Length Of Mass Transfer Zone Research Articles

Comparison of upward and downward flow in high-pressure bulk CO2 gas adsorption on NaY zeolite fixed bed

Adsorption is an appealing technology for the removing of CO2 from natural gas because it can handle high CO2 concentrations at high pressures. The determination of mono-component breakthrough curves provides heat and mass transfer parameters to assess separation effectiveness that can be used for simulation of swing adsorption separation processes (PSA, TSA etc.). However, in lab-scale fixed-bed adsorption, it may be challenging to perform this assessment due to low flow conditions that are usually employed, affecting the flow regimedepending on the operation conditions. In this sense, this work aimed to evaluate the effect of flow regime configurations and difference in gases densities by means of residence time distribution (RTD) analysis in the PSA of CO2 in a NaY zeolite fixed bed , in order to to collect information that satisfy pipeline specifications in industrial applications. A high-pressure lab-scale apparatus was used with NaY particles of 0.7250 mm mean diameter, a 10.5 cm bed height , and a tubular column of 2.0 cm internal diameter. The upward and downward flows were conducted under 528.82 ± 4.59 NmL min−1 inlet mass flow rate, 51 bar, and 30 °C. The RTD analysis was performed to verify the flow regime, and mass transfer zone (MTZ) length was estimated. It was observed that downward flow conditions promoted higher concentration spread than upward flow. RTD analysis showed that downward flow is dominated by laminar convection while the upward flow is dominated by dispersion. MTZ length increased from 0.64 cm in upward flow to 5.81 cm in downward flow. Therefore, assessing CO2 flow conditions and, additionally, the difference in gases densities, are important steps that should be taken when dealing with fluid adsorption under high pressure because different densities between fluid components severely changed and affected flow regime and, consequently, separation effectiveness.

Efficient removal of environmentally hazardous heavy metal ions from water by NH2-MIL-101-Fe and MOF-808-EDTA based polyether sulfone adsorbents

The potential of metal–organic frameworks (MOFs) based polymeric composites for heavy metal removal was analyzed in this study. Two mixed matrix composites, along with NH2-MIL-101-Fe and MOF-808-EDTA, were synthesized. The MOFs were synthesized using the solvothermal method, and the mixed matrix spheres (MMSs) were prepared using the facile dropping method. The MMSs were characterized, and batch adsorption studies were performed at different pH and adsorbent dosages. For both MMSs, the optimum pH was between 5–5.5, and the highest removal rates were obtained for MOF-808-EDTA spheres (94 % Hg2+, 86 % As, 80 % Mn). The optimum adsorbent dosage for MOF-808-EDTA was found to be 5.42 g/L, while for NH2-MIL-101-Fe, it was 7.13 g/L, after which the metal ion removal efficiency was reduced. Langmuir adsorption isotherm was fitted with thermodynamic evaluation of Gibbs free energy, enthalpy, and entropy. MOF-808-EDTA demonstrated a greater adsorption capacity of 272.7 mg/g (Hg2+), 151.29 mg/g (As3+), and 125.9 mg/g (Mn2+) than the other MMP. The Gibbs free energy of −20.14 (Hg2+), −12.66 (Mn2+), and −52.61 kJ/mol (As3+) were obtained from the thermodynamic study. The results indicated that the process was exothermic and spontaneous. Breakthrough column studies were performed for MOF-808-EDTA spheres using the pore-surface-diffusion model. The transient column study was conducted for individual heavy metal ion solutions using Addesign™ software to evaluate column exhaustion time, breakthrough time and length of mass transfer zone. Studies with multicomponent solutions of heavy metals also gave potentially promising results in the separation of 92 % of Hg, 84 % As, and 75 % Mn which indicates the prepared adsorbents can be used to remove heavy metal ions from industrial wastewater samples.

Removal of protein wastes by amidoximated polyacrylonitrile nanofiber membrane decorated with dye wastes in batch and flow modes

Amidoximated polyacrylonitrile nanofiber membranes (P-Oxime) were functionalized with a reactive green 19 (RG19, as a model dye waste), to remove lysozyme as a soluble microbial protein model. The P-Oxime-RG19 nanofiber membranes were applied to remove lysozyme in batch and flow modes. The most effective removal capacity of P-Oxime-RG19 nanofiber membranes for lysozyme in batch mode was 1126.37 mg/g. The performance of P-Oxime-RG19 nanofiber membranes for removal of lysozyme in flow mode was further investigated under different pH values, loading flow rates, and loading concentrations of lysozyme. The influences of process parameters on the shape of the breakthrough curve were analyzed, and the experimental results were fitted with various dynamic models to understand the removal behavior of P-Oxime-RG19 nanofiber membranes. The results illuminated the substantial variations in the dynamic binding characteristics of P-Oxime-RG19 nanofiber membranes, including breakthrough time, dynamic binding capacity, mass transfer zone length, and membrane bed utilization. The adsorbed lysozyme could be completely washed out from the dyed membrane using 1.5 M NaCl.

Conversion of foliar residues of Sansevieria trifasciata into adsorbents: dye adsorption in continuous and discontinuous systems.

The study analyzed the potential of leaf powder prepared from the residual leaves of the species Sansevieria trifasciata, as a potential adsorbent for methylene blue (MB) removal. The equilibrium was reached fast for almost all concentrations after 60min, obtaining the maximum capacity of 139.98mgg-1 for 200mg L-1. The increase in temperature disfavored the dye adsorption, with the maximum adsorption capacity of 225.8mgg-1, observed for 298K. The thermodynamic parameters confirmed that the adsorption process is spontaneous and exothermic. A direct sloping curve was established for the fixed bed, with breakthrough time (tb), column stoichiometric capacities (qeq), and the mass transfer zone lengths (Zm) were 1430, 1130, and 525min; 60.48, 187.01, and 322.65mgg-1; and 8.81, 11.28, and 10.71cm, for 100, 200, and 500mg L-1, respectively. Furthermore, in a mixture of several dyes, the adsorbent obtained the removal of 51% of the color.

Heterogeneous catalytic degradation of dye by Fenton-like oxidation over a continuous system based on Box–Behnken design and traditional batch experiments

In this study, iron was coupled with copper to form a bimetallic compound through a biosynthetic method, which was then used as a catalyst in the Fenton-like processes for removing direct Blue 15 dye (DB15) from aqueous solution. Characterization techniques were applied on the resultant nanoparticles such as SEM, BET, EDAX, FT-IR, XRD, and zeta potential. Specifically, the rounded and shaped as spherical nanoparticles were found for green synthesized iron/copper nanoparticles (G-Fe/Cu NPs) with the size ranging from 32-59 nm, and the surface area was 4.452 m2/g. The effect of different experimental factors was studied in both batch and continuous experiments. These factors were H2O2 concentration, G-Fe/Cu-NPs amount, pH, initial DB15 concentration, and temperature in the batch system. The batch results showed 98% of 100 mg/L of DB15 was degraded with optimum H2O2 concentration, G-Fe/Cu-NPs dose, pH, and temperature 3.52 mmol/L, 0.7 g/L, 3, and 50℃ respectively. For the continuous mode, the influences of initial DB15 concentration, feed flow rate, G-Fe/Cu-NPs depth were investigated using an optimized experimental Box-Behnken design, while the conditions of pH and H2O2 concentration were based on the best value found in the batch experiments. The model optimization was set the parameters at 2.134 ml/min flow rate, 26.16 mg/L initial dye concentration, and 1.42 cm catalyst depth. All the parameters of the breakthrough curve were also studied in this study including break time, saturation time, length of mass transfer zone, the volume of bed, and volume effluent.

Fixed-Bed Adsorption of Lead from Aqueous Solution Using Chitosan-Coated Bentonite.

In this study, fixed-bed adsorption of Pb(II) from an aqueous solution using chitosan-coated bentonite (CCB) was investigated. Characterization of CCB was performed using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The effects of varying bed height (1.3 to 4.3 cm), flow rate (0.20 to 0.60 mL/min), and initial concentration (500 to 1500 mg/L) on the length of mass transfer zone (Zm) and adsorption capacity at breakthrough (qb) and exhaustion (qe) were examined. Low flow rate and high bed height were determined to cause a longer time to reach breakthrough and exhaustion. Meanwhile, the fixed-bed system was observed to quickly attain breakthrough and exhaustion under high initial concentrations. Kinetic column models such as the Thomas, Yoon–Nelson, and Clark models were used to predict the breakthrough curves. High R2 values (0.9758 ≤ R2 ≤ 0.8087) were attained for the Thomas model, which indicates that there is good agreement between experimental data and linear plots generated by the Thomas model. Moreover, the Thomas model is best in describing the breakthrough curves of Pb(II) removal under a fixed-bed system.

Comparative Study of CO2 Capture by Adsorption in Sustainable Date Pits-Derived Porous Activated Carbon and Molecular Sieve.

The rising CO2 concentration has prompted the quest of innovative tools to reduce its effect on the environment. A comparative adsorption study using sustainable low-cost date pits-derived activated carbon and molecular sieve has been carried out for CO2 separation. The adsorb ents were characterized for surface area and morphological properties. The outcomes of flow rate, temperature and initial adsorbate concentration on adsorption performance were examined. The process effectiveness was investigated by breakthrough time, adsorbate loading, efficiency, utilized bed height, mass transfer zone and utilization factor. The immensely steep adsorption response curves demonstrate acceptable utilization of adsorbent capability under breakthrough condition. The adsorbate loading 73.08 mg/g is achieved with an 0.938 column efficiency for developed porous activated carbon at 298 K. The reduced 1.20 cm length of mass transfer zone with enhanced capacity utilization factor equal 0.97 at 298 K with Cin = 5% signifies better adsorption performance for date pits-derived adsorbent. The findings recommend that produced activated carbon is greatly promising to adsorb CO2 in fixed bed column under continuous mode.

Continuous fixed-bed column study for removal of Congo red dye from aqueous solutions using Nelumbo nucifera leaf adsorbent

ABSTRACT The adsorption of Congo red (CR) dye from aqueous solutions is conducted in a continuous fixed-bed column by using agricultural biomass of Nelumbo nucifera leaf adsorbent. The column performance is evaluated by varying the adsorbent bed height (2.5‒5 cm), influent dye concentrations (10–50 mg L−1), and inlet flow rate (1‒5 mL min−1). Column experimental data confirmed that the breakthrough characteristics of the adsorption system are dependent on bed height, flow rate, and initial adsorbate concentration. The results show that the decolourisation efficiency and equilibrium uptake (qe) of CR decreases with increasing flow rate and increases with increasing bed height and influent adsorbate concentration. The maximum absorption efficiency (83.12%) was obtained using 5 cm bed height, 15 mg L−1 inlet adsorbate concentration, and 1 mL min−1 flow rate. The increased flow rate and initial adsorbate concentration lead to a shorter column exhaustion time. The length of mass transfer zone increased with increasing bed height. Various mathematical models are applied to column experimental data to predict the breakthrough curve and to evaluate the column capacity and kinetic constants of the models. The correlation between the experimental and theoretical data is quantified by calculating the regression coefficients for the Thomas and Yoon–Nelson models, an R 2 ≥ 0.954 at various operating conditions was obtained, which shows that the trend of experimental data fits well and the overall system kinetics are limited by solid-liquid interphase mass transfer. The N. nucifera leaf fine powder adsorbent is proven to be capable of removing CR efficiently from aqueous solutions in continuous fixed-bed systems at low flow rate and higher bed depth and it can be used effectively in wastewater treatment.

CO2 capture using activated carbon synthesized from date stone: breakthrough, equilibrium, and mass-transfer zone

Global warming and climate changes are the ultimate consequences of increased CO2 volume in the air. Physical activation was used to prepare high-throughput activated carbon from a low-cost date stone. The adsorption performance of activated carbon using fixed bed for CO2 separation was studied. The reliance of temperature, flow rate, and initial CO2 concentration levels on breakthrough behaviour was analysed. The adsorption response was explored in terms of breakthrough and saturation points, adsorption capacity, temperature profiles, utilization factor, and length of mass-transfer zone. Increased temperatures lead to vary the breakthrough periods notably. The vastly steep breakthrough curves reveal satisfactory utilization of bed capacity. LMTZ is varied positively with increased feed rates and temperatures. The high utilization factor of 0.9738 with 1.66 mmol/g CO2 uptake was acquired at 298 K and 0.25 bars. The findings recommend that the carbon prepared from date stone is encouraging to capture CO2 from CO2/N2 mixture.

Packed bed column adsorption of phenol onto corn cob activated carbon: linear and nonlinear kinetics modeling

In the present study, linear and nonlinear regression analysis for packed bed column adsorption of phenol onto corn cob activated carbon was investigated. The activation of the corn cob provided the activated carbon with enhanced surface area and micropore volume of 903.7 m2/g and 0.389 cm3/g respectively. The analysis of the physical properties of the corn cob activated carbon (CCAC) revealed that it contained 33.47% of fixed carbon, 5.82% of ash content, 18.01% of volatile matter, 0.63 g/mL of bulk density, 5.50% of moisture content, and a pH of 6.30. SEM images indicated the presence of interspatial pores within the matrix of the adsorbent, while the FTIR analysis revealed that the major functional groups in CCAC were alkanol, alkanes, alkyls, carboxylic acids, ethers, esters, and nitro compounds. The effect of the process parameters influencing the dynamic adsorption process was investigated at flow rates (9–18 mg/min), initial phenol concentration (100-300 mg/L), bed height (5–10 cm), and particle size (300-800 µm). The breakthrough time and adsorption capacity increased with an increase in bed height but decreased with an increase in flow rate, initial phenol concentration, and particle size. At optimum conditions of bed height 10 cm, initial phenol concentration, 100 mg/L, flow rate, 9 mL/min, and particle size 300 µm, the adsorption capacity at breakthrough (qb), adsorption capacity at saturation (qs), volume of effluent treated at saturation (Veff,s), length of mass transfer zone (MTZ), adsorbent exhaustion rate (AER), fractional bed utilization (FBU) factor, Reynolds number (Re), Sherwood number (Sh), and the percentage phenol removal (Ys) were 2.143 mg/g, 8.570 mg/g, 12.96 L, 7.50 cm, 30.86 g/L, 0.25, 17.93, 28.85, and 66.13% respectively. The linear and nonlinear regression analysis of the Thomas, Adams-Bohart, and Wolborska models fitted better with the experimental data than the Yoon–Nelson model. Generally, the nonlinear regression proved to be a better tool for dynamic adsorption model analysis as the model parameters generated by the technique have a better correlation with the experimental data when compared to those obtained via linear regression. Conclusively, this study has shown that CCAC can successfully be used for the removal of phenol from aqueous solutions. It also demonstrated that the modeling approach significantly affects the outcome of the analysis of dynamic adsorption systems.

Fixed Bed Adsorption/Desorption of Valeric Acid from Aqueous Solution Using Granular Activated Charcoal

n this research, the capability of Granular Activated Charcoal (GAC) for adsorbing Valeric acid (VA) from an aqueous solution was investigated in a fixed-bed column. The effect of important parameters, such as flow rate, initial concentration, bed depth, and the temperature was considered. The maximum adsorption capacity was achieved equal to 750.93 (mg/g). Length of Mass Transfer Zone (MTZ), Length of Unused Bed (LUB), and Carbon Usage Rate (CUR) were calculated. Three dynamic models (Thomas, B-A, and Yoon-Nelson) were applied in different situations. The Yoon–Nelson and Thomas models were found suitable for predicting the initial part of breakthrough curves. The FTIR tests indicated that the adsorption of VA on GAC has mainly occurred physically. The feasibility of desorbing VA from saturated GAC was also determined. The column was regenerated by using deionized water in three cycles. The desorption percentage of Valeric acid in the second and third cycles were 73% and 35%, respectively.

CO2 sorption from a mixture of N2/CO2 using an activated carbon and silica gel: equilibrium, breakthrough and mass transfer zone

<p>The temperature, feed rate, length of mass transfer zone, utilization factor and partial pressure are the parameters considered for fixed bed sorption of CO2 from N2/CO2 mixture. The breakthrough time relies strongly on the temperature and feed rate. The prolonged breakthrough and saturation times have been realized for AC. The response curves of AC are vastly steep signifying the maximal utilization of bed capacity at the breakpoint. In general, the length of MTZ increases with raised temperature and feed flow rate. The capacity utilization factor reduces with raised temperature and feed flow rate. A utilization factor of 0.919 was determined for AC. The maximal capacity for CO2 reduces significantly with an increased temperature. The maximal capacities of 32.99 gm CO2/Kg was determined at a temperature of 298 K for AC. The capacity improves considerably with CO2 partial pressure and AC exhibited higher adsorption capacity compared to SG. The capacity improves considerably with increased feed rates and maximal capacity of 39.14 g CO2/Kg adsorbent was determined for AC at the feed rate of 8.33 x10-3 m3/sec. Owing to higher sorption capacity and utilization factor, the AC may be used for economical separation of CO2 from N2/CO2 mixture</p>

Dual packed bed adsorption of sulphur dioxide from surface modified haematite / III-ferric oxide: characterization of the mass transfer zone

The adsorption process was adopted to separate SO2 from surface modified haematite / III-ferric oxide with highly positive nano-particles. Ferric oxide was produced by precipitation at a different temperature rate. Adsorption of SO2 was performed in a dual packed bed column with different process parameters such as temperature, adsorbate rate to achieve balance of isotherm. Characteristics of adsorption have been studied such as concentration gradient, exhaustion time T0.95, mass transfer zone length (LMTZ), breakthrough time T0.05 and constant rate. Chemisorption between the surfaces of ferric oxide activated and the targeted adsorbate SO2 were strongly influenced between 45 and 50 °C. The adsorbent was analysed before and after the adsorption process using the X-Ray Diffraction Method (XRD), Atomic Adsorption Spectroscopy (AAS) to investigate adsorption properties such as porosity, specific surface area (152 m2g−1), adsorption capacity and characterization. The study showed that the activated ferric oxide surface affects the adsorption process capacity more than other metal oxide surfaces. Higher specific surface area (558 m2g−1) of ferric oxide activated adsorbed more SO2 than non-activated ferric oxide at room temperature.

Dynamic Adsorption of Sulfamethoxazole from Aqueous Solution by Lignite Activated Coke.

In this paper, lignite activated coke was used as adsorbent for dynamic column adsorption experiments to remove sulfamethoxazole from aqueous solution. The effects of column height, flow rate, initial concentration, pH and humic acids concentration on the dynamic adsorption penetration curve and mass transfer zone length were investigated. Results showed penetration time would be prolonged significantly by increasing column height, while inhibited by the increasement of initial concentration and flow rate. Thomas and Yoon-Nelson model and the Adams-Bohart model were used to elucidate the adsorption mechanism, high coefficients of R2 > 0.95 were obtained in Thomas model for most of the adsorption entries, which revealed that the adsorption rate could probably be dominated by mass transfer at the interface. The average change rates of mass transfer zone length to the changes of each parameters, such as initial concentration, the column height, the flow rate and pH, were 0.0003, 0.6474, 0.0076, 0.0073 and 0.0191 respectively, revealed that column height may play a vital role in dynamic column adsorption efficiency. These findings suggested that lignite activated coke can effectively remove sulfamethoxazole contaminants from wastewater in practice.

Synthesis and characterization of high-performance activated carbon from walnut shell biomass for CO2 capture.

An increasing level of carbon dioxide (CO2) in the atmosphere has ultimately resulted in global warming and climate change. The high-performance activated carbon (AC-WL) was synthesized from walnut shell, a low-cost biomass by-product, by physical activation using a tube furnace. The adsorption behavior of CO2 from the CO2/N2 mixture was investigated using a fixed bed. The surface and morphological characterizations of the produced activated carbons were measured using a BET analyzer and a scanning electron microscope (SEM). The effect of temperature, flow rate, CO2 level, and partial pressure on breakthrough behavior was analyzed, and the adsorption response presented in terms of breakthrough point and adsorption capacity. The breakthrough and saturation periods vary significantly with change in temperature. The steepness of the breakthrough curves signifies good utilization of adsorbent capacity at breakthrough point. The increase in temperatures and flow rates lead to an increase in the length of mass transfer zone. The adsorption capacity of 1.58mmol/g was obtained at 1.30bars and 293K with higher capacity utilization factor of 0.8492.These results suggest that the walnut-based activated carbon is favorable for capturing CO2.

Intensification of Ni(II) adsorption in a fixed bed column through subcritical conditions

Adsorption for environmental applications is normally studied in gas and liquid phases. For the first time in the literature, Ni(II) was adsorbed from a subcritical water stream in a fixed column using activated carbon as an adsorbent. Several breakthrough curves were constructed at different conditions of pressure (from 5 to 25 MPa) and temperature (from 100 to 200 °C), so that, the effects of these variables on the adsorption operation were evaluated using an experimental design. The results were also compared with an adsorption in normal conditions. The fixed bed performance was largely improved when subcritical conditions were used, mainly at 25 MPa and 200 °C. The values of stoichiometric adsorption capacity (Qeq), breakthrough time (tr) and length of mass transfer zone (MTZ) were, respectively, 1.54 mg g–1, 5 min and 28.31 cm for the operation in normal conditions. Under subcritical conditions, Qeq was 6.30 mg g–1, tr was 166 min and the MTZ decreased around 10 cm. These results show that a fixed bed column containing activated carbon has better performance when adsorption take place using subcritical water instead of water under ambient conditions.

Powdered biosorbent from the mandacaru cactus (cereus jamacaru) for discontinuous and continuous removal of Basic Fuchsin from aqueous solutions

A powdered biosorbent was developed by the processing of mandacaru (Cereus jamacaru) leaves, and tested as an alternative material to treat solutions containing Basic Fuchsin dye (BF) in discontinuous and continuous systems. A simple model (ILE model) based in the Langmuir isotherm was developed to predict the continuous biosorption. PML was a fast and efficient biosorbent, attaining biosorption capacity near to 400 mg g−1. PML was also efficient to treat a simulated effluent, providing color removal percentages around 90%. In relation to the continuous operation using PML, an excellent bed performance was found, with breakthrough time of 14 h, and length of mass transfer zone of 1.48 cm. The ILE model was able to predict the breakthrough curve. It can be concluded that PML is a low cost and efficient biosorbent to be used for decolorization of liquid streams in discontinuous and continuous systems.

Comparison of structured activated carbon and traditional adsorbents for purification of H2

RPSA technology can offer a more compact, cost-effective and energy-efficient solution for H2 recovery when compared to conventional PSA. The adsorption rate of adsorbents has become a key factor affecting the development of RPSA. Activated carbon, widely used as adsorbent for CO2 in H2 purification is in urgent need for further development to suitable for RPSA system. In this study, a structured activated carbon adsorbent was prepared using the dip-coating method, with nickel foam as a framework. The adsorption characteristics of the material for CO2 adsorption at different adsorption pressures, volume flow rates, and lamellar spacing parameters were investigated, and the kinetic behaviour was studied by the breakthrough curve. The results showed that the activated carbon was bonded to the nickel foam skeleton via an organic-inorganic binder with excellent mechanical strength. Structured adsorbents bed has uniform gas flow distribution, the pressure drop is about 1/3–1/7 of particles packed bed, and the breakthrough curve was sharper than particles. It indicated that the mass-transfer resistance in the structured adsorbents is low and has high effective diffusivity for CO2. The adsorption rate constant was calculated using the Yoon-Nelson model, and the correlation between the model calculation data and experimental data was greater than 0.98. Structured activated carbon adsorbent manufactured by dip-coating method, has a higher mass transfer coefficient and a shorter mass transfer zone length. It is a potential alternative adsorbent for RPSA.

Adsorptive decontamination of wastewater containing methylene blue dye using golden trumpet tree bark (Handroanthus albus).

The golden trumpet tree bark (GTB), a wood-processing residue, was tested as adsorbent material for decontamination of wastewaters containing methylene blue dye (MB). The powdered material was preponderantly amorphous, containing an irregular surface with the presence of lignin and holocellulose. The adsorption was favorable at basic pH of 10 and adsorbent dosage of 0.5gL-1. The kinetics has finished in only 30min and fitted by the general order model (GO). The isotherm behaviors were successfully represented by the Langmuir model. The value found for the maximum adsorption capacity was 232.25mgg-1, being obtained at 328K. The standard variation of Gibbs free energy (ΔG0) ranged from - 10.77 to - 8.09kJmol-1, indicating a spontaneous and favorable adsorption. A variation of standard enthalpy (ΔH0) of 18.58kJmol-1 revealed an endothermic adsorption. A sloped forward curve was found in the continuous operation, with breakthrough time (tb) of 325min. The stoichiometry capacity of the column (qeq) and the length of mass transfer zone (Zm) were, respectively, 23.57mgg-1 and 11.28cm. The GTB was efficient in the treatment of a simulated effluent, obtaining color removal of 96%. These results show that GTB can be applied as adsorbent for decontamination of wastewaters containing methylene blue.

H2S adsorption on NaY zeolite

Abstract In this work, high-pressure H2S adsorption data in equilibrium and fixed bed conditions using NaY zeolite as adsorbent were determined. Adsorption and desorption isotherms for different temperatures and H2S partial pressures up to 1.2 bar were obtained experimentally and modelled with Toth and Dubinin-Astakhov equations in order to give information about adsorbate/adsorbent and adsorbate/adsorbate interactions. H2S adsorption in a fixed bed column was achieved for different inlet volumetric flow rates and breakthrough curve data were evaluated considering adsorbed amount, length of mass transfer zone, contributions of internal and external mass transfer resistances and were modelled with Linear Driving Force (LDF) model to estimate adsorbent particle's effective mass transfer coefficient. Equilibrium results indicate maximum uptake capacities are above 6.0 mol kg−1 for highest partial pressures. Isotherms' modeling suggests the predominance of physisorption of H2S in NaY zeolite. However, a hysteresis effect was observed for desorption curves and attributed to H2S chemisorption on zeolite surface, as pointed out by strongly favorable isotherms obtained. Fixed bed adsorption data showed breakthrough curves were nonsymmetrical, which indicated the presence of internal resistance mainly, probably due to the microporosity of adsorbent particle. In accordance, mass transfer zones did not vary significantly with inlet flow rate. Effective intraparticle mass transfer coefficients obtained with LDF model increases as flow rate increases, due to a higher availability of H2S molecules at adsorbent surface, which increases the driven force necessary for mass transfer in the intraparticle region.