

The results of experimental investigation of diffusion of the vapor of mercury and other metals in gases and a correlation of the data are given.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 3, pp. 495–500, September, 1977.     

废旧聚苯乙烯制备水溶性带锈涂料

采用混合溶剂将废聚苯乙烯泡沫塑料进行溶解 ,并选用改性剂和引发剂进行共聚接枝 ,再与铁锈转化剂和分散添加剂复配制得无污染的带锈防锈涂料。     

Removal of hazardous dye congored from waste material

The present paper is aimed to investigate and develop cheap adsorption methods for color removal from wastewater using waste material sawdust as adsorbent. Sawdust, a biosorbent, was successfully utilized in removing a water soluble azo dye, congored from wastewater. The paper incorporates effect of pH, temperature, amount of adsorbent, contact time, concentration of adsorbate, particle size on adsorption. Specific rate constants of the processes were calculated by kinetic measurements and a first order adsorption kinetics was observed in each case. Langmuir and Freundlich adsorption isotherm models were then applied to calculate thermodynamics parameters as well as to suggest the plausible mechanism of the ongoing adsorption processes. In order to observe the quality of wastewater COD measurements were also carried out before and after the treatments. A significant decrease in the COD values was observed, which clearly indicates that adsorption method offer good potential to remove congored from wastewater.     

Removal of oil from stable oil-water emulsion by induced air flotation technique

The present study investigates the application of induced air flotation technique on oil removal performance of a separator column (d = 10 cm; H = 150 cm). A preparation method to produce a very stable synthetic emulsion was developed. The stability rate constants K_st were determined under different conditions, and K_st for very stable emulsion was 0.000907 h ⁻¹. Several parameters affecting the performance of the separator were investigated. The experimental data were also analyzed in terms of a first-order kinetic rate model. A removal rate constant, K_r, was obtained. The maximum oil removal obtained from stable emulsion contained 4% by weight sodium chloride was 78.1%, and the corresponding K_r value was 9.18 h⁻¹.     

Effect of shutdown on styrene removal in a biofilter inoculated with Pseudomonas sp. SR-5

Styrene gas removal was carried out in a biofilter inoculated with a styrene-degrading Pseudomonas sp. SR-5 using a mixed packing material of peat and ceramic under the non-sterile condition. More than 86% removal efficiency was obtained at styrene load of 5-93 g m(-3) h(-1) for 62 days operation period and 78% carbon of removed styrene was converted to CO2. Thereafter, three kinds of styrene shutdown experiments were conducted: (i) air and mineral medium were supplied for 4 days, (ii) complete shutdown, namely no styrene, air and moisture supply was conducted for 3 days, and (iii) only air was supplied for 11 days. When styrene gas was re-supplied after (i) and (iii) shutdown experiments, styrene removal efficiency rapidly recovered, but after (ii) shutdown, recovery of styrene removal was significantly delayed. Supply of air during shutdown period was found to be enough to resume microbial activity to degrade styrene.