Kinetics and thermodynamic for sorption of arsenate by lanthanum-exchanged zeolite

Zeolites are crystalline, hydrated aluminosilicate containing exchangeable alkaline and alkaline earth cations in their structural frameworks. Since zeolites have permanent negative charges on their surfaces, they have no affinity for anions. However recent studies have shown that modification of zeolites with certain surfactants or metal cations yield sorbents with a strong affinity for many anions. In this paper, modification of zeolites (zeolite A, X and ZSM5) were performed by exchange of naturally occurring cations with lanthanum ion that forms low solubility arsenate salt. The exchanged zeolites were used to sorb arsenate from aqueous solution. Among parameters investigated were effect of pH, arsenate initial concentrations, contact time and temperature. The maximum exchanged capacity of La(III) ion was obtained when using solution with initial pH of 4. Zeolite X gives the highest La(III) exchanged capacity compared to other zeolites. The results showed that As(V) sorption by La-zeolites occurred at about pH 6.5 and increased as pH increased and reaching maximum at equilibrium pH about 7.8. On the other hand, almost no arsenate sorption occurred on unexchanged zeolites. This indicates that La(III) ion on the exchanged zeolites is taking part on the As(V) sorption via surface precipitation. The results also showed that the sorption capacities increased with increasing initial As(V) concentrations. The sorption followed Langmuir model with maximum sorption capacities of 0.41, 0.21 and 0.19 mmol/g at 25°C for La exchanged zeolite X (La-ZX), La exchanged zeolite ZSM5 (La -ZSM) and La exchanged zeolite A (La-ZA), respectively. The amo unts of sorption of As(V) by La exchanged zeolite increased as temperature increased from 25 to 70°C indicating that the process is endothermic. The free energy changes (DG°) for the sorption at 25°C were -10.25, -9.65 and -8.49 kJ/mol for La-ZX, La -ZSM and La-ZA, respectively. The negative values of DG° meant that the sorption of As(V) ions on La-exchanged zeolite was spontaneous, perhaps because the La(III) had high affinity towards the arsenic ion as indicated by a low Ksp value of of lanthanum arsenate. A slightly positive entropy change for sorption of As(V) ion on La-exchanged zeolite could be due to fixation of the ions on the La(III) exchange sites that was randomly distributed on the sorbents. The kinetics study showed that the As(V) sorption followed first order kinetic model. The first-order kinetic constants for the sorption are 2.77x10-3, 2.25x10-3 and 1.60x10-3 min-1 for La-ZX, La -ZSM and La-ZA, respectively

Morphological Studies Of Dhsa/Dhsa-Octyl Ester/Rbd Palm Kernel Olein/Medium Chain Triglycerides System

Dihydroxystearic acid (DHSA) and octyl dihydroxystearate (DHSA-octyl ester) have been previously prepared from palm oleic acid and preliminary results showed that these compounds are suitable in personal care and cosmetics products. The objective of this research is to study the phase behavior in ternary system of DHSA/DHSA-octyl ester/RBD Palm Kernel Olein (RBDPKOo) & MCT at 85oC. From the ternary phase diagram, results showed that all ratios of were completely in two-phase region with various concentrations of RBDPKOo and MCT. The phase changes were observed through polarizing light while the formation of texture was confirmed using polarizing microscope combination with heating. Needles and spherulite textures were found in this system

Preparation and characterization of conducting polymer composite films: polypyrrole and polyethylene glycol

Polypyrrole-poly ethylene glycol (Ppy -PEG) composites were synthesized by electrochemical method using p-toluene sulfonate as a dopant in aqueous medium. Polyethylene glycol was used as the insulating material in order to impart enhanced mechanical properties to the conducting polymer composite films. The composite films were synthesized with various percentages of PEG, and were characterized by FT-IR spectroscopy, conductivity measurement, optical microscopy (OP), X-ray diffraction (XRD) and dynamic mechanical analysis (DMA). The FT-IR result reveals the successful incorporation of PEG into the polypyrrole structure forming Ppy-PEG composite films. The conductivity of the composite films prepared from using 0.20% PEG was found to exhibit the highest conductivity (61.28 Scm-1) among all the prepared composite films measured at room temperature. The optical microscopy of Ppy -PEG shows the globular surface morphology. The XRD analysis of Ppy -PEG composite films shows that the composite films are amorphous. The enhanced mechanical properties of the Ppy -PEG composite films are the direct consequence of incorporating PEG in the polypyrrole structure

Synthesis and characterization of molecularly imprinted polymer membrane for the removal of 2,4-dinitrophenol.

Molecularly imprinted polymers (MIPs) were prepared by bulk polymerization in acetonitrile using 2,4-dinitrophenol, acrylamide, ethylene glycol dimethacrylate, and benzoyl peroxide, as the template, functional monomer, cross-linker, and initiator, respectively. The MIP membrane was prepared by hybridization of MIP particles with cellulose acetate (CA) and polystyrene (PS) after being ground and sieved. The prepared MIP membrane was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The parameters studied for the removal of 2,4-dinitrophenol included the effect of pH, sorption kinetics, and the selectivity of the MIP membrane. Maximum sorption of 2,4-nitrophenol by the fabricated CA membrane with MIP (CA-MIP) and the PS membrane with MIP (PS-MIP) was observed at pH 7.0 and pH 5.0, respectively. The sorption of 2,4-dinitrophenol by CA-MIP and PS-MIP followed a pseudo-second-order kinetic model. For a selectivity study, 2,4-dichlorophenol, 3-chlorophenol, and phenol were selected as potential interferences. The sorption capability of CA-MIP and PS-MIP towards 2,4-dinitrophenol was observed to be higher than that of 2,4-dichlorophenol, 3-chlorophenol, or phenol

Sorption removal of arsenic by cerium-exchanged zeolite P

Modification of zeolite P was performed by exchanged of its sodium with cerium(III). The resulting cerium-exchanged zeolite P, (CeZP) did not change in its crystallinity compared to original zeolite. The CeZP was subsequently used to sorb As(V) from aqueous solution. Maximum sorption of As(V) by CeZP occurred at pH range 3–10. In addition, the sorption capacity increased with increasing initial As(V) concentrations. The sorption follows Langmuir model with maximum sorption capacity of 8.72 mg g−1 at 25°C and increased to 23.42 mg g−1 at 90°C, indicating an endothermic process. The arsenic sorption by CeZP was not affected by the present of nitrate, chloride, sulphate, carbonate and bromide but was reduced significantly in the presence of phosphate. This study shows that the as prepared CeZP was found effective for the removal of arsenic from wastewater sample of wood treatment industry

Preparation and characterization of poly(ethyl hydrazide) grafted oil palm empty fruit bunch for removal of ni(ii) ion in aqueous environment

Poly(ethyl hydrazide) grafted oil palm empty fruit bunch (peh-g-opefb) fiber has been successfully prepared by heating poly(methylacrylate)-g-opefb at 60 °C for 4 h in a solution of hydrazine hydrate in ethanol. The chelating ability of peh-g-opefb was evaluated based on removal of Ni(II) ions in aqueous solution. Adsorption of Ni(II) by peh-g-opefb was characterized based on effect of pH, isotherm, kinetic and thermodynamic study. This cheap sorbent based on oil palm empty fruit bunch fiber has a great future potential in water treatment industries based on high adsorption capacity, biodegradability and renewability

Influence of bath temperature and PH value on properties of chemically deposited CU4SNS4 thin films.

Thin films of Cu4SnS4 semiconductors were prepared by chemical bath deposition technique in aqueous solutions. The effects of various bath temperatures (40, 50 and 60 °C) and pH values (pH 0.5, pH 1.0 and pH 1.5) on growth of films were reported. The structure and morphology characteristics of thin films of Cu4SnS4 grown on indium tin oxide glass substrates were investigated by X-ray diffraction and atomic force microscopy techniques. The optical properties were measured to determine the transition type and band gap value. The thin films produced were found to be polycrystalline with orthorhombic structure. The X-ray diffraction data showed that the most intense peak at 20 = 30.2° which belongs to (221) plate of Cu4SnS4. The films deposited at 50 °C were found to have the best photoresponse activity and smaller crystal size. At pH 1.5, the film showed well-covered entire substrate surface and the highest absorption values in AFM and optical study, respectively. The best condition to prepare good quality thin films can be carried out at 50 °C with pH 1.5. The bandgap value was found to be 1.4 eV with direct transition

Application of methyl fatty hydroxamic acids based on Jatropha curcas seed oil and their metal complexes as anti microbial agents

Hydroxamic acids, fatty hydroxamic acids and their metal complexes are known as compounds that have biological activity. They have been investigated as antimicrobial compounds and were applied as antibacterial and antifungal agents in pharmacy andpharmaceutical compounds. In this research, the methyl fatty hydroxamic acids (MFHAs) based on Jatrophacurcas seed oil and their metal complexes include the copper (II) methyl fatty hydroxamate (Cu-MFHs) and iron (III) methyl fatty hydroxamate (Fe-MFHs) were prepared and applied as anti microbial agents against the Escherichia coli (E. coli), Proteus vulgaris (P. vulgaris) andProteus mirabilis (P. mirabilis) as gramnegative bacteria; methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (S. epidermidis) as gram-positive bacteria ; Candida parapsilosis (C. parapsilosis) and Candida Albicans(C. Albicans) as yeast family of fungi. The results showed that the antimicrobial activity of MFHAs, Cu-MFHs and Fe-MFHs increase while their amounts increase. Also metal complexation of MFHAs caused the anti microbial activity arise and this activity is higher for complexation by Cu(II) compared to that of Fe(III). Comparing antimicrobial activity of MFHAs, Cu-MFHs andFe-MFHs based on Jatrophacurcas seed oil with several antibiotic drugs such as ampicillin, chloramphenicol, gentamicin streptomycin, tetracycline and nystatin against the mentioned microbial showed that the Cu-MFHs andFe-MFHs have very strong antimicrobial activity

Well diffusion method for evaluation of antibacterial activity of copper phenyl fatty hydroxamate synthesized from canola and palm kernel oils.

Hydroxamic acids and their derivatives have low toxicities and show wide range of biological activities. Copper complexes of phenyl fatty hydroxamic acids (Cu-PFHs) were prepared in a biphasic organic / aqueous medium from phenyl fatty hydroxamic acids (PFHAs) and copper nitrate. The products were separated by decantation of organic phase from aqueous phase followed by evaporation of the solvent. Elemental analysis, UV-Vis spectra and FTIR spectra showed that Cu-PFHs were formed in the solution from the complexation of PFHAs and copper ion. The antibacterial activity of PFHAs and Cu-PFHs from canola and palm kernel oils were investigated against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) using well diffusion method. The results showed that Cu-PFHs have higher antibacterial activity compared to PFHAs. Antibacterial activity of Cu-PHAs from canola oil against E.coli was significantly higher than hloramphenicol and cefotaxime

Chemical bath deposition of NiSe thin films from aqueous solutions.

The nickel selenide thin films were prepared onto microscope glass slides by a chemical bath deposition technique. The X-ray diffraction, scanning electron microscopy, and atomic force microscopy were used for their structural and morphological characterization. The X-ray diffraction results showed that the thin films prepared for longer deposition time and higher pH were polycrystalline with rhombohedral structure. The atomic force microscopy and scanning electron microscopy results indicated that the thin films covered the glass substrate completely and consisted of irregularly shaped grains. The optical properties of thin films were determined from analysis of the measured absorbance spectrum. The nickel selenide thin films exhibited direct band-gap transition with band gap energy of 1.8 eV