Current, Limiting Adsorption

Protein adsorption at oil-water interfaces interfacial structure and function of proteins in emulsions

The potency of PPD is very stable when kept as a lyophilized preparation or as a solution of high concentrations, but, as is well known, when diluted to the practical concentrations such as used in skin-testing for human, its potency diminishes rather rapidly. It has been considered that such decrease in potency is not due to denaturation of PPD, but due to its adsorption onto the surface of glass- or plastic-container. The adsorption of PPD had been studied by several authors with radiolabeled PPD or by the potency test in experimental animals or human. However, either method is not satisfactory because they are not quantitative and reproducible. Consequently, we developed a new method basing on ELISA to measure such low concentrations of PPD as used in skin-testing in human. Using this new method, we analyzed the adsorption of PPD onto glass-surface. The major characteristics of the PPD adsorption revealed by the present studies are as follows; (1) The adsorption of PPD takes place very rapidly immediately after the distribution of PPD solution to a new container and then proceeds in slower rates. (2). The rate of adsorption is influenced by both temperature and concentration of PPD solution. The rates of adsorption are almost the same at -80 degrees C and at 6 degrees C, much higher at 22 degrees C and further higher at 37 degrees C at any concentration tested. At -80 degrees C and 6 degrees C, there is no difference among the adsorption rates at three different concentrations, but at 22 degrees C and 37 degrees C, the rate of adsorption at the lowest concentration (0.25 microgram/ml) is much higher than those at higher concentrations. (3) The amounts of PPD adsorbed are determined by the surface area of glass in contact with PPD solution. (4) The larger the volume of PPD solution distributed, the bigger the absolute amount of PPD adsorbed, but the smaller the rate of adsorption. (5) So-called "volume effects" are evidenced. Commercially available Japanese PPD preparations have been produced and adjusted their potency taking such adsorption phenomena into consideration. But, if undue adsorption is induced by unappropriate handling and/or usage, the potency might be diminished. Especially, the single-dose preparation may be affected most strongly by so-called "volume-effects". Standard handling and usage recommended by the manufacturer are strictly required.

Every year there is deterioration in water quality. This is due to human activity. The current environmental strategies of many countries motivate the scientific community to develop reliable, economically viable and environmentally friendly technologies that are able to remove pollutants from the environment, including water. The study purpose is to determine of influence regularity of the bio-adsorbent composition and amount, which consists of red and black tea leaves mixture, on the Cd, Co and Ni adsorption process based on experimental data. As well as determine the most rational bio-adsorbent dose and the necessary red and black tea dose in bio-adsorbent to achieve MPC of heavy metals, with which process duration will be minimal. Initially, to study the adsorption process kinetics, the nature of the curve that describes the obtained experimental values was visually analyzed. To determine the adsorption process kinetic regularity, which most adequately and reliably describes the experimental data and to determine the values of the coefficients in the exponential regularity, the least squares method was used. It was observed that for Cd and Co, an increase in the black and red tea amount leads to a drastic reduction of the adsorption process time (up to 10 times); while for Ni the black tea addition slows down the adsorption process. Ni adsorption is the most complex and for certain bio-adsorbent composition values, complete Ni removal cannot be achieved in a technologically reasonable adsorption time. The technological process of Cd, Co and Ni adsorption can be expedient, if it is carried out in several stages with optimal red and black tea amounts for each of the metals. Adsorption process kinetic regularity, which was determined, can be used to calculate of adsorption process technological parameters in values wide range.

Arsenic (As) and antimony (Sb) are toxic elements. They pose an emerging environmental risk and threaten human health. However,the removal of As and Sb remains a contemporary challenge due to the lack of knowledge in their surface chemistry and efficient adsorbent. In this study,the adsorption reaction of As and Sb on high-index {201} TiO2 (HTiO2) was examined. The results show that the adsorption isotherms of As(Ⅲ),Sb(Ⅲ),As(Ⅴ),and Sb(Ⅴ) on HTiO2 conformed to the Langmuir model with a maximum adsorption capacity of 0.407,0.861,0.197,and 0.181 mmol·g-1,respectively. The kinetics of As and Sb adsorption on HTiO2 followed the pseudo-second order reaction,suggesting that chemical adsorption was the rate-controlling step. The adsorption pH envelope experiments demonstrated that pH had a negligible effect on As(Ⅲ) adsorption. Sb(Ⅲ) adsorption was enhanced with increasing pH and then decreased. The adsorption of As(Ⅴ) and Sb(Ⅴ) was favorable at acidic pH and decreased with the increase in pH. Zeta potential shows that the HTiO2 surface was negatively charged over the full pH range upon As and Sb adsorption,indicating the formation of negatively charged inner-sphere As and Sb complexes on HTiO2. This study provides new information for simultaneous As and Sb removal from contaminated water.

Characterization of the pristine barite mineral was established using a scanning electron microscope (SEM) and Fourier Transform Infra-Red (FTIR). Barite was applied for sodium oleate and sodium palmitate adsorption in aqueous solutions. Equilibrium adsorption data were fitted into two adsorption isotherms, three kinetic models and thermodynamic study. The concentration of the ion and pH in the solution proved to be a controlling factor in the adsorption process. Sodium oleate and sodium palmitate soaps adsorbed strongly onto the barite mineral at pH 9 and a temperature of 293k. They result was affected by the high bulk density and chemical resistance nature of barite indicated by successive increase in dosage amount. The effect of concentration and time typically gave a C-type adsorption isotherm. Adsorptive isotherm showed that sodium palmitate adsorption over natural barite was better described by the Langmuir adsorption isotherm while oleate desorption gave a good fitting with Freundlich isotherm. The adsorptive kinetics of sodium palmitate fitted well into pseudo 1 st order and 2nd order kinetics. Intra particle diffusion was not the rate-determining step. Thermodynamic study showed a physio-sorption that was exothermic. Hence the findings showed that pristine barite absorbs at optimum pH and temperature of 9 and 293K.

Laminate zeolite structure prepared using papermaking techniques for carbon dioxide capture: synthesis, characterisation and performance

The aim of this Ph.D. work is to investigate the adhesion and de-adhesion of organic coatings on galvanized steel substrate. Chapter 1 introduces the project aim and research outline. Chapter 2 investigates Zn oxide semiconductor properties as the major compound formed on galvanized steel. The results showed a clear effect of surface treatment on Zn oxide doping concentration and flatband potential. Moreover, an obvious relation between Zn oxide composition and flatband potential was detected. The deposition mechanism of Zr-based conversion coatings, as potential replacement of the existing conversion coatings, on differently pretreated Zn surfaces has been studied in chapter 3. It was found that Zr deposition rate and the composition of the obtained conversion layer strongly depend on the initial hydroxyl fraction and surface roughness. Studying the metal-polymer interfacial bonding is extremely difficult due to the relatively high polymer thickness masking the interface region. Consequently, the metal-polymer interfaces are modeled in chapters 4-7 by adsorption of the representative molecules. Chapter 4 compares the adsorption properties of carboxylic based molecules on Zn and Fe substrates. It was shown that the obtained interfacial configurations are different on Zn and Fe substrates. In this case, one end adsorption of succinic acid molecules was promoted on Fe, while adsorption of Zn was conducted mainly with both ends. Consequently, Zn was selected for continuation of the research to explore more details of the interfacial properties. Chapter 5 examines the effects of an external potential on adsorption properties of the carboxylic model compounds. The results showed that the applied potential slightly increases the amount of adsorbates, which may contribute to a better adhesion. Moreover, the applied potential increases one-end adsorption of succinic acid molecules due to a C-C bonding cleavage. Desorption of the formed carboxylates was examined by means of cyclic voltammetry in chapter 6. It was shown that the molecular type and surface pretreatment affect the desorption process and consequently the interfacial bonding strength. It was found the metal-polymer interaction is accompanied by an electron exchange in the interfacial region. Consequently, scanning Kevin probe (SKP) measurements were performed to evaluate the Volta potential changes due to the adsorption. The results showed that the amount of electron transfer is correlated to the interfacial bonding density and molecular chain length. Additionally, an effect of adsorption configuration was detected on the obtained Volta potential shift. In the next step, the interfacial bonding properties of the real carboxylic coatings and Zn substrate were evaluated in chapters 8-10. Chapter 8 assesses the interfacial bonding of the residue polymer layers obtained after a dedicated polymer removal procedure. A comparable interfacial bonding mechanism was detected for the real coatings and model compounds applied on Zn surfaces. Chapter 9 investigates in-situ the interfacial bonding formation upon application of the polymers on Zn surfaces in a Kretschmann geometry. An equivalent interfacial bonding mechanism was detected compared to those obtained through the adsorption of the model compounds and residue layers. Additionally, it was shown that the metal-polymer interaction takes place in a relatively short time, while polymerization proceeds afterwards. The interfacial bonding degradation was examined by means of an integrated ATR-FTIR and EIS set-up in a Kretschmann geometry and described in chapter 10. The results showed a beneficial role of the polymerization process in the formation of lateral bondings blocking water penetration through the polymer structure. Moreover, it was found that the duration of the disbonding process depended on the Zn surface hydroxyl fraction.

Pollution control is necessary with the advancement of modern manufacturing industry as various forms of industrial wastes are generated. Adsorption has been considered a safer and less expensive approach for the remediation of environmental damage caused by the release of heavy metal ions, toxic dye molecules or harmful gases. Ordered mesoporous carbon materials are ideal as adsorbents due to their characteristic features including a high surface area, an interlinked pore system with uniform and accessible pores, a tuneable pore wall framework with different functional groups, as well as physical and chemical stability. In particular, uniform ordered mesoporous spheres have great potential for practical applications in dynamic adsorption. The traditional nanocasting approach to synthesize monodisperse carbon spheres involves complex, time-consuming procedures which present difficulties in industrialising the process while the conventional aerosol approach results in polydisperse size distribution, irregular pore sizes and small particle sizes (sub- to a few micrometers). In recent times, the microfluidic jet spray drying technique has been introduced for the synthesis of uniform mesoporous carbon microspheres. However, the characteristics of this class of material and its potential applications have not been fully understood. The main aim of this research was to investigate the ordered mesoporous carbon spheres synthesized from this spray drying technique as promising adsorbents for environmental applications. First, the selective adsorption of the mesoporous spheres in binary dye mixtures was investigated based on the adsorption rate and equilibrium capacity in comparison with that of mesoporous thin film and activated carbon. The results showed that the spherical particles preferentially removed the smaller dye molecule from the mixture, and that the nano sieve layer on the surface of the sphere gave rise to this size exclusion feature. Secondly, the functionalisation of the mesoporous carbon spheres was investigated using a mild oxidant at different durations and temperatures as well as a strong oxidant at different concentrations. Based on the study of the pore evolution, mesostructural stability and surface functionalisation, it was found that the treated samples showed higher adsorption of aniline as compared to the pristine sample. In summary, the findings from these two studies demonstrate the favourable adsorption characteristics of the mesoporous carbon spheres obtained from the unique spray drying technology. In other words, the size exclusion effect on the surface of the sphere resulted in the favourable adsorption as did the tuneable carbon framework for improved interaction with guest molecules. While the adsorption experiments from both studies were conducted in batch condition, this study has broader implications in the application of continuous column adsorption. This research thus opens the possibility for the fast and scalable synthesis of a new class of carbon adsorbent for environmental application.

Vetiver grass has been widely used for soil erosion control and runoff protection. The present work provided an alternative application of vetiver grass as adsorbent materials for wastewater treatment. The adsorbent materials was synthesised in two different methods. The absorbent 1 was synthesized by heating the vetiver grass at 300C. In the meanwhile, the adsorbent 2 was synthesized by heating at 750C and adding some chemicals (such as TPABr and NaOH). The XRD patterns suggested that the adsorbent 1 could be activated carbon. On the other hands, the adsorbent 2 was unidentified materials. Both adsorbents were able to treat dye wastewater with >99% of effectively. This performance is greater than using a commercial activated carbon. However, at the highest wastewater concentration, the adsorbent 1 obtained the better efficiency rather than the adsorbent 2.

To investigate the adsorption property of H2 and CO2 on the organic ligand of C-MOF-5 (H2BDC) and T-MOF-5 (ZnO-doped H2BDC (ZnO-H2BDC)), Density functional theory (DFT) method was performed. First, the adsorption of ZnO on H2BDC resulted in examining binding energies, the charge transfer, density of states, dipole moments and adsorption geometries were investigated. The binding properties have been calculated and investigated theoretically for ZnO-doped H2BDC in terms of binding energies, band structures, Mulliken charges, and density of states (DOSs). According to obtained results, the H2BDC was strongly doped with ZnO. H2 and CO2 adsorption capacities for ZnO-doped H2BDC are significantly enhanced while there are low adsorption capacities for H2BDC. According to results, at least in the organic ligand of the MOF-5, the highest and lowest adsorption of CO2 (or H2) is attributed to the T-MOF-5 and C-MOF-5 respectively. Our calculations reveal that ZnO-doped H2BDC system (T-MOF-5) has much higher adsorption energy and higher net charge transfer value than pristine H2BDC (C-MOF-5). Also by changing in structure from cubic to tetragonal, the main site for H2 and CO2 adsorption was changed.

The inhibitive effect of hexadecyltrimethylammonium bromide (HDTAB) on the corrosion of aluminium alloy (AA3003) in 1 M hydrochloric acid medium was studied by weight loss method in relation to the temperature (25 to 55°C) and inhibitor concentration range 5.10-4 to 10-2 M. This study showed that the inhibitor adsorbs on aluminium alloy (AA 3003) according to the modified Langmuir adsorption isotherm; the inhibitor efficiency decreases with increasing temperature. Adsorption free energies (ΔG°ads) and apparent activation energies (Ea) were determined. The Adsorption free energies reveal that the adsorption process is spontaneous. Furthermore, some adsorption thermodynamic parameters (ΔH°ads, ΔS°ads, Qads) were estimated. Phenomenon of physical adsorption was proposed from the thermodynamic functions of adsorption and activation parameters obtained. Key words: Corrosion, inhibitor, adsorption, desorption, free adsorption energy, activation energy.

In this study involves removing of Brilliant Dyes, were which (Brilliant Green {BG} and Brilliant Cresyl Blue {BCB}) by using Iraqi Siliceous Rocks Powder (SRP). Adsorption isotherms were studied and the factors which prefer it, like temperature and salt effect, Adsorption isotherms of dyes, Brilliant Cresyl Blue {BCB} was found to be comparable to Langmuir equation according to Giles classification, isotherms dye Brilliant Green {BG} was found to be comparable to Freundlich equation more than dye Brilliant Blue {BCB} according to Giles classification. The adsorption process on this surface (SRP) studied at different temperatures, the results showed that the adsorption of dyes (BCB, BG) on the surface increased with increased temperature (Endothermic process). According to valuable to the above results of the thermodynamic functions (ΔG, ΔS, ΔH) were calculated. The salt effect on the adsorption of dyes at (20C°) it was found that the adsorption increased by the presence of salt. The kinetics of the adsorption was studied, the results were treated according to (Lagergren equation) and treated according to the second-order equation model. The kinetics experimental data showed that the adsorption was pseudo order and changes according to the changing conditions.

Vapor adsorption of water, benzene, hexane, and cyclohexane on three natural solids (a bentonite and two soils) that covered a wide range of soil organic matter (SOM) content were measured to examine the effects of SOM on the adsorption of water and volatile organic compounds (VOCs). The surface area and pore structure of the examined solids were first characterized based on the classical and fractal analyses of the nitrogen adsorption isotherms. The adsorption isotherms of water and VOCs vapor at room temperature were then determined. It was found that the average pore diameter and pore connectivity (surface area, total pore volume, and surface roughness) of solid is proportional (inversely proportional) to the fraction of organic matter in the solids. On the other hand, the high adsorption capacity of polar liquids (water) on bentonite and peat is consistent with the polar nature of the soil mineral and organic matter. Moreover, for benzene (hexane and cyclohexane) adsorption, peat (bentonite) possessed the highest adsorption capacity among the examined solids. The effects of both surface area and pore structure on the organic vapor adsorption characteristics of natural solids are discussed.

This study aims to determine the optimum mass, optimum agitation times and the effect of the concentration of direct red dye was adsorbed by charcoal of ambon and kepok banana peels. And to determine the influence of activator concentration of NaOH on the adsorption capacity of ambon and kepok banana peels on the adsorption of direct red dye. The subject of this study is the ambon and kepok banana peels. The object of this study is the efficiency of adsorption. The parameters in this study are the mass of adsorbent, agitation times, dye concentrations, and the concentration of NaOH activator. Adsorption capacity of banana peels to direct red dye is determined by the difference of concentration before and after adsorption. The concentration of dye was determined using a spectrophotometer at an optimum wavelength of visible light. The result shows that the optimum mass and agitation time for direct red dye adsorption which are adsorbed by the charcoal both of ambon and kepok banana peels adsorbent is 0.5 grams per 50 mL of the adsorbate and 2 hours, respectively. Direct red dye concentration does not affect the efficiency of adsorption ambon banana peel charcoal but influences the efficiency of adsorption kepok banana peel charcoal. The greatest adsorption ability of ambon and kepok banana peels are given by NaOH activator at 0.5 M and 1 M. Key words: banana peel, banana peel charcoal, direct red, agitation time

Rice husks chemically modified with three different treatment methods; sodium hydroxide, nitric acid, and distilled water, were investigated to compare their color removal efficiencies for two dyes; Basic Red 4G (a cationic dye) and Direct Supra Red BWS (an anionic dye). The results revealed that the basic dye was adsorbed by these adsorbents better than the direct dye. The modified rice husk prepared using sodium hydroxide treatment showed the highest color removal efficiency (97% for Basic Red 4G) among the three modified rice husks. This modified rice husk was selected for further study of the adsorption equilibrium and adsorption isotherm. The results of adsorption equilibrium investigation fitted well with Langmuir model indicating that the dye adsorption takes place as a monolayer adsorption, based on the assumptions of the Langmuir model. The maximum adsorption capacity calculated from the Langmuir model was calculated to be 6.2 mg/g and 2.6 mg/g for Basic Red 4G and Direct Supra Red BWS, respectively. While the 1/ n values from Freundlich model were calculated as 0.2702 and 0.5841 for Basic Red 4G and Direct Supra Red BWS, respectively, indicating favorable dye adsorption. This modified rice husk is a potential alternative adsorbent for color removal in the wastewater from dyeing process using cationic dyes.