Degradation of Caffeine by Heterogeneous Photocatalysis Using ZnO with Fe and Ag

Abstract The organic compound caffeine when detected in environmental matrices such as surface waters and groundwater is considered as an emerging contaminant, in which its effects are still unknown. Therefore, in the present research, zinc oxide-based catalysts impregnated with iron and silver were prepared for the reaction of caffeine degradation by heterogeneous photocatalysis. The wet impregnation method with excess solvent was applied to the preparation of the materials, later they were characterized by adsorption of N2, X-ray diffraction and photoacoustic spectroscopy. Then, the photodegradation, photolysis and adsorption tests were carried out, in which it was observed that only the presence of the radiation or photocatalysts could not sufficiently degrade the caffeine, however when combined radiation with all the catalysts studied here presented degradation above 70% at the end of 300 minutes of the reaction, and the best catalyst studied was that containing 8% Ag in non-calcined ZnO. Thus, these results point out that the methodology employed in this research, both for the preparation of the catalysts and in the process of the photocatalysis reaction, was efficient in the degradation of the emerging contaminant, caffeine, which could later be used for a mixture of other contaminants.

Environmental drivers on leaf phenology of ironstone outcrops species under seasonal climate

ABSTRACT Banded iron formations (BIF) have a particular vegetation type and provide a good model system for testing theories related to leaf phenology, due to unique stressful environmental conditions. As a consequence of the stressful conditions of BIF environment, we hypothesize that most species would retain at least some significant canopy cover, even at the end of the dry season, independently of growth form - trees, shrubs, and sub-shrubs. Considering the strong seasonality, we also hypothesize that photoperiod and rainfall act as triggers for leaf fall and leaf flushing in these environments. The majority of the fifteen studied species had a semi-deciduous behavior and shed their leaves mainly during the dry season, with a recovery at the end of this season. In general, leaf flushing increased around the spring equinox (end of the dry season and start of the rainy season). A trade-off between leaf loss and leaf maintenance is expected in a community in which most plants are naturally selected to be semi-deciduous. Our results suggest photoperiod as a dominant factor in predicting leaf phenology.

Recent advances in the imaging of hepatocellular carcinoma

The role of imaging is crucial for the surveillance, diagnosis, staging and treatment monitoring of hepatocellular carcinoma (HCC). Over the past few years, considerable technical advances were made in imaging of HCCs. New imaging technology, however, has introduced new challenges in our clinical practice. In this article, the current status of clinical imaging techniques for HCC is addressed. The diagnostic performance of imaging techniques in the context of recent clinical guidelines is also presented.

Género y trayectorias profesionales de las médicas de familia en Andalucía, España, a comienzos del siglo XXI / Gender and career paths of female primary care physicians in Andalusia, Spain, at the beginning of 21st century

El objetivo de este trabajo es estudiar, desde una perspectiva feminista, la diversidad y homogeneidad en las trayectorias profesionales de las médicas de familia que ejercían en Andalucía a comienzos del siglo XXI, a través del análisis de los significados que ellas mismas confieren a su desarrollo profesional y de la influencia de los factores personales, familiares y laborales. Realizamos un estudio cualitativo con seis grupos de discusión. Participaron 32 médicas de familia que se encontraban trabajando en los centros de salud urbanos de la red sanitaria pública de Andalucía. El análisis del discurso revela que la mayoría de las médicas no planifican sus metas profesionales y que, cuando lo hacen, las van entrelazando con las necesidades familiares. Esto se traduce en que sus trayectorias profesionales sean discontinuas. Por el contrario, las trayectorias orientadas al desarrollo profesional y a la planificación consciente de metas son más frecuentes entre las médicas que ocupan cargos de dirección en centros de salud.

The purpose of this article was to study, from a feminist perspective, the diversity and homogeneity in the career paths of female primary care physicians from Andalusia, Spain in the early 21st century, by analyzing the meanings they give to their careers and the influence of personal, family and professional factors. We conducted a qualitative study with six discussion groups. Thirty-two female primary care physicians working in urban health centers of the public health system of Andalusia participated in the study. The discourse analysis revealed that most of the female physicians did not plan for professional goals and, when they did plan for them, the goals were intertwined with family needs. Consequently, their career paths were discontinuous. In contrast, career paths oriented towards professional development and the conscious planning of goals were more common among the female doctors acting as directors of health care centers.

Corrosion behavior of self-ligating and conventional metal brackets

Objective: To test the null hypothesis that the aging process in self-ligating brackets is not higher than in conventional brackets. Methods: Twenty-five conventional (GN-3M/Unitek; GE-GAC; VE-Aditek) and 25 self-ligating (SCs-3M/Unitek; INs-GAC; ECs-Aditek) metal brackets from three manufacturers (n = 150) were submitted to aging process in 0.9% NaCl solution at a constant temperature of 37 ± 1ºC for 21 days. The content of nickel, chromium and iron ions in the solution collected at intervals of 7, 14 and 21 days was quantified by atomic absorption spectrophotometry. After the aging process, the brackets were analyzed by scanning electron microscopy (SEM) under 22X and 1,000X magnifications. Results: Comparison of metal release in self-ligating and conventional brackets from the same manufacturer proved that the SCs group released more nickel (p < 0.05) than the GN group after 7 and 14 days, but less chromium (p < 0.05) after 14 days and less iron (p < 0.05) at the three experimental time intervals. The INs group released less iron (p < 0.05) than the GE group after 7 days and less nickel, chromium and iron (p < 0.05) after 14 and 21 days. The ECs group released more nickel, chromium and iron (p < 0.05) than the VE group after 14 days, but released less nickel and chromium (p < 0.05) after 7 days and less chromium and iron (p < 0.05) after 21 days. The SEM analysis revealed alterations on surface topography of conventional and self-ligating brackets. Conclusions: The aging process in self-ligating brackets was not greater than in conventional brackets from the same manufacturer. The null hypothesis was accepted. .

Objetivo: testar a hipótese nula de que o processo de envelhecimento em braquetes autoligáveis não é superior ao de braquetes convencionais. Métodos: Vinte e cinco braquetes metálicos convencionais (GN, 3M/Unitek; GE, GAC; VE, Aditek) e 25 autoligáveis (SCs, 3M/Unitek; INs, GAC; ECs, Aditek) de três fabricantes (n = 150) foram submetidos ao envelhecimento em solução de NaCl à temperatura constante de 37 ± 1ºC, durante 21 dias. O conteúdo de íons níquel, cromo e ferro na solução coletada com 7, 14 e 21 dias foi quantificado por meio de espectrofotometria de absorção atômica. Depois de completado o processo de envelhecimento, os braquetes foram analisados com microscópio eletrônico de varredura (MEV), em magnificações de 22x e de 1.000x. Resultados: comparando-se a liberação de metais por braquetes autoligáveis e convencionais do mesmo fabricante, observou-se que o grupo SCs liberou mais níquel (p < 0,05) que o grupo GN após 7 e 14 dias, mas menos cromo (p < 0,05) após 14 dias e menos ferro (p < 0,05) nos três períodos experimentais. O grupo INs liberou menos ferro (p < 0,05) que o grupo GE após 7 dias, e menos níquel, cromo e ferro (p < 0,05) após 14 e 21 dias. O grupo ECs liberou mais níquel, cromo e ferro (p < 0,05) que o grupo VE após 14 dias; entretanto, liberou menos níquel e cromo (p < 0,05) após 7 dias e menos cromo e ferro (p < 0,05) após 21 dias. A análise no MEV demonstrou alterações na topografia da superfície de braquetes convencionais e autoligáveis. Conclusões: o processo de envelhecimento em braquetes autoligáveis não foi superior ao de braquetes convencionais do mesmo fabricante. A hipótese nula está aceita. .

Application of pollution indices for evaluation of heavy metals in soil close to phosphate fertilizer plant, Assiut, Egypt

Pollution indices were used to investigate the levels of heavy metal concentrations in a polluted area under the effect of fertilizer plant emissions at Manqabad, Assiut. Huge amounts of dusts, fumes and gases containing heavy metals which are released from the industrial processing activities, precipitated in the neighbouring area by the effect of meteorological factors causing soil pollution. Soil samples were taken from the area downwind of the factory and analyzed to detect concentration of heavy metals in the study area. Results of soil analysis showed that the area has been harmfully affected by the heavy metals: Cd, Cu, Pb and Zn and their average concentrations are 0.3 mg/kg, 57.0 mg/kg, 94.7 mg/kg and 80.7 mg/kg respectively. These values exceeded the concentrations in soil background [0.013 mg/kg for Cd, 9.62 mg/kg for Cu, 5.17 mg/kg for Pb and 11.56 mg/kg for Zn] obtained from unpolluted area far from industrial activities and also exceeded the international standards for soil pollution stated by WHO. Pollution indices were developed to evaluate the levels of soil pollution with heavy metals. Index of geo-accumu!ation [Igeo], Enrichment Factor [EF], Pollution Index [PI], and Load Pollution Index [LPI], were estimated. The calculated results of contamination degree showed that the investigated area lies under the class of high pollution. In final conclusion, the investigated area is highly affected by emissions from the fertilizer plant So control measures should be applied to the fertilizer plant and the polluted soil area adjacent to the factory should be remediate

Efecto de la estacionalidad sobre el estado nutricional de Hierro, Zinc y Cobre / Effect of seasonality on nutritional status of Iron, Zinc and Copper

Food consumption and therefore the nutritional status of micro-nutrients are influenced by various factors such as seasonality. This study aimed to determine the effect of seasonality on the nutritional status of Fe, Zn and Cu in adult subjects. A longitudinal study was conducted during the months of September 2005 and August 2006. Fifty subjects of both sexes belonging to the urban area of the city of Santiago de Chile were evaluated. Blood samples were drawn during the first week of each month; serum iron, copper and zinc, hemoglobin, mean cell volume, serum ferritin, zinc-protophorphyrin and ceruloplasmin were determined. Serum copper and zinc levels showed significant seasonal variations but not serum iron. Mean cell volume, hemoglobin and ceruloplasmins were significantly lower during spring and summer while serum ferritin and zinc-protophorphyrin showed lower concentrations during autumn and winter. We conclude that during the spring and summer levels of serum iron, copper and zinc could be diminished by reduced food intake.

El consumo de alimentos y por lo tanto el estado de nutrición de los micronutrientes está condicionado por diferentes factores como la estacionalidad. El presente estudio tuvo como objetivo determinar el efecto de la estacionalidad sobre el estado nutricional de hierro, zinc y cobre de sujetos adultos habitantes de la ciudad de Santiago de Chile. Un estudio longitudinal en 50 sujetos de ambos sexos se realizó entre los meses de septiembre del 2005 y agosto del 2006. Durante la primera semana de cada mes se extrajo muestras de sangre para la determinación de hierro, zinc y cobre sérico, hemoglobina, volumen corpuscular medio, ferritina sérica zinc-protoporfirina y ceruloplasmina. Los niveles de cobre, zinc, hemoglobina, volumen corpuscular medio, y ceruloplasmina fueron significativamente menores durante primavera y verano mientras ferritina sérica y zinc-protoporfirina presentaron niveles más bajas durante otoño e invierno. Concluimos que la estacionalidad es un factor a considerar cuando se realicen mediciones de estado de nutrición de los microminerales hierro, zinc y cobre.

[Modified Fenton oxidation of pyrene in contaminated soils using iron nano oxides]

Problems related to conventional Fenton oxidation, including neccesity of having a low pH and production of considerable amounts of sludge, have prompted researchers to consider chelating agents to improve the pH operating range and iron nano-oxide particles to reduce excess sludge. The main objective of this study was to remove pyrene from contaminated soils by a modified Fenton oxidation method at neutral pH. Experiments were conducted using various concentrations of H2O2 [0-500 mM], iron nano-oxides [0-60 mM], reaction times [0.5-24 hours] and several chelating agents, namely, sodium pyrophosphate, ethylene diamine tetra-acetic acid, sodium citrate, fulvic and humic acids, to eliminate pyrene from soil [concentrations of 100-500 mg/kg]. The efficiency of removal of pyrene at an initial concentration of 100 mg/kg was 99% at the following reaction conditions: H2O2 and iron nano-oxide concentrations of 300 mM and 30 mM, respectively; pH=3; and a reaction time of 6 hours. The initial pyrene concentration of 100 mg/kg decreased to 7 mg/kg at optimum conditions using sodium pyrophosphate as the chelating agent at pH 7. The modified Fenton oxidation method, using iron nano-oxide at optimum conditions as defined in this research, is an efficient alternative for chemical remediation or pre-treatment of soils contaminated with pyrene at neutral pH

In vitro antioxidant activity of banana (Musa spp. ABB cv. Pisang Awak).

The methanolic extract of Musa ABB cv Pisang Awak was investigated for the polyphenolic contents and antioxidant activity. The total phenol and flavonoid contents of the fruit extract were found to be 120 mg gallic acid equivalents (GAE) and 440 mg quercetin equivalents (QE)/100 g of sample dry weight, respectively. The antioxidant activity of the Pisang Awak methanol extract (PAME) (20-500 µg/ml) was determined using 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity, reducing capacity, 2-2’-azinobis-3-ethylbenzothiozoline-6-sulfonic acid (ABTS) radical cation decolourization and hydroxyl radical scavenging capacity (OH·). The EC50 values of DPPH, ABTS and OH· activities of the PAME and butylated hydroxy toluene (BHT) were found to be 65 and 9 µg/ml, 29 and 6 µg/ml, 36 and 42 µg/ml respectively. The reducing capacity increased with increasing concentration (31.5-1000 mg/ml) of the fruit extract and the activity was comparable with the standard BHT. The high performance thin layer chromatography (HPTLC) analysis of the extract revealed the presence of polyphenols. The strong and positive correlations were obtained between total phenol/flavonoid contents (R2 = 0.693-1.0) and free radical scavenging ability was attributed to the polyphenols as the major antioxidants.

Heat-treated hull flour does not affect iron bioavailability in rats / Farinha de soja com casca tratada termicamente

In this study the chemical composition and iron bioavailability of hull and hull-less soybean flour from the new cultivar UFVTN 105AP was evaluated. The hemoglobin depletion-repletion method was used in Wistar rats. Soybean hull flour presented 37% more total dietary fiber and higher content of iron than hull-less soybean flour. The phytate:iron molar ratio, however, was 2-fold lower in the soybean hull flour in compared to the hull-less soybean flour. Animals fed soybean hull flour presented hemoglobin gains similar to those of the control diet group (p>0.05). The Relative Biological Values of hull and hull-less soybean flour were 68.5% and 67.1%, respectively, compared to the control group. Heat-treated soybean hull flour (150ºC/30 minutes) showed high content of iron and low phytate, which favors the iron bioavailability. Thus, the soybean hull flour is a better source of dietary fiber and iron than hull-less soybean flour at comparable bioavailabilities.

Neste estudo foram avaliadas a composição química e a biodisponibilidade de ferro das farinhas de soja com e sem casca do novo cultivar UFVTN 105AP. O método usado foi de depleção-repleção de hemoglobina em ratos Wistar. A farinha de soja com casca apresentou 37% a mais de fibra alimentar e maior teor de ferro (p 0,05). O Valor Relativo de Biodisponibilidade (VRB) da farinha de soja com casca e sem casca foram 68,5% e 67,1%, respectivamente, em relação ao sulfato ferroso (100%). A farinha de soja com casca submetida ao tratamento térmico (150ºC/30 minutos) apresentou maior teor de ferro e reduzido conteúdo de fitato, favorecendo a biodisponibilidade de ferro. Assim, a farinha de soja com casca apresentou melhor fonte de fibra alimentar e ferro do que a farinha de soja sem casca de comparável biodisponibilidade.

[Removal of phosphate from aqueous solutions by Iron Nano Particle Resin Lewatit [FO36]]

Entrance of phosphorous into the lakes leads to algae growth and eutrophication the aim of this study was to assess the efficiency of iron nano particles as a new suitable and applicable method for removal of phosphorous. In this study Lewatit FO36 resin was covered with Fe [III] nano-particles, and it was used as a new way to eliminate phosphate. Column experiments were carried out in 11 stages in fixed bed columns with constant flow rate of 9 ml/min and the empty bed contact time [EBCT] of 2.1 min. phosphate solutions with concentrations of 1 to 16 mg produced at neutral PH were used in 6 steps of experiment NaOH and NaCl solutions were used for regeneration of resin. Then the effect of competing anions, chloride, sulfate, bicarbonate and their compounds on the efficiency of the resin was assessed. Finally the efficiency of the resin for removal of phosphate from water treatment plant sewage in Ghods suburb was studied. Data were analyzed by SPSS 13 soft ware. The capacities of adsorption of phosphate, with concentrations of 1 to 16 mg, by each gram of resin were 1.31, 1.35, 1.53, 1.64, 1.7 and 1.75. The capacity of regenerated resin for removal of phosphate with a concentration of 6 mg/l was 1.6 mg for each gram of resin which showed a 8.5% decrease. The result of this study showed increased adsorptive capacity of resin with increased concentration of phosphate. Chloride, sulfate, bicarbonate ions and the combined anions had no effect on phosphate removal

[Hydrogenotrophic denitrification of water using zero valent iron Nano particles]

Nitrate is a water contaminant that can cause health problems in human and animals, in addition to eutrophication of the water body. So, Nitrate-contaminated water may be treated by treatment systems. In this study, hydrogenotrophic denitrification using hydrogen produced by Fe[0] as an electron donor to nitrate removal was evaluated to assess the feasibility of employing Fe[0] in the biological nitrate treatment. Batch experiments were conducted using 250 ml amber bottles at 20-35°C under anoxic conditions. The nitrate concentration in each reactor was 20 mg N/L and triplicate samples were prepared for the following treatment: Fe[0] plus cells, Fe[0] only, and control. The effect of Fe[+2] and temperature on nitrate reduction was evaluated. 97 percent of Nitrate was reduced within 2 day in a Fe[0]-cell reactor, while only 30% of the nitrate was abiotically reduced over 2 day at 30°C. Fe[+2], which is produced during anaerobic iron corrosion in the Fe[0]-cell system, might act as an electron donor for nitrate. Abiotic reduction and microbial reduction of nitrate was significantly affected by temperature conditions. The reduction rate decreased as the temperature deceased. This study demonstrated the potential applicability of employing Fe[0] as a source of electrons for biological nitrate reduction. Use of Fe[0] for microbial nitrate reduction can obviate the disadvantages associated with traditional biological denitrification that relies on the use of organic substrates or explosive hydrogen gas

Iron-zinc interaction during uptake in human intestinal Caco-2 cell line: Kinetic analyses and possible mechanism.

Iron and zinc interact at the enterocyte during absorption, but the mechanism(s) remain elusive. The aim was, therefore, to understand the mechanism of interaction using kinetic analyses of iron and zinc uptake, individually and in combination under normal and altered cellular mineral concentrations in human intestinal Caco-2 cell line. Striking differences in kinetic parameters were observed between iron and zinc uptake. Iron uptake followed a two-component model, while zinc uptake followed a three-component model. Iron uptake had a Km of 3.6 µM and Vmax of 452 pmol/mg protein/min, while zinc uptake had a Km of 42 µM and Vmax of 3.09 pmol/mg protein/min. Zinc dose-dependently inhibited iron uptake through mixed-inhibition but iron marginally increased zinc uptake. Cellular zinc repletion doubled iron uptake and eliminated inhibition, but zinc depletion decreased iron uptake. Iron pre-treatment had no effect on zinc uptake. Based on these results, a two-transporter model of iron uptake, comprising the apical iron uptake transporter divalent metal ion transporter-1 (DMT-1) and an unknown putative transporter was derived. This model for DMT-1 was verified by immunoblotting. These results implied that cellular zinc status profoundly influenced iron uptake and its interactions with zinc during uptake. DMT-1 might not simultaneously transport iron and zinc, providing a mechanistic basis for observed interactions.

[ study on biodegradability enhancement of landfill leachate by fenton oxidation]

Leachate is one of the landfill products and also a wastewater bearing the most advers effects on the environment. Biological methods are usually employed for treatment of young leachate [1-2 years] wich is of high concentration of organic compounds with low molecular weight. However these methods are not approprate for mature leachate [5-10years] due to having high rate of compounds with molecular weight and the presence of materials resistant to biodegradation and toxic compounds. Advanced oxidation process such as Fenton reagent used in treatment or biodegrability improvement of strong wastewater. In the present study the degrability improvement of mature leachate through oxidation fenton process in bench scale and in batch reactor has been investigated. The samples have been taken from Ahwaz landfill and factors such as initial COD and BOD, pH, BOD5/COD were studies as degradability, the amount of Hydrogen Peroxide, Fe[II], optimal reaction time and optimal pH. The highest amount of COD removal was observed in PH=3-3.5 and 90 minutes of reaction time. H2O2=29700mg/land Fe2+=16500 mg/l in [Fe2+]/[H2O2]=1/14.8 molarity ratio were obtained as optimal amounts BOD5/COD was equal to 0.38. This study indicates that Fenton oxidation enhances the biodegradability of leachate

Colour and COD removal from pulp and paper mill effluent by q Fenton's oxidation.

Colour and COD removal studies of pulp and paper mill effluent were carried out by Fenton's oxidation. Fenton's oxidation process was employed in four distinct stages interrelated to each other. In the first stage, FeSO4 concentration, pH and temperature were kept constant to determine H2O2 dose for maximum color and COD removal. In the second stage, dose of H2O2 obtained from first stage and same oxidation conditions were applied to determine the optimum FeSO4 concentration. Optimum pH, temperature and contact time were investigated in third and fourth stages considering the results of optimum doses of first and second stage. Maximum color up to 98% and COD removal up to 62% were obtained for Fenton reagents of 600 mg/L of H2O2 and 100 mg/L of Fe2+ dose at pH 3.0 for 300 min of contact period between reagents and effluent.

Review of coagulation technology for removal of arsenic: case of Chile.

Coagulation technology has been used since 1970 in northern Chile for removing arsenic from drinking-water. This experience suggests that coagulation is an effective technology for the removal of arsenic. It is currently possible to reduce arsenic from 400 microg/L to 10 microg/L at a rate of 500 L/sec, assuming pH, oxidizing and coagulation agents are strictly controlled. The Chilean experience with the removal of arsenic demonstrates that the water matrix dictates the selection of the arsenic-removal process. This paper presents a summary of the process, concepts, and operational considerations for the use of coagulation technology for removal of arsenic in Chile.

Effect of surfactants on Fenton's reagent-mediated degradation of Kraft black liquor.

One of the limitations of the biodegradation of hydrophobic chemical compounds, like lignins, is their low solubility in the aqueous solution where this process takes place. To resolve this problem, surfactants have been used to improve the solubility of these hydrophobic compounds. In this investigation, we studied the effect of surfactants (anionic, cationic, and non-ionic) on the treatment of Kraft black liquor with Fenton's reagent. In the Fenton reaction, H2O2 (two different concentrations, 10 mM and 20 mM), FeCl2 (1 mM) and surfactant solution (10%) were used. Black liquor degradation was determined by UV/Visible spectrophotometry and by measuring phenolic groups. In the presence of Fenton's reagent, the optimum conditions for the oxidative degradation of black liquor were 10 mM H2O2, 1 microL of 10% solution of anionic surfactant (SDS). The importance of the use of surfactants for preparing black liquor for subsequent Fenton's reagent-mediated degradation was discussed.

Electrochemical oxidation of pharmaceutical effluent using cast iron electrode.

Electrochemical oxidation of low (BOD/COD) ratio pharmaceutical wastewater was investigated in this study, using cast iron electrode. The batch experimental results were assessed in terms of COD and BOD concentration while the recalcitrance was monitored in terms of change in the (BOD/COD) ratio during the process. The effects of operating parameters like pH, electrolysis duration and current density were studied on the treatment efficiency and their operating ranges were experimentally determined. The efficiency and energy consumption of anode were estimated. Cast iron electrode has been found to be effective in removing 72% COD after 2hours of electrolysis. In particular, it was found that the (BOD/COD) ratio had improved from 0.18 to 0.3 after 120 min. of electrolysis indicating improvement of biodegradability of wastewater. It has been found, the pharmaceutical wastewater could be effectively pretreated by anodic oxidation.

FTIR study of some Egyptian bentonitic clays

The miocene clay deposits at G. Hamza- G. Um Qamar off the Cairo Ismailia Road are texturally classified as silt bearing, clay-rich mudstones. X-Ray powder diffraction analysis indicates that the main clay minerals present are montmorillonite and kaolinite. Urn Qamar mudstones contain higher percentages of montmorillonite and lower proportions of Kaoloinite than those of G. Hamza. The IR absorption bands of these clay minerals in the OH and Si-O stretching regions, as well as those in the OH and Si-O bending regions have been studied in detail. The FTIR analysis indicates that Mg[II] and Fe [II] are present in minor amounts in the montmorillonite structure

Batch kinetic modeling of arsenic removal from water by mixed oxide coated sand (mocs).

A new granular media developed by coating of iron and manganese on quartz sand surface proved to be effective for arsenic (III) removal from water. The media has shown alkali resistance. The kinetic and thermodynamic studies data were tested using pseudo-second- order, intraparticle diffusion and Elovich equation models. The rate constants, equilibrium sorption capacity and normalized standard deviations were calculated for all the three models. It was shown that all three models almost accurately predict the sorption capacity with respect to time for whole range of data points. However, sorption kinetic data were better correlated using Elovich equation model based on normalized standard deviation. The Langmuir and Freundlich isotherm equations could be used to describe the partitioning behavior of system at different pH and media size. The results of thermodynamic studies show that the As(III) adsorption on Mixed Oxide Coated Sand (MOCS) was endothermic in nature. Kinetic and isothermal studies data have also been used to obtain thermodynamic parameters of the process.