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[en] Pretreatment of biosorbents have been suggested to modify the surface characteristics which could improve biosorption process. Stable cesium biosorption was studied in continuous fixed-bed column by chemically modified biosorbents. Two kinds of brown algae (Sargassum glaucescens and Cystoseira indica) were treated with chemical agents including formaldehyde (FA), glutaraldehyde (GA), potassium hexacyanoferrate (HCF), FA and HCF, and GA and HCF. The highest biosorption capacity (BC) was obtained from C. indica treated with FA (63.5 mg Cs/g biomass) and S. glaucescens treated with FA and HCF (62 mg Cs/g biomass). To study the effect of the best treatments on the BC, the concentration of each treatment agent was decreased. With decreasing FA agent for C. indica treatment, the BC dropped. Treatment of 1 g S. glaucescens biomass with 2.2 g FA and then 0.18 g HCF resulted in the highest BC (73.08 mg Cs/g dry biomass) which was 35.8 times higher than intact S. glaucescens
[en] Taguchi method was applied as an experimental design to determine optimum conditions for color removal from textile dyebath house effluents in a zeolite fixed bed reactor. After the parameters were determined to treat real textile wastewater, adsorption experiments were carried out. The breakthrough curves for adsorption studies were constructed under different conditions by plotting the normalized effluent color intensity (C/C0) versus time (min) or bed volumes (BV). The chosen experimental parameters and their ranges are: HTAB concentration (Chtab), 1-7.5 g L-1; HTAB feeding flowrate (Qhtab), 0.015-0.075 L min-1; textile wastewater flowrate (Qdye), 0.025-0.050 L min-1 and zeolite bed height (Hbed), 25-50 cm, respectively. Mixed orthogonal array L16 (42 x 22) for experimental plan and the larger the better response category were selected to determine the optimum conditions. The optimum conditions were found to be as follows: HTAB concentration (Chtab) = 1 g L-1, HTAB feeding flowrate (Qhtab) = 0.015 L min-1, textile wastewater flowrate (Qdye) = 0.025 L min-1 and bed height (Hbed) = 50 cm. Under these conditions, the treated wastewater volume reached a maximum while the bed volumes (BV) were about 217. While HTAB concentration, g L-1 (A); zeolite bed height, cm (D) and wastewater flowrate, L min-1 (C) were found to be significant parameters, respectively, whereas, HTAB flowrate, L min-1 (B) was found to be an insignificant parameter
[en] In this study, the ability of surfactant-modified zeolite (SMZ) to remove color from real textile wastewater was investigated. Tests were performed in a fixed-bed column reactor and the surface of natural zeolite was modified with a quaternary amine surfactant hexadecyltrimethylammonium bromide (HTAB). The zeolite bed that was modified at 1 g L-1 HTAB concentration and HTAB flow rate of 0.015 L min-1 showed good performance in removing color. Effects of wastewater color intensity, flow rates and bed heights were also studied. Wastewater was diluted several times in the ratios of 25%, 50% and 75% in order to assess the influence of wastewater strength. The breakthrough curves of the original and diluted wastewaters are dispersed due to the fact that breakthrough came late at lower color intensities and saturation of the bed appeared faster at higher color intensities. The column had a 3-cm diameter and four different bed heights of 12.5, 25, 37.5 and 50 cm, which treated 5.25, 19.50, 35.25 and 51 L original textile wastewater, respectively, at the breakthrough time at a flow rate of 0.025 L min-1. The theoretical service times evaluated from bed depth service time (BDST) approach for different column variables. The calculated and theoretical values of the exchange zone height were found with a difference of 27%. The various design parameters obtained from fixed-bed experimental studies showed good correlation with corresponding theoretical values, under different bed heights. The regeneration of the SMZ was also evaluated using a solution consisting of 30 g L-1 NaCl and 1.5 g L-1 NaOH at pH 12 and temperature 30 oC. Twice-regenerated SMZ showed the best performance compared with the others while first- and thrice-regenerated perform lower than the original SMZ.
[en] This paper describes the results of a study of the variation in the radial direction in the porosity of annular packed beds. A comparison is made between the predictions by a number of empirical correlations found in literature, the porosities obtained from physical experiments and the porosities obtained from the analysis of numerically generated packed beds. It is concluded that the numerical annular packed beds can be considered as acceptable representations of the actual annular packed beds. From the comparison between a number of exponential correlations proposed by various authors for the variation in the radial direction in the 'averaged' porosity and the numerical results it is recommended that the correlation proposed by Hunt and Tien be used to describe the variation in the radial direction in the porosity. It is, however, also recommended that a further thorough study be conducted to develop a more detailed understanding of the porosity characteristics of annular packed beds
[en] A new type of packed bed biofilm reactor was developed and research was started as a part of the new bioprocess system for anaerobic biofilm (BPSab). The present paper is dedicated to the investigations of the behavior of the new BPSab with this reactor as its major part. The new device passed a long period of incessant functioning under tough operational conditions. This was a good proof of the suitability of the new bioreactor as a laboratory tool for anaerobic biofilm investigations. It ensured stable experimental conditions for investigations of the influence on the intensity of mixing and the temperature on the BPSab productivity of biogas. Study of the mixing intensity on the bioreactor productivity showed an indifferent behavior to this factor in a rather large interval of changes of its values. As to the temperature, the reaction was similar to that of the chemical process systems following the Arrhenius rule in some part of the interval of its changes.
[en] Dynamic liquid holdup in a turbulent contact absorber was obtained through quick shut off valves technique. Experiments were carried out in a Perspex column. Effects of liquid velocity, gas velocity, packing diameter packing density and packing height on dynamic liquid holdup were studied. Hollow spherical high density polyethylene (HDPE) balls were used as inert fluidized packing. Experiments were performed at practical range of liquid and gas velocities. Holdup was calculated on the basis of static bed height. Liquid holdup increases with increasing both liquid and gas velocities both for type 1 and type 2 modes of fluidization. Liquid holdup increases with packing density. No effect of dia was observed on liquid holdup. (author)
[en] Highlights: • The effects of packing forms and particle shapes are investigated systematically. • Long ellipsoids have better performance in the SC and BCC packings. • FCC-L2 does not obtain lower reduced plate height than FCC-S. • Composite packings do not always have a good performance. • The unified equation form in ordered packed beds is proposed. - Abstract: Ordered structures are considered as the potential choice to improve the efficiency of separation. Moreover, the pore connectivity and pore size distribution of structured packed beds could be designed to improve the column separation performance. We have investigated the separation performance of different ordered packings in detail with the volume averaging method and numerical simulations, including simple cubic (SC), body center cubic (BCC), and face center cubic (FCC) packing with different particles. The effects of packing forms and particle shapes are discussed. Firstly, it is found that, the effects of packing forms and particle shapes on the plate height are remarkable. In the simple cubic packing, long ellipsoidal models have better separation performance and the channel effect makes molecular longitudinal diffusion insensitive to particle shapes. Secondly, with the same particle shape, the separation performance in the FCC packing is better. Compared with the corresponding configurations with spherical particles, the plate heights of long ellipsoidal particle models are remarkably reduced in the SC and BCC packing. Long ellipsoidal particles can enhance longitudinal diffusion obviously in the BCC and FCC packing. Thirdly, in the composite packing forms, the configurations with the same particles at the eight corners of the unit cell (BCC-S and BCC-S-S, BCC-L2 and BCC-L2-S) have the similar separation performance. Moreover, composite packings do not always improve separation performance. Finally, the unified equation form of separation performance is firstly proposed by the investigation of various ordered packed beds. By data fitting, the reduced longitudinal dispersion can be represented by the same power law pattern. Two velocity dependent factors consist of the same power law and fractional function form. These results provide more detailed flow characteristics and mass transfer process in ordered packed beds.
[en] The protonated Sargassum muticum seaweed was studied as a possible biosorbent for cadmium removal in a fixed-bed column. The experiments were conducted in order to determine the effect of flow rate (0.42, 5, 10 and 20 mL min-1) and bed height (0.6 and 15.3 cm for the lowest flow rate or 7.4, 13 and 16.6 cm for the others) on breakthrough curves behaviour. The determined breakthrough and exhaustion times increased with the diminution in flow rate and with the increase in bed height. The maximum cadmium uptake capacity, obtained from the area below adsorbed cadmium concentration versus time curves, was found to remain practically constant with bed depth and flow rate. The bed depth service time (BDST) model was applied to analyse experimental data, determining the characteristic process parameters. The optimal lowest sorbent usage rate was evaluated at 2 min contact time and the minimum bed height values necessaries to prevent the effluent solution concentration from exceeding 0.02 mg L-1 at zero time were 5.3, 6.9 and 7.5 cm for flow rates of 5, 10 and 20 mL min-1, respectively. Several empirical models proposed in the literature (Bohart-Adams, Yan, Belter and Chu models) were investigated in order to obtain the best fit of column data, describing in a simple manner the breakthrough curves. A correlation between model parameters and the variables implied in the process was attempted
[en] In this paper the production of laccase and the decolouration of the recalcitrant diazo dye Reactive Black 5 (RB5) by the white-rot fungus Trametes pubescens immobilised on stainless steel sponges in a fixed-bed reactor were studied. Laccase production was increased by 10-fold in the presence of RB5 and reached a maximum value of 1025 U/l. Enhanced laccase production in the presence of RB5 in this fungus is an added advantage during biodegradation of RB5-containing effluents. The decolouration of RB5 was due to two processes: dye adsorption onto the fungal mycelium and dye degradation by the laccase enzymes produced by the fungus. RB5 decolouration was performed during four successive batches obtaining high decolouration percentages (74%, 43% and 52% in 24 h for the first, third and four batch, respectively) without addition of redox mediators. Also, the in vitro decolouration of RB5 by the concentrated culture extract, containing mainly laccase, produced in the above bioreactor was studied. The decolouration percentages obtained were considerably lower (around 20% in 24 h) than that attained with the whole culture
[en] Bacterial strain Cr47 was isolated from a landfarming process soil sample. It was identified, by 16s rDNA sequencing, as Arthrobacter sp. The time course of the Cr(VI) reduction was monitored in batch operated packed bed biofilm reactors (12mL void volume) and in recirculating packed bed biofilm reactors (100 mL void volume) inoculated with bacterial strain Cr47. The reduction was evaluated with, 30 mg L-1 Cr(VI) laboratory solutions prepared with K2Cr2O7 and enriched with glucose-minimal medium, and with 30 mg L-1 Cr(VI) industrial model solutions prepared with chrome plating waste waters enriched with sucrose-minimal medium. Under batch mode the reduction reaction by the biofilm seemed to fit well an exponential-decay model with a first order kinetic parameter of 0.071 mg(L h)-1 Cr(VI). In the recirculating reactor, monitored after 4 weeks from inoculation and fed with laboratory solutions the removal rate was 0.79 mg(L h)-1. In the reactor fed with the industrial model solutions the maximum Cr(VI) removal rate attained was 0.49 mg(L h)-1. Artrobacter sp. packed bed biofilm reactors achieved Cr(VI) reduction rates comparable to other aerobic and anaerobic fixed film bioreactors previously reported