Chemical Properties Of Adsorbents Research Articles

Adsorption behavior of carboxy- and amine-terminated magnetic beads for patulin: Batch experiments in aqueous solution and apple juice

Patulin (PAT) is a highly water soluble, heat resistant and toxic fungal metabolite mostly contaminating apple juice. Due to its serious health effects, its removal from foodstuffs is required to ensure food safety. In this study, carboxy- and amine-terminated iron oxide spheres (Fe3O4-COOH and Fe3O4-NH2) were investigated for their adsorbing capacity of PAT in both aqueous solution and apple juice, and evaluated for being an effective detoxifying agent for PAT. The physical and chemical properties of adsorbents were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM). The maximum adsorption capacities Fe3O4-COOH and Fe3O4-NH2 for PAT obtained at 25 °C, pH 6 for 5 h were 0.206 mg/g and 0.104 mg/g, respectively. Best fitting adsorption isotherm and kinetics models of PAT adsorption process were Hill isotherm (Radj2 = 0.985) and pseudo-second kinetic models (Radj2 > 0.99) for carboxy groups and Langmuir isotherm (Radj2 = 0.974) and pseudo-second kinetic models (Radj2 > 0.99) for amine groups on the surface of adsorbents. These models with the experimental results confirmed the physical adsorption process, while thermodynamic analysis indicated that adsorption process was spontaneous and endothermic between PAT and both adsorbents. Reusability study showed the effective removal of PAT at four cycles by both adsorbents. This study indicated that carboxy- and amine-terminated magnetic spheres have promising potentials in PAT removal from both aqueous solution and apple juice without affecting quality parameters of juice.

Combination of X-ray powder diffraction and adsorption calorimetry for the characterization of calcium exchanged LTA zeolites

While structural and chemical properties of adsorbents are largely known, energetic properties are mostly not known yet. In cation exchanged zeolites, the type, number, and position of cations have a major influence on energetic properties. Therefore, the energetic values of cations were investigated systematically on LTA zeolites. In these CaNaA materials, Na+-cations were selectively replaced by Ca2+-cations with calcium exchange rates between 8.7% and 92.1%. The cation sites were determined by crystal structure analysis of X-ray powder diffraction data (XRPD). Rietveld analysis showed the sequence of emptying Na+-cations from the various cation sites and the occupancy sequence of Ca2+-cations as a function of the exchange rate. In addition, sensor gas calorimetry was used to measure the heat of adsorption using methane as a sample molecule. The results show an increase in capacity and heat of adsorption up to an exchange rate of 68.6%. At higher exchange rates, the capacity and heat of adsorption decrease again. Characteristic plateaus of the heat of adsorption were found for all materials. By combining XRPD and calorimetry, the plateaus of the heat of adsorption were assigned to the different cation positions inside the zeolite cages and the respective energetic contributions were determined. Ca2+-cations represent energetically more valuable adsorption sites compared to Na+-cations. Furthermore, differences in the energetic values of the various cation sites were identified. It was also found, that the interactions with the zeolite framework provide the largest contribution.

Enhanced adsorptive removal of phosphate from aqueous solution by activated sand/metal layered double hydroxides

ABSTRACT In the present study, Mg-Fe and Ni-Fe layered double hydroxides have been examined to enhance the uptake capacity of activated sand as low-cost adsorbents for adsorption of phosphate. The physical and chemical properties of adsorbents were investigated by X-ray diffractometer (XRD), X-ray fluorescence (XRF) spectrum, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis. The best efficiency of both adsorbents was obtained at the optimum condition of initial phosphate concentration: 1000 mg/L, adsorbent dose: 1 g, pH: 7–7.5, and a temperature of 298 K. The equilibrium isotherm studies show that the best result was attained in the Langmuir model for phosphate; therefore, homogeneous adsorption is dominated, which was also emphasised by three-parameter-isotherm models. The maximum adsorption capacity for functionalised sand with Mg-Fe and Ni-Fe layered double hydroxides were obtained 69.47 and 66.64 mg/g, respectively. The kinetic data fit well with the pseudo-second-order kinetics and demonstrate that the porous diffusion effectiveness is over film diffusion. Thermodynamic parameters evoke the feasibility of the adsorption process as well as the positive influence of temperature on adsorption.

Production and characterisation of adsorbents synthesised by hydrothermal carbonisation of biomass wastes

Surface structure and chemical properties of adsorbents are important factors required to understand the mechanism of adsorption. The purpose of this study was to produce hydrochars from biomass using hydrothermal carbonisation (HTC) and to analyse their sorption capacities. The biomass used in this study were coco-peat (CP), coconut shell (CS), eggshell (ES), rice husk (RH) and lemon peel (LP). The operating conditions for HTC were 200 °C and 20 h residence time. The characterisation methods consisted of Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Fourier Transform Infrared Ray (FTIR) Spectroscopy, and Brunauer, Emmett and Teller (BET). The results showed that HTC improved the sorption capacities of the biomass wastes. It was found that hydrochars were crispy and flaky with more micro- and meso-porous structures, indicating that lignin and other components were denatured due to carbonisation. This led to the creation of more active sites for sorption and pollutant binding. The hydrochars showed a percentage increase in carbon content and a decrease in oxygen content with traces of other elements, compared to their corresponding raw biomass. The major functional groups identified were –OH and –COOH. The surface area of the hydrochars which include CP (2.14 m2/g), CS (14.04 m2/g), ES (0.50 m2/g), RH (15.74 m2/g), and LP (6.89 m2/g) were significantly improved compared with those of the raw biomass. The study showed that the hydrochars produced from the biomass wastes have the potential to be used as adsorbents.

Graphene-like porous carbon nanostructure from Bengal gram bean husk and its application for fast and efficient adsorption of organic dyes

Graphene-like porous carbon nanostructure (BGBH-C-K) is prepared using the Bengal gram bean husk (BGBH) as agro-waste biomass via alkali-activation. Abundance of micropores in the BGBH-C-K furnished high pore volume (0.834 cm3.g−1) and surface area (1710 m2.g−1). The π-electron rich graphitic domains, remarkable textural properties, thorough distribution of micro and meso pores, and presence of oxygen functionalities as deduced by HRTEM, XPS, FTIR, and N2 adsorption-desorption isotherm promise the potential of BGBH-C-K for adsorption of organic dyes. The experimental data revealed excellent adsorption capacity of BGBH-C-K for methylene blue (469 mg.g−1; cationic dye) and methyl orange (418 mg.g−1; anionic dye). The π-π interaction, hydrogen linkage, electrostatic interaction, and trapping of dye molecules on the structural defects facilitate the adsorption of organic dyes by the BGBH-C-K. The adsorption capacity and efficiency are collectively monitored by textural and chemical properties of adsorbents along with size, shape, and charge of dye molecules. The finding revealed the remarkable capability of BGBH-C-K as a dye scavenger for efficient removal from industrial wastewater.

Removal of Malachite Green Dye from Aqueous Solution by Adsorption Using Modified and Unmodified Local Agriculture Waste

Local agriculture waste (Shell’s seeds of Ziziphus spina christi) (SZC), in both its unmodified SZC and acid-modified (SZC-AC) forms, was investigated for its potential use as a low-cost adsorbent for the removal of malachite green (MG). Characterization of the adsorbents was carried out using scanning electron microscope (SEM), Fourier transforms infra-red spectroscopy (FTIR), pH surface, Boehm titration, including, other physical and chemical properties of adsorbent. The effects of initial dye concentration, contact time, solution of pH, temperature and adsorbent dosage were investigated in detail by batch adsorption experiments. For the adsorption of MG were fitted using Langmuir and Freundlich isotherm models, equilibrium isotherms were applicable with maximum monolayer adsorption capacity wear 48.780 mg/g and 370.370 mg/g for the raw shells seeds of Ziziphus spina christi (SZC) and the activated carbon prepared from shells seeds by sulphuric acid SZC-AC, respectively. Kinetics studies showed that both followed the pseudo-second order. Thermodynamics studies indicated that the adsorption of MG was spontaneous on SZC and SZC-AC, and the reactions were endothermic and exothermic, respectively. The proposed adsorbents were successfully applied to the removal of malachite green dye from different water samples with a recovery % >95% and a relative standard deviation (RSD%) <3%.

Gold recovery from very dilute solutions from a mine in closing process: Adsorption-desorption onto carbon materials

The aurocyanide complex recovery by precipitation with zinc decreases when gold concentration drops to <20μgL−1. Therefore, a technology capable of recovering gold from very diluted solution is necessary. Adsorption and desorption experiments were carried out with real solutions in batch and in continuous processes to determine the gold adsorption capacity and rate onto two activated carbons (AC). The results showed that AC F400 and CSC removed 86 and 81μgg−1, respectively, at pH11 and Ce of 10μgL−1 in about 4h. Whereas desorption test by NaOH and CN− showed a gold recovery of up to 86%. These experiments were correlated to the textural and chemical properties of adsorbents and to the chemical composition of samples from a heap leach process. AC is a highly efficient and selective adsorbent for gold cyanide solutions when gold is present in very low concentration (<12μgL−1).

Potential of Using Surfactants to Enhance Ammonium and Nitrate Adsorption on Rice Husk and Its Biochar

Inorganic nitrogen fertilizers are widely and heavily used in agriculture. Leaching of these fertilizers is a cause of eutrophication in water bodies. This study examines the use of rice husk and its biochar, their efficiency in adsorption of ammonium and nitrate and the potential of using surfactants, sodium dodecyl benzenesulfonate (SDBS) and cetyl trimethyl ammonium bromide (CTAB), to increase adsorption. Physical and chemical properties of adsorbents were examined through BET, SEM-EDX, and CEC value, respectively. The equilibrium batch adsorption was conducted. The result showed that rice husk was lower in surface area, total pore volume, pore diameter, silica and oxygen content, and CEC value as compared to biochar. Rice husk adsorbed nitrate well while rice husk biochar adsorbed ammonium ions better. The adsorption patterns of both ammonium and nitrate were well explained by Freundlich’s isotherm and are primarily attributed to chemical charge sorption. Both adsorbents could adsorb surfactants through Van der Waals forces between the long chain of surfactant and organic fraction on the surface of rice husks, exposing the charging head for ionic pollutant adsorption. Either SDBS or CTAB-modified rice husk and its biochar could enhance the adsorption of ammonium and nitrate.

개질 수소 정제용 PSA 공정을 위한 CO 흡착제의 성능 평가

Natural gas reformed hydrogen is used as a fuel of fuel cell vehicle, PSA process is used for the purification of reformed hydrogen. In this study, the performance of CO adsorbent in PSA process was evaluated. Zeolite adsorbents used in the commercial PSA process is used. The physical and chemical properties of adsorbents were characterized using BET apparatus, XRD, and FE-SEM. The breakthrough apparatus modified from GC was used for the CO breakthrough experiment, the quantitative analysis of CO adsorption capacity was performed using CO breakthrough curve. Zeolite 10X and 13X showed superior CO adsorption capacity than activated alumina. The CO adsorption capacity of zeolite 10X is more than twice of zeolite 13X even the BET surface area is low. It seems that the presence of <TEX>$Ca^{2+}$</TEX> cation in zeolite 10X is beneficial to the adsorption of CO.

Single, competitive, and dynamic adsorption on activated carbon of compounds used as plasticizers and herbicides

The main aim of this study was to investigate the single, competitive, and dynamic adsorption of phthalic acid (PA), bisphenol A (BPA), diphenolic acid (DPA), 2,4-dichlorophenoxy-acetic acid (2,4-D), and 4-chloro-2-methylphenoxyacetic acid (MCPA) on two activated carbons with different chemical natures and similar textural characteristics. The adsorption mechanism was also elucidated by analyzing the influence of solution pH and ionic strength. The activated carbons demonstrated high adsorption capacity to remove all micropollutants due to the presence of active sites on their surfaces, which increase dispersive interactions between the activated carbon graphene layers and the aromatic ring of pollutants. The adsorption capacity of the activated carbons increased in the order: DPA<BPA<PA<2,4-D<MCPA, which is directly related to: i) molecular size of pollutants; ii) chemical structure of pollutants, and iii) chemical properties of adsorbents. In most cases, the adsorption of contaminants is favored at acid pH (pH<5) due to the establishment of attractive electrostatic interactions. In dynamic regime, the amount of pollutant adsorbed was much higher for PA, followed by DPA, and was approximately similar for BPA, 2,4-D, and MCPA. Finally, the amount of BPA and DPA adsorbed on activated carbon decreased by around 50% and 70% in the presence of DPA and BPA, respectively, indicating that both compounds are adsorbed on the same adsorption sites of the activated carbon.

Use of activated carbon prepared from Prosopis spicigera L. wood (PSLW) plant material for the removal of rhodamine 6G from aqueous solution

The removal of rhodamine 6G dye from aqueous solution using carbon prepared from cheaply available agro-product, Prosopis spicigera L. wood (PSLW), was investigated. This work involves studies of physical and chemical properties of adsorbent, batch sorption experiments, and continuous run in a packed column at laboratory scale. Optimum condition for rhodamine 6G dye adsorption on PSLW carbon was determined by varying pHs, adsorbate concentrations, contact time, adsorbent dosage, and temperature. Lower solution pH favored the adsorption of Rh 6G dye. Adsorption onto the surface, surface mass transfer, and pore diffusion of dye molecules were the main process involved in the removal of Rh 6G dye. The adsorption followed Langmuir isotherm and the maximum adsorption capacity was found to be 8.86 mg/g for an initial concentration of 30 mg/L at 30°C. Thermodynamic parameters indicated that the adsorption interaction was spontaneous and exothermic in nature. The column study was explained using Thomas model.

Adsorption of Pb(II) from aqueous solutions using activated carbon developed from Apricot stone

Low-cost activated carbon was prepared from Apricot stone material by chemical activation with sulphuric acid for the adsorption of Pb(II) from dilute aqueous solution. The activated carbon developed shows substantial capacity to adsorb Pb(II) from dilute aqueous solutions. The parameters studied include physical and chemical properties of adsorbent, pH, adsorbent dose, contact time and initial concentrations. The percent removal increased with pH from 1.5 to 5. The optimum pH required for maximum adsorption was found to be 6.0. Adsorption kinetics data were modeled using the pseudo-first and pseudo-second-order models. The results indicate that the second-order model best describes adsorption kinetic data. The isotherm equilibrium data were well fitted by the Langmuir and Freundlich models. The estimated maximum capacities of lead ions adsorbed by Apricot stone activated with sulphuric acid were 21.38mgg−1. The adsorbent derived from this material is expected to be an economical product for metal ion remediation from water and wastewater.

Studies on the removal of Pb(II) from wastewater by activated carbon developed from Tamarind wood activated with sulphuric acid

The low-cost activated carbon were prepared from Tamarind wood material by chemical activation with sulphuric acid for the adsorption of Pb(II) from dilute aqueous solution. The activated carbon developed shows substantial capacity to adsorb Pb(II) from dilute aqueous solutions. The parameters studied include physical and chemical properties of adsorbent, pH, adsorbent dose, contact time and initial concentrations. The kinetic data were best fitted to the Lagergren pseudo-first-order and pseudo-second order models. The isotherm equilibrium data were well fitted by the Langmuir and Freundlich models. The maximum removal of lead(II) was obtained 97.95% (experimental) and 134.22 mg/g (from Langmuir isotherm model) at initial concentration 40 mg/l, adsorbent dose 3 g/l and pH 6.5. This high uptake showed Tamarind wood activated carbon as among the best adsorbents for Pb(II).