Adsorption Breakthrough Research Articles

Adsorption Evaluation with Zeolites for Gases in the Confined Space

The high humidity characteristics of the confined space challenge the zeolites with good water performance. In this study, the adsorption of N2, CO2, H2, CH4, CO and H2O vapor by zeolites (5A and 13X) were discussed, and the structure of zeolites were characterized by XRD, FTIR and SEM. The adsorption breakthrough curve of CO2 was measured by the fixed bed reactor, and the adsorption characteristics were obtained under different temperatures and gas velocities. The results showed that 13X-2 zeolite had the CO2 adsorption capacity of 100.1 cm3·g−1, which is higher than the others, and the appropriate water stability.

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.

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.

Removal of siloxane (L2) from biogas using methyl-functionalised silica gel as adsorbent

Volatile methylsiloxanes (VOSiC) are impurities present in trace amounts in biogas produced by the anaerobic digestion of organic wastes in landfill and sewage plants. Efficient removal of these impurities is required due to the restrictions posed by them on the application of biogas as an alternative energy resource. In this study, methyl-functionalised silica gels (MFS) have been prepared via a hydrolysis and condensation approach using double precursor (TEOS and MTS) in methanol–water medium for achieving effective removal of a model VOSiC - hexamethyldisiloxane (L2). The developed gels have been characterized by N2-BET, FTIR, SEM-EDS and XRD. The results reveal that the as-synthesized MFS materials have well-developed micropore structure and superhydrophobicity. Among the developed materials, MFS2 sample obtained with a MTS/TEOS ratio of 1/1 (v/v) exhibits the highest specific surface area (1261.3 m2 g−1), micropore volume (0.52 cm3 g−1) and total pore volume (1.03 cm3 g−1), along with superior water contact angle (123.5°). The non-crystalline nature and sponge-like structure of MFS are confirmed by XRD and SEM analyses. The adsorptive performance of MFS materials for L2 siloxane is measured to be 14.9–18.3 times higher than that of the unmodified silica in terms of the breakthrough adsorption capacity (QB). Also, the adsorption capacities of MFS materials are noted to be linearly related to the specific surface area and micropore volume, along with positively affected by the total pore volume and water contact angle. From a series of the experimental results of adsorption of L2 by MFS2, an empirical equation is developed for reflecting the correlation of the breakthrough time and inlet concentration. Use of lower temperature is concluded to result in better overall siloxane adsorption levels. The QB reaches an optimal value of 346.3 mgL2 g−1 at 0 °C using 83.82 mg L−1 of L2 with N2 as the carrier gas. The developed MFS adsorbent can be readily regenerated for reuse by heating at 80 °C, and an insignificant fluctuation in the dynamic adsorption behavior is observed even after consecutive 5 adsorption/desorption cycles.

Cyclic performance evaluation of a polyethylenimine/silica adsorbent with steam regeneration using simulated NGCC flue gas and actual flue gas of a gas-fired boiler in a bubbling fluidized bed reactor

To accelerate the deployment of Carbon Capture and Storage (CCS) based on the solid amine adsorbents towards a practical scale application relevant to Natural Gas Combined Cycle (NGCC) power plants, this study has evaluated the cyclic performance of a polyethylenimine/silica adsorbent of kg scale in a laboratory scale bubbling fluidized bed reactor. A high volumetric concentration 80−90 vol% of steam mixed with N2 and CO2 has been used as the stripping gas during a typical temperature swing adsorption (TSA) cycle. Both the simulated NGCC flue gas and the actual flue gas from a domestic gas boiler have been used as the feed gas of the CO2 capture tests with the solid adsorbent. Various characterization has been carried out to elucidate the possible reasons for the initial capacity decline under the steam regeneration conditions. The effect of presence of CO2 in the stripping gas has also been studied by comparing the working capacities using different regeneration strategies. It has been demonstrated that the breakthrough and equilibrium CO2 adsorption capacities can be stabilized at approximately 5.9 wt% and 8.6 wt%, respectively, using steam regeneration for both the simulated and actual natural gas boiler flue gases. However, using a concentration of 15 vol% CO2 in the stripping gas has resulted in a significantly low working capacity at a level of 1.5 wt%, most likely due to the incomplete CO2 desorption and degradation in a CO2 containing environment.

Carbon nanoflake hybrid for biohydrogen CO 2 capture: Breakthrough adsorption test

Carbon nanoflake hybrid for biohydrogen CO ₂ capture: Breakthrough adsorption test

Accelerated C2H2/CO2 Separation by a Se-Functionalized Porous Coordination Polymer with Low Binding Energy.

High-quality pure acetylene (C2H2) is a kind of crucial starting material for various value-added products. However, selective capture of C2H2 from the main impurity of CO2 via porous absorbents is a great challenge, as they possess extremely similar kinetic diameters and boiling points, as well as the explosive and reactive properties of C2H2. Herein, we report a porous coordination polymer (PCP), (NTU-55), which assembled from the coordination between a Cu dimer and a newly designed ligand with a nonmetal selenium (Se) site. Static single-component adsorption and dynamic breakthrough experiments reveal that desolvated NTU-55 can completely adsorb C2H2 from the C2H2/CO2 mixture (1/4, v/v) at 298 K, along with higher C2H2 capacity and much lower binding energy. The origin of this separation, as comprehensively revealed by density functional theory (DFT) calculations, is derived from the interaction discriminatory of C2H2 and CO2 toward accessible Se and Cu adsorption sites. To the best of our knowledge, this is the first time to find the positive effect of nonmetal Se sites for selective C2H2 capture.

Hydrophobic interaction chromatography as polishing step enables obtaining ultra-pure recombinant antibodies

Hydrophobic interaction chromatography is a versatile method to polish antibodies. Here, we present a polishing procedure in order to obtain an ultra-pure preparation of antitumor necrosis factor (TNF) alpha IgG1. Hydrophobic interaction chromatography (HIC) was used with Toyopearl® Phenyl 650M adsorbent in the presence of ammonium sulfate. Adsorption isotherms, breakthrough curves and chromatographic runs were carried out. The eluted antibody was recovered with 99.9 % purity and 96.2 % yield. In the main peak, aggregates, host cell proteins (HCP) and DNA content were below the limit of detection of the analytical methods used. Thus, the method proposed here shows potential to be employed in a downstream process when an ultra-pure antibody preparation is required.

Fabrication of effective desulfurization species active sites in the CeY zeolites and the adsorption desulfurization mechanisms

A series of CeY zeolites with different cerium loadings and calcined at different temperatures were prepared and used as the adsorbent for the desulfurization of thiophene containing model oil. The CeY zeolites were characterized by XRD, N2 sorption, FT-IR spectroscopy and GC-SCD and GC-MSD techniques. The effects of aromatics and olefins on the adsorption desulfurization performance were investigated and the active species and reaction mechanism for the adsorption desulfurization on CeY zeolites were probed. The results indicate that the CeY zeolite calcined at 150°C is provided with a large number of Brönsted acid sites and hydroxylated cerium species in the supercages, which can synergistically promote the thiophene oligomerization and then enhance the sulfur breakthrough adsorption capacity (18.45 mg(S)/g). However, a further increase in the calcination temperature and cerium loading may greatly reduce the number of active sites for the adsorption desulfurization and suppress the thiophene oligomerization reaction, leading to a significant decrease in the sulfur breakthrough adsorption capacity (4.03 mg(S)/g). For the thiophene model oils containing low concentration of 1-hexene (< 1.0%) or benzene (< 0.1%), the CeY-12.3-150 zeolite (with a cerium loading of 12.3% and calcined at 150°C) also exhibits a relatively high sulfur breakthrough adsorption capacity. However, a further increase in the content of 1-hexene or benzene in the feed may lead to a sharp decrease in the sulfur breakthrough adsorption capacity, due to the alkylation of thiophene and the adsorption mode of “S–H” bonding.

Carbon nanotube sponges as an enrichment material for aromatic volatile organic compounds

Sensitive methods are required for in situ monitoring of volatile organic compounds (VOCs). Herein, carbon nanotube (CNT) sponges were investigated as a new type of adsorbent for enriching trace aromatic VOCs. A square pillar configuration (3 mm × 3 mm × 45 mm, 5 mg) of a CNT sponge was enclosed in a glass tube (4 mm i.d.). After accumulating the sample vapor, a direct current pulse (26 V, 0.5–3.0 s) through the CNT sponge allowed narrow desorption bandwidths of 0.48−0.84 s (with a photoionization detector) and 1.2 s (with a flame ionization detector) and high desorption efficiency (>96.5%). Gas chromatographic analysis of a nine-component VOC mixture (100 mL adsorption volume) gave enrichment factors of 88 (benzene) to 323 (toluene and m-xylene) with detection limits in the range of 0.9−2.6 ppb (v/v). These results demonstrate that CNT sponges are a promising preconcentrator material for trace detection of VOCs. The adsorption breakthrough experiments exhibited good correlation with the kinetic adsorption and Langmuir isotherm models. The maximum adsorption capacities of the CNT sponge increased in the order benzene (0.13 mg/g) < toluene (2.45 mg/g) < ethylbenzene (13.90 mg/g) < o-xylene (14.31 mg/g), with R2 values of >0.95. The rollup phenomena observed during multicomponent adsorption were explained by the competitive displacement or adsorption affinities of aromatic VOCs. The feasibility of the CNT sponge preconcentrator in a real environment was tested for interfering species (NO2 and NH3), laboratory air, and a human breath sample and demonstrated similar performance as in the controlled nine-component tests.

Simultaneous capture of NH3 and H2S using TiO2 and ZnO nanoparticles - laboratory evaluation and application in a livestock facility

Simultaneous removal of ammonia (NH3) and hydrogen sulphide (H2S) from pre-mixed gases and stored swine manure gases were investigated in laboratory and semi-pilot scale systems and in a swine production facility, using TiO2 and ZnO nanoparticles. Increase of NH3 concentration in the mixture from 50 to 500 ppmv led to higher breakthrough and equilibrium adsorption capacities, while increase of temperature had an opposite effect. Equilibrium adsorption capacities at 22 °C were in the range 6.92–11.95 mg NH3 g−1 and 1.35–3.57 mg NH3 g−1 at 280 °C. Increase of H2S concentration up to a certain level led to higher equilibrium adsorption capacities but no dependency between breakthrough adsorption capacity and H2S concentration was observed. Both breakthrough and equilibrium adsorption capacities increased with the increase of temperature. The highest equilibrium adsorption capacity of 52.31 mg H2S g−1 was obtained with 550 ppmv H2S in the mixture at 140 °C, while the lowest value was 14.55 mg H2S g−1 with 50 ppmv H2S at 22 °C. At low temperature (22 °C) NH3 adsorption occurred through both physical adsorption and chemisorption, while at 280 °C chemisorption was the dominant mechanism. A sulfidation reaction involving ZnO and H2S that was favored by higher temperatures was evident. Treating gases emitted from stored swine manure in a semi-pilot scale adsorption system led to complete elimination of NH3 and H2S. Application of a nano-based air filtration-circulation system with ZnO and TiO2 nanoparticles in a swine production room during manure handling led to removal efficiencies of 67–100% for H2S and 50–100% for NH3.

Adsorption of perfluoroalkyl substances (PFAS) in groundwater by granular activated carbons: Roles of hydrophobicity of PFAS and carbon characteristics

The adsorption breakthrough behavior of nine perfluoroalkyl substances (PFAS) in groundwaters by four bituminous coal-based granular activated carbons (F400, Carbsorb 40, HPC and CMR400) was studied using rapid small-scale column tests (RSSCTs). The half breakthrough bed volume (BV50), an indicator of apparent adsorption capacity, correlated with the hydrophobicity of PFAS at a given pH (i.e., Log Dow) for F400, indicating that hydrophobic interaction is important for apparent adsorption capacity of PFAS in groundwater with low dissolved organic concentrations (DOC < 1 mg C/L) and low specific UV absorbances at 254 nm (SUVA254 < 2 L mg−1m−1). Higher empty bed contact time (EBCT) caused steeper PFAS breakthrough curves with respect to throughput, but did not affect apparent adsorption capacity. Three different sizes of F400 (0.13, 0.17, and 0.20 mm) exhibited similar breakthrough profiles of PFAS, indicating that the intraparticle diffusivity was independent of adsorbent diameter in the given conditions. Among the tested carbons, the positively charged adsorbents (F400, HPC, and CMR400) showed higher apparent adsorption capacities for hydrophilic (Log Dow at pH 7 < 0) and marginally hydrophobic PFAS (Log Dow at pH 7 between 0 and 1) than the negatively charged adsorbent (Carbsorb 40). In addition, activated carbons with higher micropore surface areas exhibited higher apparent adsorption capacities of hydrophilic and marginally hydrophobic PFAS among the positively-charged activated carbons, whereas the mesoporous carbon (HPC) exhibited an increasingly larger adsorption capacity for more hydrophobic PFAS compared to the microporous carbon (F400) at a later breakthrough possibly due to less pore blockage.

Total organic acid adsorption using alginate/clay hybrid composite for industrial lean amine reclamation using fixed-bed: Parametric study coupled with foaming

The technical feasibility of removing heat stable salts (HSS) such as total organic acids (TOA) from industrial lean methyldiethanolamine (MDEA) solutions using calcium alginate/clay hybrid (CAH) composite adsorbent in a continuous fixed bed adsorber has been investigated. The effect of process parameters such as bed diameter, bed height, feed flow rate, and flow direction on breakthrough time, adsorption capacity, and exhaustion time of the fixed-bed sorption system was analyzed. Experimental results showed that higher bed diameter and height, lower flow rate along with up-flow column mode resulted in increased uptake capacity and breakthrough time. Progressive reduction in adsorption capacity from 3.6 mg/g to 2.83 mg/g after three adsorption/desorption cycles using 4.0 wt. % CaCl2 confirmed the practicability of the adsorbent. Simulation of breakthrough curves using general reaction rate models such as Bohart-Adams and Yoon-Nelson yielded a high correlation coefficient (R2 > 0.93), and thus validating the applicability of these models to predict the break through curves under various operating conditions. Furthermore, foaming experiments confirmed the vital role of CAH composite in reducing the foamability of lean MDEA solutions through the synergistic effect of successive biosorption and robustness of the saturated composites to multiple in-situ regeneration using CaCl2.

Adsorption of anionic and cationic dyes into shaped MCM-41

The adsorption of Basic Blue 41 (BB41), Methylene Blue (MB) and Basic Red 18 (BR18), three known basic dyes, was studied in shaped mesoporous adsorbent MCM-41. The granules were obtained by extrusion of the powder adsorbent and were analyzed by nitrogen adsorption, SEM–EDS, XRD, mercury porosimetry and helium picnometry. Adsorption equilibrium isotherms, kinetics, and breakthrough curves were performed with the selected adsorbent and dyes. The experimental results indicated that the Sips model better describes the equilibrium than the Langmuir and Freundlich isotherm models. Additionally, the co-adsorption equilibrium of two dyes was well predicted by the extended form of the Sips model. The kinetics results showed that the adsorption of Basic Blue 41 onto the selected adsorbent is faster than with the other studied dyes. The obtained adsorbed equilibrium amounts through the breakthrough curves were 308 mg g−1, 55 mg g−1 and 106 mg g−1 for the Basic Blue 41, Methylene Blue and Basic Red 18 dyes, respectively. The dye is concentrated during regeneration step, since the volume of regenerating solution, eluted during the regeneration, is considerably lower (about two orders of magnitude) when compared with the volume of effluent treated until the breakthrough point. This fact demonstrates the feasibility of a potential adsorption based process to treat dyed effluents, with the shaped MCM-41.

New insights from modelling and estimation of mass transfer parameters in fixed-bed adsorption of Bisphenol A onto carbon materials

The removal of Bisphenol A, 2,2-bis (4-hydroxyphenyl) propane (BPA) in fixed-bed columns was investigated by breakthrough adsorption tests at different operation conditions and further prediction by a mathematical model to describe the adsorption-diffusion process onto two synthesized carbon porous materials. In this study, a xerogel (RFX) prepared by an optimized conventional sol-gel method and a lignin-based activated carbon (KLP) obtained via chemical activation were used in batch and fixed-bed adsorption experiments. The materials were fully characterized and their adsorptive properties were compared to those obtained with a commercial activated carbon (F400). RFX and KLP materials reached the equilibrium adsorption in only 24 h, whereas F400 activated carbon required 48 h. In addition, F400 and KLP adsorbents showed higher equilibrium adsorption capacity values (qe = 0.40 and 0.22 kg/kg, for F400 and KLP, respectively) than that obtained for the xerogel (qe = 0.08 kg/kg). Both synthesized carbon-adsorbents were studied in fixed-bed adsorption tests, exploring the effect of the operation conditions, e.g., initial BPA concentration (0.005–0.04 kg/m3), weight of adsorbent (0.01–0.05 g) and volumetric flow rate (0.2 to 1.0 mL/min), on the adsorption performance of the column. All the tested adsorption columns reached the equilibrium in a very short time, due to the efficient dimensionless of the bed. Additionally, the regeneration of the exhausted adsorbent was studied, achieving the total reuse of the solids after three consecutive cycles using methanol as regeneration agent. Finally, a mathematical model based on mass conservation equations was proposed, allowing to efficiently fit the experimental BPA breakthrough curves and estimate the external and adsorbed-phase mass transfer coefficients with a high accuracy.

Thermodynamic Separation of 1-Butene from 2-Butene in Metal-Organic Frameworks with Open Metal Sites.

Most C4 hydrocarbons are obtained as byproducts of ethylene production or oil refining, and complex and energy-intensive separation schemes are required for their isolation. Substantial industrial and academic effort has been expended to develop more cost-effective adsorbent- or membrane-based approaches to purify commodity chemicals such as 1,3-butadiene, isobutene, and 1-butene, but the very similar physical properties of these C4 hydrocarbons make this a challenging task. Here, we examine the adsorption behavior of 1-butene, cis-2-butene, and trans-2-butene in the metal-organic frameworks M2(dobdc) (M = Mn, Fe, Co, Ni; dobdc4- = 2,5-dioxidobenzene-1,4-dicarboxylate) and M2(m-dobdc) (m-dobdc4- = 4,6-dioxidobenzene-1,3-dicarboxylate), which all contain a high density of coordinatively unsaturated M2+ sites. We find that both Co2(m-dobdc) and Ni2(m-dobdc) are able to separate 1-butene from the 2-butene isomers, a critical industrial process that relies largely on energetically demanding cryogenic distillation. The origin of 1-butene selectivity is traced to the high charge density retained by the M2+ metal centers exposed within the M2(m-dobdc) structures, which results in a reversal of the cis-2-butene selectivity typically observed at framework open metal sites. Selectivity for 1-butene adsorption under multicomponent conditions is demonstrated for Ni2(m-dobdc) in both the gaseous and the liquid phases via breakthrough and batch adsorption experiments.

Highly Structured Nanofiber Zeolite Materials for Biogas Upgrading

Hierarchical zeolite composite nanofibers are designed using an electrospinning technique with post‐carbonization processing to form mechanically strong pellets for biogas upgrading. A ZSM‐5 nanopowder (zeolite) and a polyvinylpyrrolidone (PVP) polymer are electrospun to form ZSM/PVP composite nanofibers, which are transformed into a ZSM and carbon composite nanofiber (ZSM/C) by a two‐step heat treatment. The ZSM/C nanofibers show a 30.4% increase in Brunauer–Emmett–Teller (BET) surface area compared with the non‐structured ZSM‐5 nanopowder. Using ideal adsorbed solution theory, CO2‐over‐CH4 selectivity of 20 and CO2 uptake of 2.15 mmolg−1 at 293 K at 1 bar for ZSM/C nanofibers are obtained. For the efficient use of adsorbents in pressure swing adsorption operation, the nanofibers are structured into ZSM/C pellets that offer a maximum tensile strength of 6.46 MPa to withstand pressure swings. In the breakthrough tests, the CO2 uptake of the pellets reach 3.18 mmolg−1 at 293 K at 4 bar after 5 breakthrough adsorption–desorption cycles, with a much higher mass transfer coefficient of 1.24 ms−1 and CO2 uptake rate of 2.4 mg of CO2 g−1s−1, as compared with other structured zeolite adsorbents.

High efficiency of toluene adsorption over a novel ZIF-67 membrane coating on paper-like stainless steel fibers

A novel microporous ZIF-67 membrane coating on paper-like stainless steel fibers (ZIF-67 membrane/PSSF) was successfully synthesized by a wet layup papermaking-sintering method followed by the seed-induced growth method. The effects of key factors such as crystallization temperature, synthesis time and Hmim/Co2+ (2-methylimidazole/cobalt chloride) molar ratio on the morphology structure of the samples were studied by the modern characterization techniques including SEM, EDX, TEM, XRD, BET, FTIR and TGA, respectively. The experimental result indicated that the as-synthesized ZIF-67 membrane/PSSF was extremely compact with the average membrane thickness of 4.8 μm. And the sample exhibited high BET surface area (440.9 m2/g), uniform pore size (1.881 nm) and large pore volume (0.2096 cm3/g). The adsorption breakthrough experiment of toluene was performed on different bed reactors filled with ZIF-67 membrane/PSSF and granular ZSM-5 zeolites, respectively. The experiment data was well fitted by Yoon–Nelson model, where the values of rate constant in the fixed bed with ZIF-67 membrane/PSSF increased by 32.2% compared with that of commercial ZSM-5 zeolites at the flow rate of 100 mL/min. And the bed pressure drop and length of unused bed (LUB) were dramatically reduced by 39.6% and 16.8% in 3 cm ZIF-67 membrane/PSSF fixed bed. In conclusion, mass transfer efficiency was significantly enhanced based the structured ZIF-67 membrane/PSSF fixed bed, and this new material is a promising adsorptive material for VOCs removal.

Removal of styrene by the synthesized ZnO nanoparticles coated on the activated carbon adsorbent in the presence of UV irradiation

Background: Volatile organic compounds are the major environmental pollutants causing adverse effects on the human health and the environment, therefore, tremendous effort has been put toward eliminating these compounds. Methods: In this study, the effect of synthesized nanoparticles on the removal of styrene from gas phase by photocatalytic process under UV irradiation in the cylindrical photoreactor was studied. The activated carbon-zinc oxide (AC-ZnO) catalysts were prepared at different weight ratios (6%, 12%, and 18%) of ZnO. The prepared catalyst was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Brunauer-Emmett-Teller (BET) analyses. The effects of various parameters, such as concentrations of styrene, various weight percentage (wt%) of nanoparticles, and UV irradiation, were investigated. The efficiency of the AC-ZnO catalyst was determined based on its adsorption capacity, breakthrough time, and removal efficiency. Results: It was revealed that the photocatalytic removal efficiency of styrene was high in the presence of both ZnO nanoparticle and AC under UV light. Under optimal conditions, the efficiency of UV/ACZnO 18%, UV/AC-ZnO 12%, and UV/AC-ZnO 6% catalysts was 77%, 86%, and 83%, respectively. By increasing the concentration of input styrene, the photocatalytic removal efficiency was reduced, while the adsorption capacity of styrene increased. Conclusion: According to the results, the AC-ZnO 12% exhibited higher activity compared to other photocatalysts. Also, the amount of stabilized ZnO nanoparticles on the activated carbon affects the elimination rate of styrene.

Removal of silica from brackish water by integrated adsorption/ultrafiltration process.

A lab-scale unit of the hybrid continuous stirred tank reactor (CSTR) adsorption/ultrafiltration (UF) system was used to evaluate the removal efficiency of silica from brackish water. The semi-batch adsorption process was carried out using iron oxy/hydroxide agglomerates (IOAs) as adsorbent and hollow fiber ultrafiltration membrane as a barrier to the adsorbent passage to the product water. The effect of residence time, concentration of silica, and adsorbent dosage on the silica removal and UF membrane blockage was examined. It was found that a short residence time of 15min was sufficient to achieve the maximum adsorption capacity similar to that obtained in batch isotherm experiments. The adsorption capacity increased with the augmentation of the silica concentration and decreased with the increase in the adsorbent dosage. The UF was effectively employed to separate the loaded adsorbent without fouling the membrane until breakthrough. A simple model was applied to accurately predict the adsorption breakthrough curves.