Total Adsorption Research Articles

A high-and-rapid-response capacitive humidity sensor of nanoporous anodic alumina by one-step anodizing commercial 1050 aluminum alloy and its enhancement mechanism

Anodic aluminum oxide (AAO) is a well-known nanoporous material and a template for nanotechnology application. The AAO based humidity sensor is traditionally fabricated using low-temperature (0–10 °C) two-step anodization in oxalic acid at 40 V from the expensive high-purity aluminum of small-area as well with low response and low intensity. Here, one-step anodizing commercial large-area low-purity aluminum 1050 alloy was realized for high-performance humidity sensor by hybrid-pulse anodization in 0.3 M oxalic acid at 20 V at 25 °C that merits low cost, short fabrication time and high-and-rapid capacitive response. The performance enhancement is attributed to the increased total pore area adsorption ratio and the electrode area of AAO with lower thickness to make much more water vapor molecules adsorb onto the wall surface of pores for sensing with high capacitance, response and short response-recovery time. The low-thickness pores make water molecules adsorb onto and desorb from the pores surface more quickly because of shorter diffusion path. Also, a small-area sample of traditional 40 V AAO is used as a reference for comparison. A shorter anodization time of 55 min is also fabricated for understanding the thickness effect on the response-recovery time. The large-area AAO humidity sensor of 16 cm2 at 20 V exhibits high response (above 5000 %, 3.5 times the traditional reference) and quick response-recovery time (9 s). The high-and-rapid-response enhancement mechanism of AAO capacitive humidity sensor is established.

Electrostatic properties of C–S–H and C-A-S-H for predicting calcium and chloride adsorption

The adsorption capacity of cement hydrates considerably affects the ionic ingress into cementitious materials. In this study, the surface electrostatic properties of calcium silicate hydrate (C–S–H) and calcium aluminosilicate hydrate (C-A-S-H) were determined to understand the effects of the properties on calcium and chloride adsorption. The density of the surface functional groups was determined by analysing the structure of C–S–H and C-A-S-H through 27Al and 29Si MAS NMR. The surface sites of ≡SiOH and ≡AlOH are available in C-A-S-H whereas C–S–H has ≡SiOH groups for ionic adsorption. We found that the incorporation of aluminium decreases the number of total adsorption sites in C-A-S-H. Furthermore, the site density increased with Ca/(Si + Al). To understand the C-A-S-H/solution interface, a triple-layer surface complexation model was developed and the associated equilibrium constants for deprotonation, calcium, and chloride adsorption were determined by fitting the experimental data of potentiometric titration and zeta potential measurement results. The estimated surface complexation modelling parameters were verified by predicting the experimental data of calcium and chloride adsorption on C–S–H and C-A-S-H.

Генетико-географические закономерности структурно-минералогической величины поглотительной способности сероземных почв Нахичевани

The correlation of indicators of the mineralogical and chemical composition, greatness and structure of the general serozem soils adsorption capability of the low part in Nakhchivan have been investigated. A methodology is being developed for assessing the greatness and structure of the absorption capability with different rocks. The geography of the serozem soils absorption capability is also determined by the correlation of soil-formed and inherited components in different serozem soils, which also gives grounds to use the bioclimatic factors of zonal soils. The regularities of the genesis and geography of the total adsorption capability have been revealed, which can be used for monitoring and prognosis contaminated soils with various substances, including heavy metals.

Carboxylic acid reduction and sulfate-reducing bacteria stabilization combined remediation of Cr (VI)-contaminated soil

For controlling heavy metal pollution, the utilization of carboxylic acids (CAs) combined with sulfate-reducing bacteria (SRB) for continuous and stable remediation of Cr (VI)-contaminated soil was comprehensively investigated. At pH 3, citrate and lactate had photocatalysis characteristics that enabled them to reduce high Cr (VI) concentrations. The reduction efficiencies of citrate and lactate were 99.16–100% and 80.78–87.00%, respectively. In the 40 mg L−1 Cr (VI) treatment, the total Cr adsorption rate of soil was 61.39–68.31%; as the pH increased, the Cr species adsorption capacity of the soil decreased. Following the addition of exogenous 100 mg L−1 Cr (VI), the Cr (VI) content of re-contaminated soil was reduced to 16.2734 ± 0.9505 mg L−1 or 15.8618 mg kg−1 by adding citrate or lactate. Then, using SRB via culture by mulching, addition of citrate or lactate markedly reduced the toxicity of Cr (VI). The respective citrate or lactate treatments had sulfur concentrations of sulfide from deep soil (high-sulfide layer) of 70.54 ± 17.59 and 98.85 ± 13.84 mg kg−1, respectively, and released Cr (VI) concentrations of 0.22 ± 0.25 and 3.64 ± 3.32 mg kg−1, respectively, due to oxidation upon air exposure. We used a two-stage remediation strategy for these treatments: First, CAs were used for photocatalytic reduction to reduce Cr (VI); next, CAs were utilized as carbon sources by SRB, which further reduced Cr (VI) and stabilized Cr species. In addition, citrate was more conducive than lactate to maintaining the stability of the soil microbial community. The results show that this method has potential in the remediation of Cr (VI)-contaminated soil.

A comparative adsorption kinetic modeling of fluoride adsorption by nanoparticles and its polymeric nanocomposite

Nanoparticles (NPs) of metallic oxides/hydroxides (oxyhydroxide) are highly efficient adsorbents for pollutants but tend to agglomerate readily. So, in recent years, NPs have been embedded inside the porous polymeric matrix to decontaminate pollutants more efficiently than NPs alone. But the roles of the polymeric barrier on the performance of composite adsorbent have not been explored in literature. In the present study, diffusivity coefficients (De) of fluoride ions (F-) for adsorbents mixed metal oxyhydroxides and nanocomposite were estimated using a kinetic model to understand the roles of the polymeric barrier on adsorbate diffusion from the external surface to interior pores of the nanocomposite. Adsorption kinetic modeling study of both adsorbent-F- systems reveals that Fe-Al-Mn@chitosan composite is a more efficient adsorbent than mixed metal oxide nanoparticles alone. Although, the mass fraction of metal oxides/hydroxide present in the polymeric composite is less. The kinetic model reveals that only 25% of adsorption front radius was accessible for the adsorption of fluoride ions in mixed metal oxyhydroxide (Fe-Al-Mn) NPs. But, More than 80% of the total adsorption front radius was accessible for Fe-Al-Mn@chitosan. The magnitude of De is found to be almost in the same order for both the adsorbents, proving that polymer layers in Fe-Al-Mn@chitosan composite provide minimum resistance to the internal pore diffusion of adsorbate ions from the external surface to interior pores.

Plastic shed production intensified secondary soil salinization in perennial fruit production systems

Secondary soil salinization is a common problem in intense agroecosystems such as the plastic shed production (PSP) systems. Understanding the dynamic changes of soil salinity and its negative impacts on crop nutrition is essential for management of PSP systems. In this study, 96 plastic shed orchards were chosen to investigate the impact of long-term PSP on soil salinization in a perennial fruit production county in Shaanxi Province, West China. The following results were obtained by comprehensively analyzing the profile distribution, spatiotemporal distribution, and the composition of soil salinity in PSP systems. Compared with the cereal and natural soil, PSP soil had significantly higher soil nutrients in addition to lower soil pH and greater soil electrical conductivity (EC) values. Soil EC had significant positive correlations with the total soluble salt (TSS) and sodium adsorption ratio in PSP soil profiles (p < 0.01). Thus, the high EC value (1082.2 ± 1200μScm−1) of PSP soil indicated high soil salinity content and Na+ concentration in the soil solution in the study area. The average content of TSSs in the topsoil of the soil profiles in PSP systems reached 2.23 g kg−1, indicating moderate salinization (2 g kg−1 ≤TSS<4 g kg−1). Furthermore, soil EC had a positive correlation with the PSP cropping duration and a negative correlation with the Ca concentration in fruit tree leaves in PSP systems. These findings suggest that increasing soil salinity might suppress the nutrient uptake by PSP fruit trees. Overall, this study concludes that high inputs of agrochemicals, high evaporation, and minimal leaching in PSP systems significantly intensify secondary soil salinization, as well as high Na+ accumulation in surface soil, which threaten the growth of fruit trees and soil functions.

BN Nanoflake for Hazardous SO2 Gas Capturing: DFT Study

Density functional theory (DFT) calculations were performed to investigate an idea of employing boron nitride (BN) nanoflake for hazardous SO2 gas capturing process regarding the gas pollutant problems of environmental issues. To do this, a representative model of hydrogen capped B12N12 coronene-like surface was considered for such a gas capturing process. Two starting positions were chosen for SO2 gas, once perpendicularly locating the S side of SO2 towards the BN surface to form the S@BN model and once more perpendicularly locating the O side of SO2 towards the BN surface to form the O@BN model. All singular and complex models were optimized to achieve the minimized energy structures, which were all confirmed by avoiding imaginary frequencies. Subsequently, molecular descriptors were achieved to discuss the problem of this work. The results indicated significant impacts of SO2@BN complex formation on the molecular properties, in which the levels energies of molecular orbitals were detected such impacts. Total energies and adsorption energies were meaningful for both complex formations with better O@BN model formation than S@BN one. Consequently, the investigated SO2@BN complex system could be proposed for further investigating such activities of pollutant gas sensing and removal regarding the environmental issues.

TiO2/rectorite-trapped cellulose composite nanofibrous mats for multiple heavy metal adsorption

The anthropogenic release of highly toxic heavy metals into the environment presents a huge challenge for ecosystems and human society. Recoverable and efficient adsorption materials could be obtained by trapping inorganic adsorbents (e.g., TiO2 nanoparticles and rectorite (REC)), in a natural polymer matrix. In this study, a series of cellulose-TiO2/REC composite nanofibrous mats were fabricated via electrospinning. The interactions between inorganic adsorbents and cellulose molecules improved the thermal stability, surface area, tensile strength and adsorption capacity of the mats. We focused on the adsorption of Pb2+, Cu2+ and Cd2+ from acidic solutions onto cellulose-TiO2/REC composite nanofibrous mats in multiple systems because the magnitudes of heavy metal concentrations in wastewater typically varied. The maximum total adsorption capacity of 69.81 mg/g was obtained by Cellulose-TiO2/REC2:1 nanofibrous mats. The composite nanofibrous mats successfully trapped TiO2 nanoparticles, and the obtained cellulose-TiO2/REC nanofibrous mats could be used to remove heavy metals from acidic wastewater.

Distinct Solute Removal Patterns by Similar Surface High-Flux Membranes in Haemodiafiltration: The Adsorption Point of View

Introduction: Haemodialysis (HD) allow depuration of uraemic toxins by diffusion, convection, and adsorption. Online haemodiafiltration (HDF) treatments add high convection to enhance removal. There are no prior studies on the relationship between convection and adsorption in HD membranes. The possible benefits conferred by intrinsic adsorption on protein-bound uraemic toxins (PBUTs) removal are unknown. Methods: Twenty-two patients underwent their second 3-days per week HD sessions with randomly selected haemodialysers (polysulfone, polymethylmethacrylate, cellulose triacetate, and polyamide copolymer) in high-flux HD and HDF. Blood samples were taken at the beginning and at the end of the treatment to assess the reduction ratio (RR) in a wide range of molecular weight uraemic toxins. A mid-range removal score (GRS) was also calculated. An elution protocol was implemented to quantify the amount of adsorbed mass (Mads) for each molecule in every dialyser. Results: All synthetic membranes achieved higher RR for all toxins when used in HDF, specially the polysulfone haemodialyser, resulting in a GRS = 0.66 ± 0.06 (p < 0.001 vs. cellulose triacetate and polyamide membranes). Adsorption was slightly enhanced by convection for all membranes. The polymethylmethacrylate membrane showed expected substantial adsorption of β2-microglobulin (MadsHDF = 3.5 ± 2.1 mg vs. MadsHD = 2.1 ± 0.9 mg, p = 0.511), whereas total protein adsorption was pronounced in the cellulose triacetate membrane (MadsHDF = 427.2 ± 207.9 mg vs. MadsHD = 274.7 ± 138.3 mg, p = 0.586) without enhanced PBUT removal. Discussion/Conclusion: Convection improves removal and slightly increases adsorption. Adsorbed proteins do not lead to enhanced PBUTs depuration and limit membrane efficiency due to fouling. Selection of the correct membrane for convective therapies is mandatory to optimize removal efficiency.

Insight the roles of loosely-bound and tightly-bound extracellular polymeric substances on Cu2+, Zn2+ and Pb2+ biosorption process with Desulfovibrio vulgaris

The aim of this study is to explore the fate and mechanism of metal cations of biosorption in the Desulfovibrio vulgaris system (including bacterial cells and secreted loosely-bound extracellular polymeric substances (LB-EPS) and tightly-bound extracellular polymeric substances (TB-EPS)). The relative contribution of EPS (TB-EPS and LB-EPS) to the adsorption of three metal cations is much greater than that of bacterial cells, and the adsorption capacity of Pb2+ on EPS (TB-EPS and LB-EPS) is much greater than that of Cu2+ and Zn2+ (Pb2+ > Cu2+ > Zn2+). The order of absorption capacity was as follows: LB-EPS > TB-EPS > bacterial cells, the adsorption contribution of EPS (including TB-EPS and LB-EPS) to Cu2+, Zn2+ and Pb2+ accounted for total adsorption capacity was 82%, 83% and 86%, respectively. It was suggested that LB-EPS was the first reaction barrier of immobilization metal cations before metal cations was able to pass through EPS and react with cells. The adsorption process was dominated by complexation and electrostatic interaction. The three-dimensional excitation-emission matrix (3D-EEM) identified two main fluorescence peaks of the aromatic and tryptophan protein-like substances in EPS. According to the synchronous fluorescence spectra, the tryptophan protein-like substances were gradually quenched with increased metal cations concentrations, which the quencher mechanism is dynamic quenching. The findings of this work are significant to reveal the fate of Cu2+, Zn2+ and Pb2+ during its sorption process onto Desulfovibrio vulgaris, and provide useful information of the interaction between Desulfovibrio vulgaris and its secreted EPS with metal cations.

Unusual Maximum in the Adsorption of Aqueous Surfactant Mixtures: Neutron Reflectometry of Mixtures of Zwitterionic and Ionic Surfactants at the Silica-Aqueous Interface.

The adsorption of two zwitterionic surfactants, dodecyldimethylammonium propanesulfonate (C12PS) and dodecyldimethylammonium carboxybetaine (C12CB), and of their mixtures with the cationic dodecyltrimethylammonium bromide (C12TAB) and the anionic sodium dodecylsulfate (SDS) at the silica-water interface has been studied by neutron reflection (NR). The total adsorption, the composition of the adsorbed layer, and some structural information have been obtained over a range of concentrations from below the critical micelle concentration (CMC) to about 30× the mixed CMC. The adsorption behavior has been considered in relation to the previously measured micellar equilibrium of these mixtures in their bulk solutions and their adsorption at the air-water interface. C12CB adsorbs cooperatively close to its CMC to form an almost complete bilayer on its own, whereas C12PS adsorbs more weakly in a fragmented bilayer structure. Although SDS does not normally adsorb at the silica-water interface, SDS adsorbs strongly and cooperatively with C12PS at fractional SDS compositions up to about 0.5. This cooperativity is lost when the adsorbed fraction of SDS rises above about 0.5. At this point, adsorption drops sharply, creating an unusual maximum in the variation of adsorption with a total concentration above the mixed CMC. Neither the increase in cooperativity nor the subsequent decline in adsorption results directly from variations of the independently determined monomer concentrations in the bulk solution. The adsorption maximum is predominantly the effect of strong cooperative interaction, possibly accompanied by partial segregation of SDS within the layer, followed by charge repulsion from the surface. Although the solution aggregation and adsorption at the A-W interface are similar for SDS with C12CB, the addition of SDS to C12CB at the silica-water interface promotes the opposite behavior to that of SDS with C12PS, and SDS simply disrupts the cooperative binding of C12CB. Unlike SDS, the cationic surfactant C12TAB adsorbs on silica. It therefore coadsorbs at the SiO2-W interface with either C12CB or C12PS. However, in neither case is there any pronounced cooperativity and, even though the presence of C12TAB might be expected to favor adsorption, the adsorption is generally unexpectedly low.

Effective adsorption of bisphenol A from aqueous solution over a novel mesoporous carbonized material based on spent bleaching earth.

In this study, the novel mesoporous carbonized material (HSBE/C) was prepared from clay/carbon composite (SBE/C) treated with hydrofluoric acid (HF) for the first time, and was employed to efficiently adsorb bisphenol A (BPA) in water. Specifically, SBE/C was derived from the pyrolysis of spent bleaching earth (SBE), an industrial waste. HF removed SiO2 from SBE/C and increased the specific surface area of HSBE/C (from 100.21 to 183.56 m2/g), greatly providing more adsorption sites for enhanced BPA adsorption capacity. The Langmuir monolayer maximum adsorption capacity of HSBE/C (103.32 mg/g) was much higher than the commercial activated carbon (AC) (42.53 mg/g). The adsorption process by HSBE/C followed well with the Freundlich isotherm model and the pseudo-second-order kinetic model and also was endothermic (ΔH0 > 0) and spontaneous (ΔG0 < 0). Based on the systematic characterization and factor experiment (temperature, dosage, initial pH, co-existing ions), BPA adsorption mechanism by HSBE/C likely included the hydrogen bonding, electrostatic interaction, and hydrophobic interaction. Moreover, there was no secondary pollution during the total adsorption process. Extraordinary, HSBE/C manifested stability by NaOH desorption regeneration. This study provides a new sight for application of waste-based materials as the promising adsorbents in the treatment of endocrine disruptors.

Characteristics and quantification of mechanisms of Cd2+ adsorption by biochars derived from three different plant-based biomass

The physicochemical properties of biochars derived from rice straw, eucalyptus leaves, and vetiver grass pyrolyzed at 400 °C were investigated. It was found that rice straw biochar (RSB) may possess more acidic functional groups than eucalyptus leaves biochar (ELB) and vetiver grass biochar (VGB) while the specific surface area of VGB was the largest. Cd2+ adsorption characteristics by the three biochars were established under the effects of time, initial pH and concentration of solution. Maximum adsorption capacities of RSB, ELB, and VGB calculated by Langmuir model were 57.87 mg/g, 50.21 mg/g, and 44.09 mg/g, respectively, reflecting adsorption mechanisms may be dominated by chemical reaction than physical interaction. SEM-EDS, XRD, FTIR and XPS were employed before and after adsorption to qualitatively explore possible adsorption mechanisms of the three biochar. It was found that precipitation, ion exchange, complexation and cation π interaction occurred in all the biochars. The relative contribution of the four main mechanisms to total adsorption capacity was quantitatively determined, suggesting precipitation, ion exchange, and cation π interaction were dominated for the three biochar, while complexation accounted for an insignificantpart. This study clearly demonstrated mineral constituents of biochar had significant effects on Cd2+ adsorption by plant-based biochars, shedding some light on their future application.

Characteristics, adsorption behaviors, Cu(II) adsorption mechanisms by cow manure biochar derived at various pyrolysis temperatures

With the aims of exploring the effectiveness of Cu(II) adsorption performed by cow manure biochars (CMBCs) for the treatment and recycling of livestock wastes, the physicochemical characteristics and Cu(II) adsorption behaviors of CMBCs at various pyrolysis temperatures (T) were analyzed. CMBCs displayed surface heterogeneity and the dominant Cu(II) adsorption reactions were chemical adsorption, including mineral co-precipitation and cations exchange, was account for 93.75% − 97.01% of the adsorption contribution. Pearson correlation analysis and quantitative analysis showed that the adsorption capacity of co-precipitation (Qcp) and cations exchange (Qci) were significantly positively correlated with ash content and cations exchange capacity (p < 0.01), respectively. The quantitative relationships between total adsorption capacity (Qt), Qcp or Qci and T are Qt = 54.01 + 0.39exp(0.0051 T), Qcp = 71.80–101.91exp(−0.0024 T), Qci = 12.25 + 311.73exp(−0.0093 T) and Qt = 0.93 Qci + 0.91 Qcp + 7.70.

Oxidized eucalyptus charcoal: a renewable biosorbent for removing heavy metals from aqueous solutions

In this study, a comparison between charcoal produced from Eucalyptus urograndis modified and unmodified with HNO3 on the adsorption capacity of metals (Cu(II), Cd(II), and Ni(II)) in aqueous solutions was performed. The modification was performed using charcoal from the wood of a hybrid of Eucalyptus urophylla x Eucalyptus grandis (commonly referred to in Brazil as Eucalyptus urograndis). The charcoal was produced at a final temperature of 450 °C. Nitric acid was the oxidizing agent, employed at a concentration of 12.5% (v/v) and a reaction time of 3 h. The materials were characterized and compared using thermogravimetric analysis, thermogravimetric index, specific surface area analysis, scanning electron microscopy, elemental analysis, and point of zero charge. Studies of the process factors (contact time, mass, ideal pH), adsorption isotherms (Langmuir and Freundlich), and the thermodynamics of the process were also carried out. Treatment with nitric acid altered the elemental composition of charcoal, and functional groups, like carbonyl groups, were added to the surface, which caused a significant increase in total adsorption capacity (from 114.27 to 310.53 mg g−1 in a solution with a mix of metals). The model that best fit the data was Langmuir, and the maximum removal of Cu(II) ions was 96%, and occurred at pH 5, at 318 K, with a dose of biosorbent equal to 0.4 g 50 mL−1 of solution and equilibrium contact time of 30 min. Thermodynamic parameters suggested that adsorption occurred spontaneously and occurred through the ion exchange and electrostatic interaction mechanisms. In systems with the presence of more than one metal ion, the total adsorption capacity increased.

Enhancement of Hydrothermal Stability and CO2 Adsorption of Mg-MOF-74/MCF Composites.

Hierarchical porous composite Mg-MOF-74/MCFs were successfully synthesized using a simple and facile method under in situ solvothermal conditions. Textural structures and morphologies of the composites were characterized by X-ray diffraction (XRD), N2 adsorption–desorption isotherms, and scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results demonstrate that a large amount of nanosized Mg-MOF-74 particles is incorporated into the pores of mesocellular siliceous foams (MCFs) without remarkable aggregation and the composites possess microporous and mesoporous characteristics of both components. In addition, CO2 adsorption properties of the composites were tested in a fixed bed with/without hydrothermal treatment. The total CO2 adsorption capacities were calculated by breakthrough curves. The CO2 adsorption capacity of the composites reaches 1.68 mmol/g, which is smaller than that of pristine Mg-MOF-74. However, the total CO2 adsorption capacity of the composites after hydrothermal treatment reaches 2.66 mmol/g, which is larger than that of Mg-MOF-74 (2.39 mmol/g) under the same condition. XRD patterns and SEM images of the composites demonstrate that the hydrothermal stability and CO2 adsorption performance of the composites were improved compared with those of pristine Mg-MOF-74 after hydrothermal treatment.

Electro-Fenton degradation of a ternary pharmaceutical mixture and its application in the regeneration of spent biochar

This study proposed an integrated valorisation system, by combining adsorption and electro-Fenton processes for fast and effective micropollutant remediation of a complex pharmaceutical mixture. The pharmaceuticals venlafaxine, fluoxetine and trazodone, commonly detected in the environment (river water and sediment), were selected in this study as target pollutants. Initially, the electro-Fenton degradation process of the ternary mixture was optimised. For this, a Box-Behnken experimental design was used and the degradation of each pollutant, as a response function, was evaluated using three key operational process parameters (iron concentration, current intensity and solution pH). The pharmaceutical mixture was removed by total adsorption onto the biochar, the regeneration of which was then carried out under the optimal electro-Fenton conditions (0.24 mA, 0.33 mM Fe2+ and pH 3.2). In addition, different options in relation to the presence of iron were considered: i) iron dissolved in aqueous solution; ii) iron supported on the biochar; iii) no addition of iron (“self-cleaning”). The results confirmed that the natural content of iron in the biochar was enough to catalyse the electro-Fenton regeneration. The adsorption-electro-Fenton regeneration process was repeated over several cycles with no reduction in the efficiency of either process. Finally, this combination (adsorption and electro-Fenton process) was tested using an aqueous matrix from a wastewater treatment plant.

DYNAMIC STUDY OF ADSORPTION PERFORMANCE FOR REMOVING AS (V) THROUGH POLYACRYLONITRILE (PAN) FIBER USING ASPEN ADSORPTION

Arsenic is known to be one of the most significant and severe inorganic pollutants in drinkable water globally. Many important techniques have been read for better results, such as ion-exchange, flocculation, precipitation, coagulation, adsorptions and other membrane technologies , when complying with the MCL (maximum contaminant level), Arsenic(V) around 10¼g / l in drinkable water) developed worldwide by the major World Health Organization, These available water treatment technologies are applicable; adsorption has proven to be a favorable and efficient technology for the removal of Arsenic from any form of water with dissimilar concentrations. In this analysis, Arsenic (As (V)) removal from water that studied by the packed bed column by modeling and simulation using iron ore adsorbent in the ASPEN ADSIM V11 software. The various effects on the efficiency of the adsorption column, such as bed height, feed-flow rate and the initial Arsenic concentrations of different operating parameters, were studied theoretically. Experiments were performed in specific cases to verify the results. Bed-depth greater then more Arsenic (v) are adsorbed and the Arsenic removal was achieved 100 % at a bed-height of 29.0 cm for simulation. The percentage of Arsenic removal, as well as the total adsorption of Arsenic increase with the decrease in flow rate, it is observed that when the bed height is increased the service time of adsorption bed also increases. The results showed that the design parameters such as adsorbent bed depth and column diameter, together with operating parameters such as Arsenic inlet concentration, have great effects on the overall column efficiency.

Order and disorder in the adsorption model of repulsively interacting binary mixtures on triangular lattices: theory and Monte Carlo simulations.

The problem of interacting binary mixtures adsorbed on triangular lattices has been studied by means of ground-state (GS) calculations, Monte Carlo (MC) simulations and exact counting of configurations on finite cells [the so-called cluster-exact approximation (CA)]. We focus on the case of repulsive intraspecies couplings and null interspecies interaction, where a rich variety of ordered phases is found in the adsorbed layer. Each surface structure is separated from a disordered state by a phase transition occurring at a finite temperature. The ordered phases are identified by means of GS analysis, and their dependence on temperature is studied by MC simulations and CA. Total and partial adsorption isotherms are obtained for values of the lateral interactions in the different regions of the phase diagram. MC results are compared with CA calculations. A very good coincidence is obtained between both methods, supporting the validity of the exact counting of states on finite cells as an adequate approach to describe the behavior of multicomponent competitive adsorption with adsorbate-adsorbate interactions.

Understanding of mechanisms of organohalogens removal onto mesoporous granular activated carbon with acid-base properties

Adsorptive removal of 4-chlorophenol, 4-bromophenol and 4-iodophenol from aqueous solutions by commercial granular activated carbon (GAC) was studied. The main important characteristics of GAC were investigated: SBET 1010 m2/g, pHPZC 5.2, total acidity 0.3 mmol/g and total basicity 0.6 mmol/g. The favourable adsorption conditions were: pH 5–10, agitation time 240 min and adsorbent dosage 2 g/L. The maximum adsorption capacity of 4-halogenphenols was determined from adsorption isotherms: 168.5 mg/g for 4-chlorophenol, 151.7 mg/g for 4-bromophenol and 61.5 mg/g for 4-iodophenol. Experimental kinetic curves followed pseudo-second order for all compounds investigated. It was found that the Langmuir isotherm model is the most appropriate to describe adsorption of all organohalogens on the GAC surface. Desorption studies determined that the best desorbents were concentrated acetic acid, ethanol and 1 M potassium hydroxide. Elucidation of adsorption mechanism showed that the elimination of 4-halogenphenols was caused by film diffusion, H-bonding and esterification reactions. The contribution of each mechanism in total adsorption was also estimated. It was shown that halogen atom had significant influence on adsorption mechanism. The present work offers a novel insight of the adsorption mechanism between GAC and other phenolic compounds.