Sutha Khaodhiar

Effects of Surface Functional Groups and Porous Structures on Adsorption and Recovery of Perfluorinated Compounds by Inorganic Porous Silicas

The effects of porous structures and surface functional groups (silanol, 3-aminopropyltriethoxy, 3-mercaptopropyltrimethoxy, n-octyldichloroethoxy, and titanium substitution) on perfluorinated compounds (PFCs) adsorption and recovery were evaluated. The adsorption of PFCs on all adsorbents followed the pseudo-second-order model, and the adsorption rate was controlled by the pore diffusion, except for microporous zeolites and powder activated carbon (PAC). 3-aminopropyltriethoxy-grafted surface produced the highest PFCs adsorption capacities. Perfluorooctane sulfonic acid (PFOS) recovery from silica-based adsorbents (by ethanol extraction) efficiencies were higher than those of PAC and approached 100%. Hydrophobic organic functional groups can protect mesoporous structure from hydrolysis reactions in adsorption and solvent recovery processes. Supplemental materials are available for this article. Go to the publishers online edition of Separation Science & Technology to view the free supplemental file.

Adsorption characteristics of haloacetonitriles on functionalized silica-based porous materials in aqueous solution.

The effect of the surface functional group on the removal and mechanism of dichloroacetonitrile (DCAN) adsorption over silica-based porous materials was evaluated in comparison with powdered activated carbon (PAC). Hexagonal mesoporous silicate (HMS) was synthesized and functionalized by three different types of organosilanes (3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and n-octyldimethysilane). Adsorption kinetics and isotherm models were used to determine the adsorption mechanism. The selective adsorption of five haloacetonitriles (HANs) in the single and mixed solute systems was also studied. The experiments revealed that the surface functional groups of the adsorbents largely affected the DCAN adsorption capacities. 3-Mercaptopropyl-grafted HMS had a high DCAN adsorption capacity compared to PAC. The adsorption mechanism is believed to occur via an ion-dipole electrostatic interaction in which water interference is inevitable at low concentrations of DCAN. In addition, the adsorption of DCAN strongly depended on the pH of the solution as this related to the charge density of the adsorbents. The selective adsorption of the five HANs over PAC was not observed, while the molecular structure of different HANs obviously influenced the adsorption capacity and selectivity over 3-mercaptopropyl-grafted HMS.

Effect of sulfate on the methanogenic activity of a bacterial culture from a brewery wastewater during glucose degradation.

The maximum specific methanogenic activity (SMA) of a sludge originating from a brewery wastewater treatment plant on the degradation of glucose was investigated at various levels of sulfate on a specific loading basis. Batch experiments were conducted in serum bottles at pH 7 and 35 degrees C. A comparison of the values indicates that the SMA of this mixed culture was increased and reached its highest level of 0.128 g CH4 gas COD/(g VSS x d) when biomass was in contact with sulfate at a ratio of 1:0.114 by weight.

Effects of crystalline structures and surface functional groups on the adsorption of haloacetic acids by inorganic materials.

The effects of the crystalline structure and surface functional groups of porous inorganic materials on the adsorption of dichloroacetic acid (DCAA) were evaluated by using hexagonal mesoporous silicates (HMS), two surface functional group (3-aminopropyltriethoxy- and 3-mercaptopropyl-) modified HMSs, faujasite Y zeolite and activated alumina as adsorbents, and compared with powdered activated carbon (PAC). Selective adsorption of HAA(5) group was studied by comparing single and multiple-solute solution, including effect of common electrolytes in tap water. Adsorption capacities were significantly affected by the crystalline structure. Hydrogen bonding is suggested to be the most important attractive force. Decreasing the pH lower than the pH(zpc) increased the DCAA adsorption capacities of these adsorbents due to electrostatic interaction and hydrogen bonding caused by protonation of the hydronium ion. Adsorption capacities of HAA(5) on HMS did not relate to molecular structure of HAA(5). Common electrolytes did not affect the adsorption capacities and selectivity of HMS for HAA5, while they affected those of PAC.

Removal of haloacetonitriles in aqueous solution through adsolubilization process by polymerizable surfactant-modified mesoporous silica

To investigate the adsorption properties and mechanisms of haloacetonitriles (HANs), large-pore SBA-15 mesoporous silica (SBA-CHX) was synthesized using cyclohexane as a swelling agent, and the surface was modified with polymerizable gemini surfactant (PG). The structure and textural properties of the synthesized adsorbents were characterized. PG surfactant coverage on the surface and the degree of polymerization were confirmed with FT-IR analysis. Adsorption experiments were performed under batch conditions to evaluate the influence of the contact time, adsorption isotherms, the effect of the pH solution, and the selective adsorption of five haloacetonitriles (HAN(5)) in individual-solute and mixed-solute solutions and surfactant leaching studies. The results indicated that the hydrophobic HANs were efficiently adsorbed onto PG surfactant-modified SBA-CHX. The selective adsorption mechanisms involved a more complex interplay between the organic partition, surface adsorption (i.e., ion-dipole electrostatic interactions) and hydrophobic interaction that depended upon the adsorbent and adsorbate characteristics. An increased degree of halogen substitution in the HAN molecule significantly affected the adsorption capacity and selectivity by the organic partition. Polymerization of the polymerizable surfactant increased the stability of the adsorbed surfactant on the adsorbent surface.

Comparative study of heavy metal and pathogenic bacterial contamination in sludge and manure in biogas and non-biogas swine farms

The objective of this study is to determine and compare the heavy metal (Zn, Cu, Cd, Pb) and bacterial (E. coli, coliform and Salmonella spp.) contamination between swine farms utilizing biogas and non-biogas systems in the central part of Thailand. Results showed that average levels of E. coli, coliform, BOD, COD, Zn, Cu and Pb in sludge from the post-biogas pond were higher than the standard limits. Moreover, the levels of E. coli, coliform, Cd and Pb were also higher than the standard limits for dry manure. The levels of E. coli, coliform and BOD on biogas farms were lower than on non-biogas farms. Following isolation of Salmonella spp., it was found that Salmonella serovars Rissen was the most abundant at 18.46% (12/65), followed by Anatum 12.31% (8/65), and Kedougou 9.23% (6/65). The pathogenic strains of Salmonella serovars Paratyphi B var. java and Typhimurium were present in equal amounts at 4.62% (3/65) in samples from all swine farms. This study revealed that significant reduction in E. coli and coliform levels in sludge from covered lagoon biogas systems on swine farms. The presence of Salmonella as well as Cd and Pb, in significant amount in dry manure, suggests that there is a high probability of environmental contamination if it is used for agricultural purposes. Thus, careful waste and manure disposal from swine farms and the regular monitoring of wastewater is strongly recommended to ensure the safety of humans, other animals and the environment.

Adsorption and adsolubilization of polymerizable surfactants on aluminum oxide.

Surfactant-based adsorption processes have been widely investigated for environmental applications. A major problem facing surfactant-modified adsorbents is surfactant loss from the adsorbent due to loss of monomers from solution and subsequent surfactant desorption. For this study, a bilayer of anionic polymerizable surfactant (Hitenol BC 05, Hitenol BC 10 and Hitenol BC 20) and non-polymerizable surfactant (Hitenol N 08) was adsorbed onto alumina. The results of adsorption studies showed that as the number of ethylene oxide (EO) groups of the surfactants increased, the area per molecule increased and the maximum adsorption decreased. The lowest maximum adsorption onto alumina was for Hitenol BC 20 (20 EO groups) corresponding to 0.08 mmol/g or 0.34 molecule/nm(2) while the highest level of adsorption was 0.30 mmol/g or 1.28 molecule/nm(2) for Hitenol BC 05 (5 EO groups). This variation in adsorption was attributed to the increased bulkiness of the head group with increasing number of EO groups. Relative to the adsolubilization capacity of organic solutes, ethylcyclohexane adsolubilizes more than styrene. Styrene and ethylcyclohexane adsolubilization were both independent of the number of EO groups of the surfactant. For surfactant desorption studies, the polymerization of polymerizable surfactants increased the stability of surfactants adsorbed onto the alumina surface and reduced surfactant desorption from the alumina surface. These results provide useful information on surfactant-based surface modification to enhance contaminant remediation and industrial applications.

Phase behaviors, fuel properties, and combustion characteristics of alcohol-vegetable oil-diesel microemulsion fuels

ABSTRACT Biofuels are being considered as alternatives to fossil-based fuels due to depletion of petroleum-based reserves and pollutant emission concerns. Vegetable oils and bioalcohols have proven to be viable alternative fuels both with and without engine modification. However, high viscosity and low energy content are long-term operational problems with vegetable oils and bioalcohols, respectively. Therefore, vegetable oil-based microemulsification is being evaluated as a method to reduce the high viscosity of vegetable oils and enhance the miscibility of alcohol and oil phases. Studies have shown that microemulsification with different alcohols lead to varying fuel properties depending on their structure. The overall goal of this study was to formulate microemulsion fuels with single and mixed alcohol systems by determining the effects of water content, alcohol branching structure and carbon chain length on phase behaviors, fuel properties, and emission characteristics. It was found that microemulsion fuels using certain alcohols displayed favorable stability, properties, and emission characteristics. Flames of fuels with linear short-chain-length alcohols had larger near-burner blue regions and lower CO and soot emissions indicating the occurrence of more complete combustion. In addition to alcohol effects, the effect of vegetable oils, surfactants, and additives on emission characteristics were insightful in pursuit of appropriate microemulsion fuels as cleaner burning alternatives to both No.2 diesel and canola biodiesel.

Study of Hydrophobic VOCs Absorption Mechanism in a Bubble Column: Bubble Hydrodynamic Parameters and Mass Transfer Coefficients

The absorption mechanism of hydrophobic Volatile Organic Compounds (benzene) was investigated in a small bubble column. Effects of gas spargers (orifice size), gas flow rates, and absorbents (tap water, aqueous solution with non-ionic surfactant, and lubricant oily-emulsion) were analyzed in terms of absorption efficiency, bubble hydrodynamic, and mass transfer parameters. The results showed that the presence of non-ionic surfactant and lubricant oil affected the bubble hydrodynamic phenomena and the interfacial area (a) and the mass transfer parameters (volumetric mass transfer coefficient, kLa, and liquid-side mass transfer coefficient, kL). Absorption efficiencies of aqueous solutions with the previous substances as absorbents were significantly greater than those of tap water. These experimental results relate to the augmentation of benzene solubility in the liquid phase (absorbents) due to the presence of oily-particles and surfactant molecules. Moreover, high gas flow rates can decrease the VOCs absorption efficiency due to desorption mechanisms, associated with the mixing power in the liquid phase. Finally, it has been suggested that gas spargers with an orifice size smaller than 0.65 mm, 1 cm/s gas superficial velocity, and 50 mg/l lubricant oily-emulsion or 5 CMC non-ionic surfactant aqueous solutions are of optimal design and operation for hydrophobic VOCs absorption in the bubble column used in this study.

Rock Wool and Printed Circuit Boards (PCBs) as Partial Fine Aggregate Replacements in Cement Mortar

The utilization of industrial wastes such as, fly ash, silica fumes, and slag in construction materials, has been receiving increased attention due to its environmental friendliness and reduction of natural resources consumptions. This study investigates and compares the utilization of spent rock wool from industrial insulation and printed circuit boards (PCBs) (the non-metallic part) as a partial replacement for conventional fine aggregates in cement mortar. Each of the waste materials was used as a partial fine aggregate ranging from 0% to 20%, by weight. The cement mortar samples were cured at 7 days, 14 days and 28 days. To investigate the properties of the cement mortars with different amounts of industrial wastes, the density, compressive strength, transverse strength and thermal conductivity of each mortar variation were measured. The results indicate that the compressive and transverse strengths of the cement mortars decreased as more industrial wastes was present in the mixtures. However, the fine aggregate substitutes improved thermal resistance, as indicated by the decreasing thermal conductivity values of the cement mortars. Thus, the use of these two industrial wastes in cement mortar could be a viable option for non-structural and non-load bearing construction applications because these substitutes have the ability to produce mortar with suitable mechanical and insulating properties.