Papers by Keyword: Adsorption

Abstract: This paper aims to investigate the adsorption of Cr (VI) by cross-linked magnetic hydroxamated chitosan (MHCTS). The adsorption experiments were carried out in batch systems. To determine the optimum condition of the adsorption, factors such as pH, reaction time, initial Cr (VI) concentration and adsorbent dosage were considered. The experimental results showed that MHCTS can adsorb Cr (VI) with high efficiency. Optimum adsorption was observed at pH 4.0, and the highest adsorption removal reached 99.2%. The equilibrium was established within 90 min. The process could be described by pseudo-first-order and pseudo-second-order kinetic model.

Abstract: As an agricultural waste available in large quantity in China, Orange peel was utilized as low-cost adsorbent to remove furadan from aqueous solution by adsorption. Pseudo-first-order, second-order models and intraparticle diffusion model were applied to analyze experimental data and thus elucidated the kinetic adsorption process. The high values of correlation coefficients showed the data conformed well to the pseudo-first-order rate kinetic model over the initial stage of the adsorption processes. The plots were not linear over the whole time range, implying that more than one process affected the adsorption: the first one representing surface adsorption at the beginning of the reaction and the second one was the intraparticle diffusion at the end of the reaction. The results in this study indicated that orange peel was an attractive candidate for removing furadan from the aqueous solution.

Abstract: The study examined the adsorption behaviour of Direct Violet 51 (DV 51) dye from aqueous solution onto natural rubber chips. The effects of various operational parameters such as adsorbent dose, contact time, pH and dye concentration were investigated using the batch adsorption technique. The natural rubber sheet (thickness 2mm) was prepared by compression moulding and cut into 5 mm square pieces. The point of zero charge (pH_pzc) of the rubber chips was determined using the pH drift method. Equilibrium adsorption data were analysed by means of Langmuir and Freundlich isotherms, and adsorption data by spectrophotometer. It was found that the optimum adsorbent dose was 3g and optimum contact time was 120 minutes. The highest removal efficiency was found at pH 7. The explanation may be understood in terms of the pH_pzc of the rubber chip (pH_pzc=7.45), at which point the rubber surface is neutral. The surface charge of the rubber chip is therefore positive when the solution pH is below pH_pzc. Because of its basicity, Direct Violet therefore tends to be adsorbed onto the surface of natural rubber chips. In addition, at pH 7 common salt (NaCl) was also found, which is believed to reduce the repulsion between the rubber chips and the dye, allowing the dye to diffuse more easily on to the surface of the rubber chip fibres, thereby improving their dyeability. The adsorption data correlated well with the Langmuir isotherm model, suggesting the monolayer adsorption behaviour.

Abstract: Graphene-based composites show much better adsorption capacity and other properties than single graphene under the same operating conditions. This paper summarized the different kinds of graphene-based composites removing various heavy metals and organic pollutants in wastewater.

Abstract: This paper investigates the adsorption behavior of triblock copolymer Poly (propylene oxide)-poly (ethylene oxide)-poly (propylene oxide), PPO-PEO-PPO on silicon and iron surfaces by using the contact angle goniometer, spectroscopic ellipsometer and atomic force microscopy (AFM). After adsorption, the decrease of water contact angle was observed on each surface; and a larger reduction of water contact angle occurred on the surface covered by the copolymer film with longer and higher weight percent of hydrophilic PEO block. This means that the PEO block may be on the top of the adsorbed copolymer film. The film thickness measurement shows that the copolymer with longer and higher weight percent of PPO block forms a thicker film on the hydrophobic surface, which suggests that the hydrophobic PPO block of the copolymer in the aqueous solution plays the main role during the adsorption of PPO-PEO-PPO onto the hydrophobic surface. It has been found from the AFM results that the roughness of the surface decreased after adsorption and the smoother topography was observed on the surface adsorbed by a thicker adsorbed film.

Abstract: In recent years there is a continuously increasing worldwide concern for the growth of wastewater treatment technologies. The utilization of iron-oxide nanomaterials has attracted much interest due to their unique properties, such as extremely small size, high surface-area-to-volume ratio, surface modifiability, excellent magnetic properties and great biocompatibility. In this study, Fe3O4 coated polypyrrole (PPy) magnetic nanocomposite was prepared via in situ polymerization of pyrrole monomer for the removal of highly toxic Cr (VI).The PPy/Fe3O4 nanocomposite was characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction pattern (XRD) and Fourier-transformed infrared spectroscopy (FTIR). The adsorption properties of the PPy/ Fe3O4 nanocomposite for the removal of Cr (VI) were thoroughly studied. Up to 99% adsorption was found with 220 mg/L Cr (VI) aqueous solution at pH 2. Adsorption results showed that Cr (VI) removal efficiency by the nanocomposite decreased with an increase in pH. Adsorption kinetic was best described by the Pseudo-second-order rate model. Desorption experiment showed that in spite of the very poor recovery of the adsorbed Cr (VI); the regenerated adsorbent can be reused efficiently at least for two successive adsorptiondesorption-cycles without significant loss of its initial capacity.

Abstract: The preparation of mesoporous silica coated hydroxyapatite (HAp) ceramics is reported. The adsorption of proteins onto hydroxyapatite (HAp) is important in a variety of oral or osseous biological events. HAp has been used as bone filler, and the protein adsorption onto HAp materials is of importance for the bond formation. HAp has been also used as the material for column packing of liquid chromatography to separate and refine proteins due to the adsorptive capabilities with respect to the HAp. Mesoporous silica (MPS) materials have been extensively studied as carriers of bio-molecules due to their potential practical applications in medical materials. Pore diameters of 1.5 30 nm of the periodic mesoporous materials are close to the diameters of target molecules and enclosure of the protein in a well-defined space may help to prevent denaturation. Previously, we reported the MPS coating on the porous hydroxyapatite (HAp) ceramics obtained by dip-coating method. Protein adsorption on the porous HAp with the MPS coatings was evaluated using UV-VIS spectrometry, and the quantity of BSA adsorbed onto the HAp ceramics with the MPS coatings is around 1.5 times high compared to that on porous HAp ceramics. In this study, the vapor-phase synthesis of MPS film on HAP ceramics was carried out to improve the protein adsorptive property of HAp ceramics. The quantity of adsorbed protein onto the HAp ceramic disc with MPS coatings is around 5 times high compared to that on HAp ceramic disc.

Abstract: With respect to the problems existed in the description of the adsorption characteristics of super-low rank and super-high rank coals using the conventional Langmuir adsorption model, in this paper, We first introduces the De Bore adsorption model into the coal seam gas adsorption, and utilizes the results of the ab initio calculation of quantum chemistry result and the isothermal adsorption test statistical results, simplifies the De Bore model equation. The new adsorption model is more suitable for describing the gas adsorption characteristics of the whole coal ranks. This new model has the stronger function and wider suitable scope than the Langmuir adsorption model.

Abstract: Alginate-diatomite immobilized microspheres were prepared through immobilized biosorption of diatomite and Mucor sp. by sodium alginate, which were employed to adsorb acephate and Hg²⁺ in wastewater. Several major factors were investigated. Results showed that initial concentration of acephate and Hg²⁺ were both 300ug/l, percent of adding immobilized microspheres full of Mucor sp.was 6%(m:m), rotating speed 160~200r/min. Keywords: Adsorption; Acephate; Hg²⁺; Mucor sp.

Abstract: In allusion to Cr³⁺s toxic effect on activated sludge in SBR process system, by determination of the Cr³⁺ adsorption rate, mlvss under different initial SVIs and different chromium loads, the Cr³⁺s toxic effect on activated sludge and the Cr³⁺s influence on chromium adsorption of activated sludge were studied. The research shows that within tolerance range, the activated sludge of SBR system can adsorb 60% chromium ion within 10min reaction. Moreover, with the increase of chromium load, the final chromium remnant rate decreases; within tolerance range, the increase of chromium load contributes to the adsorption of chromium ion and the acceleration is subject to initial SVI. Within non-tolerance range, the ability of SBR process system to adsorb chromium decreases greatly; The whole curve of chromium remnant rate shifts upward with the increase of chromium load level. Within 10mins reaction, the adsorption rate of chromium is about 50% under best condition.