Height Of Mass Transfer Zone Research Articles

Montmorillonite impregnated electrospun cellulose acetate nanofiber sorptive membrane for ciprofloxacin removal from wastewater

The present study investigates the efficiency of electrospun montmorillonite-impregnated cellulose acetate nanofiber membranes (MMT-CA-NFM) for adsorptive removal of ciprofloxacin (CIP). Surface morphology, nanofiber characteristics and pHzpc of NFM were analysed by FE-SEM, EDS and pH drift method, respectively. The surface morphology of NFM showed random arrangements of nanofiber. Experiments were performed in batch mode to examine the effect of contact time, adsorbent dose, initial CIP concentration, pH, electrolyte, temperature and agitation speed. It was observed that 60 min contact was sufficient to reach reaction equilibrium and corresponding percentage removal was 76 % when CIP concentration, MMT-CA-NFM dose and solution pH were 10 mg/L, 4 g/L and 6.0 respectively. Equilibrium of the adsorption was described well by both Langmuir and Freundlich isotherm models. The sorption capacity was determined to be 13.8 mg/g. The sorption most closely followed Elovich kinetics model among the models tested. The pH range 6–7.5, where the zwitter ionic nature of CIP was dominant, was found to be most favourable for adsorption. Decrease of ΔG with increase in temperature demonstrated that CIP removal was favourable at higher temperature and positive values of ΔH confirmed endothermic nature of reaction. In continuous mode of operation using fixed bed column, the height of mass transfer zone was found to be 14.96 cm and adsorption rate and capacity constant in continuous mode were also calculated. The regeneration experiments indicated that 10 mM NaOH solution can desorb CIP from exhausted NFM and adsorbent demonstrated good reusability for removal of the antibiotic studied.

Microcolumn studies of dye biosorption from textile effluent on to dead biomass ofRhizopusarrhizusNCIM 997

Adsorption behavior of remazol reactive dyes from textile effluent was investigated using Rhizopus arrhizus as a biosorbent in up-flow fixed-bed micro column. The characteristics of mass transfer zone (MTZ), where adsorption in column occurs, were affected by bed depth and flow rate. The height of mass transfer zone (HMTZ), the rate of mass transfer zone (RMTZ), the effluent volume (Veff) and the column capacity at exhaustion (qcolumn) were estimated for the removal of dyes by the biosorbent. Thomas and Yoon–Nelson models were applied to the experimental data to predict the “S” shaped breakthrough curves and to determine the biosorption capacity of the column. Both the models were found suitable for describing the whole dynamic behavior of the column with respect to flow rate and bed depth. Hutchins BDST model showed that the variation of the service time with the bed depth was highly linear, thus, indicating its validity when applied to the continuous microcolumn studies. The empty bed residence time model (EBRT) indicated that the biosorbent exhaustion rate decreased with increasing EBRT. The results of this study indicated the applicability of fixed-bed micro column for removing remazol reactive dyes from the textile effluent. © 2017 American Institute of Chemical Engineers Environ Prog, 2017

Combination of adsorption-diffusion model with CFD for study of desulfurization in fixed bed

A 2D porous media Computational Fluid Dynamics (CFD) model is developed for a fixed bed adsorber to remove the 4,6-dimethyldibenzothiophene (4,6-DMDBT) from diesel. The Ag-TiO2-SiO2 modified by CeOx adsorbent is used to remove the 4,6-DMDBT from diesel and proves that CeOx species could promote high dispersion of Ag species on adsorbent surface. The mass source term describing mass transfer of 4,6-DMDBT inside the adsorption bed column is considered. The effects of various parameters such as feed concentration, feed rate and column height on adsorption process have been investigated. Mesh independent test is performed to investigate the effect of the grid size on the simulation results. The component distribution contour and mass transfer rate are employed to analyse further the mass transfer phenomenon in fixed bed column. The higher mass transfer rate at the beginning can be observed and the lower mass transfer rate is obtained after a period of adsorption time at high feed concentration. Results also demonstrate that the porous media CFD model can successfully describe the adsorption of 4,6-DMDBT from diesel in fixed bed column. Finally, the results of Genetic algorithm search suggest that the optimal height of mass transfer zone can be got at low feed rate, high bed height and low feed concentration.

Composite of biomass and lead resistent Aspergillus oryzae for highly efficient aqueous phase Pb(II) adsorption

In this research, compound biosorbent peanut shell‐HA (PSH) and millet chaff‐HA (MCH), which were composited by peanut shell (PS) and millet chaff (MC) with lead resistent Aspergillus oryzae (HA), respectively, were used to remove Pb2+ from aqueous solution. The characterize of biosorbents were analyzed by FTIR and SEM. Batch experiments were performed to evaluate the effect of pH, biosorbent concentration, initial Pb2+ concentration and contact time on the Pb2+ removal. The results indicated that the functional groups and surface morphology of PSH and MCH were significantly different after compound procedures. The maximum adsorption capacity qm of PSH and MCH were 43.09% and 83.21% higher than PS and MC, respectively. Meanwhile, the compound biosorbent showed a significant adsorption advantage at the low pH and more efficient in adsorption compared to pristine materials. The adsorption isotherms and kinetics studies demonstrated that the adsorption process can be well fitted by the Langmuir and pseudo‐second‐order model, respectively. Fixed‐bed experiments showed that the MCH possesses stronger fixed bed adsorption capacity (qexp[MCH]=8.30 mg g−1,qexp[PSH]=7.13 mg g−1) and shorter height of mass transfer zone (H[MCH]=6.96 cm, H[PSH]=16.56 cm) than PSH. The compound biosorbents performs better than pristine materials with higher adsorption capacity. This study provides a promising strategy for manufacture of new biosorbent. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1658–1666, 2017

Batch and chromatographic removal of Nd3+ and Dy3+ ions from waste solutions using humic acid

Removal of Nd3+ and Dy3+Lanthanide metal ions from waste solutions using Giza Zoo humic acid (GZHA) was studied by batch and chromatographic column experiments. The results of batch experiments demonstrated that maximum removal of both Nd3+ and Dy3+were 753.75 and 667.97mg/g from 10−2M HCl waste solutions at pH 2.0, 323±1K by GZHA, respectively, which are the highest values of GZHA compared with more than resent 25 adsorbents. Removal data were better described by Langmuir isotherm, while kinetics data were well fitted to pseudo second order model. Thermodynamic studies showed that the removal of both Nd3+ and Dy3+ions using GZHA is spontaneous, favorable and endothermic reactions.The value of activation energy (Ea) for Nd3+ and Dy3+ is 11.40 and 8.19kJ/mol, respectively suggests that the removal of both ion metals onto GZHA from waste solution under the applied experimental contion is a physicosorption process.The equilibrium removal capacity of the column ranged from 19.4 to 19.48 and 18.3 to 39.1mg/g for Nd3+ and Dy3+, respectively. The height of mass transfer zone increased with the increase in the initial concentration of influents; hz is 1.8, 2.4 and 3.3cm for Nd3+and 1.5, 2.1 and 3.6cm for Dy3+ at 50, 100 and 300mg/L, respectively. The efficiency of removal column for both Dy3+and Nd3+ is 85.4% and 77.2% at room temperature and 50mg/L influent concentration, respectively.

Removal of dissolved organic carbon by aquifer material: Correlations between column parameters, sorption isotherms and octanol-water partition coefficient

The correlation between octanol-water partition coefficient (KOW) and the transport of aqueous samples containing single organic compound is well documented. The concept of the KOW of river water containing the mixture of organics was evolved by Pradhan et al. (2015). The present study aims at determining the KOW and sorption parameters of synthetic aqueous samples and river water to finding out the correlation, if any. The laboratory scale columns packed with aquifer materials were fed with synthetic and river water samples. Under the operating conditions, the compounds in the samples did not separate, and all the samples that contain more than one organic compound yielded a single breakthrough curve. Breakthrough curves simulated from sorption isotherms were compared with those from the column runs. The sorption parameters such as retardation factor (Rf), height of mass transfer zone (HMTZ), rate of mass transfer zone (RMTZ), breakpoint column capacity (qb) and maximum column capacity (qx) estimated from column runs, sorption isotherms and models developed by Yoon-Nelson, Bohart-Adam and Thomas were in agreement. The empirical correlations were found between the KOW and sorption parameters. The transport of the organics measured as dissolved organic carbon (DOC) through the aquifer can be predicted from the KOW of the river water and other water samples. The novelty of the study is to measure KOW and to envisage the fate of the DOC of the river water, particularly during riverbank filtration. Statistical analysis of the results revealed a fair agreement between the observed and computed values.

Analysis and modeling of fixed bed sorption of cesium by AMP-PAN

Cesium sorption on ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) from simulated acidic waste was investigated in a fixed-bed column. Batch equilibrium isotherm data were tested with Freundlich and Langmuir models and both were found to fit the sorption isotherm data well, but the Langmuir model was better. Cesium exchange on AMP-PAN followed pseudo second-order kinetics. The effects of influent Cs concentration (500–1000mg/L), feed flow rate (5–15mL/min) and bed height (14.5–21.5cm) on the breakthrough characteristics of the ion-exchange system were determined. The uptake capacity increased with increase in initial ion concentration and bed height but decreased with increase in flow rate. Breakthrough occurred earlier for higher concentrations, higher flow rates and lower bed heights. The dynamics of the mass transfer zone were described for different column operating conditions. The height of mass transfer zone decreased with increase in initial concentration and increased with increase in flow rate. No significant effect was observed in the height of mass transfer zone with increase in height of bed. Mathematical models of Thomas, Yoon–Nelson and Bohart–Adams model were applied to the experimental data to analyze the column performance. The results fitted well to the Thomas and Yoon–Nelson models with correlation coefficient, R2≥0.98.

Effect on mass transference phenomena by textural change inside monolithic carbon aerogels

The effects on mass transference phenomena due textural changes of monolithic carbon aerogels were studied by hexane adsorption. The monolithic carbon aerogels were prepared after carbonization of the organic aerogels obtained by resorcinol–formaldehyde polymerization, using p-toluenesulfonic acid (acid-catalyst) and sodium carbonate catalysts (basic-catalyst). Internal texture was modified by CO2 activation. The characterization by gas adsorption showed that the monolithic carbon aerogels presents a bi-modal pore size distribution with presence of both microporous and mesoporous. It was shown that the activation process of monolithic carbon aerogels increases their micropore volume bigger than the other one acid-catalyst aerogel. The mesopores volume in the carbon aerogels plays an important role on mass transport mechanism. The samples with presence of significant mesopore volume present a lower height of mass transfer zone than others less mesopore volume; therefore better efficiency of adsorption in mass transfer zone in dynamic adsorption. The breakthrough curve methodology proposed in this work has allowed finding a relationship between the structural parameters and dynamic adsorption variables, which opens new approaches for measuring textural parameters of material.

Adsorption characteristics of reactive dyes in columns of activated carbon

Adsorption behaviour of reactive dyes in fixed-bed adsorber was evaluated in this work. The characteristics of mass transfer zone (MTZ), where adsorption in column occurs, were affected by carbon bed depth and influent dye concentration. The working lifetime ( t x ) of MTZ, the height of mass transfer zone (HMTZ), the rate of mass transfer zone (RMTZ), and the column capacity at exhaustion ( q column) were estimated for the removal of remazol reactive yellow and remazol reactive black by carbon adsorber. The results showed that column capacity calculated at 90% of column exhaustion was lower than carbon capacity obtained from equilibrium studies. This indicated that the capacity of activated carbon was not fully utilized in the fixed-bed adsorber. The bed-depth service time model (BDST) was applied for analysis of reactive yellow adsorption in the column. The adsorption capacity of reactive yellow calculated at 50% breakthrough point ( N 0) was found to be 0.1 kg kg −1 and this value is equivalent to about 14% of the available carbon capacity. The results of this study indicated the applicability of fixed-bed adsorber for removing remazol reactive yellow from solution.

Removal of methylene blue by carbons derived from peach stones by H 3PO 4 activation: Batch and column studies

Several activated carbons were obtained by H 3PO 4 at 500 °C, under increasing acid concentrations of 30–70%. Products were characterized by N 2 at 77 K, and proved to be highly microporous with high surface area and pore volume that increased with impregnation ratio. Two modified carbons were prepared by concurrently passing N 2 during pyrolysis of impregnated precursor with 50% H 3PO 4 at 500 °C, and post-heat treatment at 800 °C for one carbon. A low reduction in porosity accompanied this treatment. Equilibrium adsorption of methylene blue (MB) proved good uptake of the bulky dye, which improved considerably with impregnant concentration that was related to enhanced porosity. Dynamic removal of MB was carried out by running solutions of influent concentrations, of 100–200 mg/L, through a mini-column. Many column performance parameters were estimated at different stages on the typical S-shaped breakthrough curves: volume treated, amounts uptaken, bed service time, height of mass transfer zone, and column exhaustion characteristics. Increased impregnation ratio improved column performance, as well as forcing N 2 pyrolysis or extra heat-treatment. Activated carbon impregnated with 70% H 3PO 4 and carbonized at 500 °C exhibited the best properties which prevailed upon raising treated dye concentration to 150 and 200 mg/L, although degraded its capacity due to the limited mass of adsorbent and to the short contact time.