Papers by Keyword: Adsorption Capacity

Abstract: This study focused on the oil absorption and carbonization regeneration properties of expanded graphite (EG) prepared from commercial expandable graphite as an oil absorbing material for different oils. The specific surface area of the prepared EG sample was 37.15 m²/g, and the oil absorption was as high as 76 g/g. More importantly, the prepared expanded graphite had excellent recyclability and good carbonization regeneration performance. Even after 5 cycles, the adsorption capacity remained above 80%. The regenerated EG sample regained a high oil absorption capacity of 44.64g/g. This article has important guiding significance for promoting the large-scale practical application of expanded graphite oil absorbing materials.

Abstract: In this study, we utilized an adsorbent based on rice straw for reducing hexavalent chromium ions (Cr (VI)) in an aqueous solution. The rice straw as adsorbent raw material was washed, dried, and powdered. Rice straw powder was heated at 450°C for 2 hours to obtain rice straw adsorbent. The adsorbent was activated with 1M H₃PO₄ for 4 hours. Characterization of the adsorbent was done using Fourier Transform Infra-Red (FTIR) method. FTIR spectra showed the presence of hydroxy, carboxylic, aromatic, and ether groups on the surface of the rice straw and the made adsorbent. The reduction of Cr (VI) ions in aqueous solutions was carried out using the adsorption batch method. The adsorption process was conducted in various the Cr (VI) solutions pH for 1-5 and variations in contact time for 5-720 minutes. The highest percentage reduction of Cr (VI) reached 66.90%. It has occurred at pH 2 and equilibrium at 600 minutes of contact time.

Abstract: One step polyacrylamide gel method was used to synthesize the ZnO/MgO adsorbents and the adsorption behavior with Congo red (CR) from wastewater was extensively investigated. Various advanced techniques were applied to confirm the ZnO/MgO adsorbents consist of Zn, C, Mg and O elements and do not contain any other impurity elements. With the increase of MgO content, the morphology of ZnO/MgO adsorbent changes from the agglomeration of large particles to evenly dispersed fine particles and then to icicle structure. Results demonstrated that the adsorption process of ZnO/MgO adsorbents was significantly affected by the change in initial dye solution pH, initial adsorbent dosage, contact time and reaction temperature. The optimum pH, adsorbent dosage, contact time and reaction temperature is 9.81, 2 g /L, 65 min and 293 K, respectively. The maximum adsorption capacity of ZnO/MgO (nZnO:nMgO = 8:2) adsorbents (295.138 mg/g) for the adsorption of CR dye was approximately double that of previous reports (125 mg/g). The adsorption equilibrium data are well fitted by the Freundlich and Langmuir isotherm models. Thermodynamic studies indicate that the adsorption process of ZnO/MgO adsorbents is an exothermic process. Based on the experimental and theoretical analysis, the adsorption mechanism for the ZnO/MgO adsorbents consisted of hydrogen bonding, n-π interaction and electrostatic interaction. The present work pioneers the potential application of ZnO/MgO adsorbents for the adsorption of CR dye and further provides experimental evidence for the synthesis of other adsorbents.

Abstract: Adsorption of Au(III) and Cu(II) by mangosteen rind adsorbent had been carried out. Mangosteen rind has several functional groups including –OH phenolics, ‒C=C‒ aromatics, and ethers. Dried mangosteen rind which was obtained from maceration was used to determine Point of Zero Charge (PZC). The most effective pH adsorption was determined by mixing adsorbent with Au(III) or Cu(II) solutions with various pH. The adsorption capacity was affected by the interaction between adsorbent and adsorbate. The solid adsorbent before and after interaction was characterized by FTIR, XRD, and microphotography. The PZC pH value of adsorbent was 3.7 while the optimum pH for Au(III) and Cu(II) were at pH 2 and pH 5, respectively. The adsorption capacity (q_max) value was 333.33 mg/g by following the Langmuir isotherm equation. The crystalline structure of adsorbent was analyzed using XRD and gave 4 peaks characteristics of gold metal on 2ϴ = 38º, 44º, 64º, and 77º after adsorption which indicated the reduction of Au(III) ions into Au(0).

Abstract: The aim of this study is to investigate the effect of natural zeolites characteristics on the adsorption capacity of Pb²⁺ from an aqueous environment. The used natural zeolites were originated from 3 regions in Indonesia. i.e. Bayah, Banten (coded as ZB) and two samples from South Lampung (coded as ZL-1 and ZL-2) and Nanggung, Bogor (ZN). The characteristics of each natural zeolite were evaluated through a series of detailed analysis including XRD, FTIR, XRF, SEM and N₂ physisorption. It was revealed that ZB, ZL-1 and ZL-2 were dominated by clinoptilolite (HEU) frameworks while the major phase of ZN was mordenite (MOR) type. From XRF data, the three natural zeolites (ZB, ZL-1 and ZN) possessed a comparable Si/Al ratio (ca. 5.5 to 6) whereas ZL-2 had slightly lower Si/Al ratio (ca. 4). We found that, at comparable Si/Al ratio, clinoptilolite frameworks has a higher adsorption capacity of Pb²⁺ compared to that of mordenite due to the compatibility of Pb²⁺ inside the pores of clinoptilolite. Lower Si/Al ratio of natural zeolite tended to show higher adsorption capacity of Pb²⁺ since the net charge of zeolite frameworks became more negative. These two factors, the framework type and the Si/Al ratio, are significant for the adsorption capacity. Another factor, i.e. surface area, had no certain effect on the adsorption capacity in this case.

Abstract: The volatile organic compounds (VOCs) contribute to serious air pollution problems in Viet Nam. Many studies have investigated in air quality monitoring and treatment, in order to determine the average concentrations of Benzene, Toluene, Ethylbenzene and Xylene (BTEX). Carbon nanotubes (CNTs) have been widely used as adsorbent in environmental treatment, especially for VOCs. This paper aims to determine the adsorption capacity of multiwalled carbon nanotubes for removal of BTEX from air samples. In preliminary study, the effects of various parameters during adsorption experiments were monitored such as flow rate, temperature and BTEX concentrations in air samples. The equipment for BTEX removal was developed by our research team consisting of filter columns, air sample bags, adsorption cartridge. The air samples containing BTEX were conducted directly through a cartridge packed with adsorbent. The adsorption experiments were carried out under various operating conditions such as temperature (30 - 40°C), gas concentration (0,57 - 4,77 mg/L) and the gas flow rate (10 - 90 mL/min). In addition, isotherm studies of CNTs for BTEX removal were achieved by using Langmuir and Freundlich models. The results showed that the experimental parameters were optimized at a flow rate of 30 mL/min and an ambient temperature at 30°C. The adsorption capacity of CNTs increased proportionally with BTEX concentrations. The specific affinity of CNTs for BTEX from air samples was in order of X > E > T > B. The experimental isotherm data were well-fit with the Langmuir model for Benzene and Xylene removal, and the Freundlich model for Toluene and Ethylbenzene adsorption. The CNTs presented highly potential application for BTEX adsorption thanks to their microporous structure and high surface area.

Abstract: The lithium ion-sieve precursor was prepared with LiOH and Mn (CH₃COO)₂ as the starting reagents, H₂O₂ as the oxidant and ethanol solution (volume percent 2.5%) as solution by combination of sol-gel, hydrothermal and low-temperature solid state methods, and then changed into lithium ion-sieve after eluting Li⁺ by the mixture of HCl and Na₂S₂O₈ solution. The influence of synthetic conditions on the structures and adsorption properties of lithium ion-sieve was investigated in detail. The results suggest that the pure phase lithium ion-sieve can be synthesized when Li/Mn molar ratio is 3/1, 3.2mL H₂O₂ is added after LiOH and Mn (CH₃COO)₂ react for 36h and the heat treatment way of programmed temperature from 410°C (2h) to 510°C (3h) is adopted in the progress of solid state reaction. The loss rate of dissolved Mn is less than 2.5% during pickling Li⁺. And the highest adsorption capacity can achieve 20.5mg/g.

Abstract: The progress of adsorption capacity-enhancing modified manganese mineral, as well as the optimal conditions on which the adsorption of modified natural manganese mineral is conducted, are discussed and summarized in this paper. Moreover, the optimal parameters of the adsorption of Cu2+, Ni2+, and As (V) by using natural manganese mineral are respectively presented and the adsorption capacity is compared.

Abstract: According to the practice of city gas odorization, the technological thought that the diffusion behavior of natural gas in soil was indirectly reflected by the adsorption capacity of tetrahydrothiophene (THT) as an odorant of natural gas in soil was put forward and explored. The adsorbed amount of THT in soil samples by gas chromatography-mass spectrometry (GS-MS) with purge and trap was determined. The impact of four parameters (namely gas leakage, water content, particle size and texture of the soil) on the adsorption properties of soil was then quantitatively analyzed. The experimental results showed that at initial stage of adsorption, the adsorption capacity of THT in soil sample was linear positively correlated with gas leakage and was negatively correlated with water content of the soil and there were no significant differences between particle size and texture of the soil and the amount of THT.

Abstract: The main objective was to synthesize in the laboratory and characterize the molecular sieve MCM-41. This study has a strong experimental character. The hydrothermal synthesis was performed at 100 ° C for a period of 7 days. The resulting materials were characterized by XRD, EDX, Adsorption Capacity and the Foster Swelling test. Through XRD verified the formation of mesoporous structure. Different organic solvents, namely gasoline, diesel and kerosene were used. The Foster Swelling Test results indicated that the affinity of molecular sieve MCM-41 occurred in the treated clay tested in all organic solvents (gasoline, diesel, kerosene), without and with agitation.