Personal Research Database

Deshicar, A.M., Bokade, S.S. and Dara, S.S. (1990), Modified hardwickia binata bark for adsorption of mercury(II) from water. Water Research, 24 (8), 1011-1016.

Full Text: W\Wat Res24, 1011.pdf

Abstract: Hardwickia binata bark was found to have a good sorption capacity for mercury(II). Colour leaching can be prevented and the physical characteristics of the bark can be improved by treatment with formaldehyde in acidic medium. Studies indicated that the sorption of Hg(II) increases as the pH increases and a contact time of 2 h was found to be optimum. The effect of concentration shows that modified bark can remove most of the Hg(II) from water if its concentration is below 20 mg/l and sorption of mercury conformed to the Freundlich adsorption isotherm. The presence of light metal ions interferes with the sorption of mercury. Mg(II) at a concentration of 200 mg/l interferes with sorption to a maximum extent. Among the different anions, it was observed that sorption of mercury was maximum for acetate and nitrate (97%). The break-through sorption capacity determined by conducting a column experiment was observed to be 21 mg/g.

Keywords: Mercury Removal, Wastewater Treatment, Bark; Sorption

Chen, X.H., Gosset, T. and Thévenot, D.R. (1990), Batch copper ion binding and exchange properties of peat. Water Research, 24 (12), 1463-1471.

Full Text: W\Wat Res24, 1463.pdf

Abstract: Cupric ion fixation by raw peat is likely involved in both cation exchange with H⁺, Ca²⁺, Mg²⁺ and adsorption-complexation, i.e. fixation of the same equivalent of copper ions and anions (NO₃^-) without any ion release. The importance of both reactions depends largely on initial copper concentration, peat type and pH. Isotherms of copper (initial concentration ranging between 1 and 20 mM) fixation on two types of peat (eutrophic and oligotrophic peat at 30 g d.w./l at pH ranging between 2 and 4) showed that the higher the initial cupric concentration, the more important is this complexation reaction; over this initial cupric concentration range, ion exchange sites were relatively saturated and reached 308 and 101 mmol/kg d.w. for eutrophic and oligotrophic peat whereas no saturation was found for complexation sites, their capacity attaining up to 74 and 119 mmol/kg d.w., respectively.

The apparent equilibrium constant for ion exchange with acid-treated peat (initial pH 4.0, 30 g d.w./l) for various metal binding on both peat sites ranged between 1.1 and 10.8 in 15 mM metallic solutions. The apparent affinity in batch conditions for 5 elements may be compared according to the apparent global equilibrium constants, ranging between 1.1×10^-6 and 20.2×10^-6: Pb > Cu > Ca > Mg, Zn for eutrophic peat and Pb > Ca > Cu > Mg, Zn for oligotrophic peat.

Keywords: Peat, Metal Cation, Ion Exchange, Adsorption, Complexation Equilibrium, Electroneutrality, Soil Organic-Matter, Kinetics, Acid

? Joglekar, H.S., Samant, S.D. and Joshi, J.B. (1991), Kinetics of wet air oxidation of phenol and substituted phenols. Water Research, 25 (2), 135-145.

Full Text: 1991\Wat Res25, 135.pdf

Abstract: Wet air oxidation (WAO) of aqueous solutions of phenol and substituted phenols namely, omicron-, m- and p-chlorophenols, omicron-, m-cresols, omicron- and p-methoxyphenols, omicron-ethylphenol and 2,6-dimethylphenol, were carried out. The process was studied in a 1 litre stainless steel autoclave at temperatures in the range of 150-180-degrees-C. The oxygen partial pressure was varied from 0.3 to 1.5 MPa and the initial phenol concentration was 200 mg/l.

The oxidation of phenols in water involves a free-radical mechanism and proceeds in two steps. The oxidation reaction was found to be first order in oxygen and also first order with respect to phenolic substrates in both steps. The values of activation energy were found to be in the range of 12.410³-20110³ kJ/kmol. The conditions have been found under which the overall oxidation reaction becomes reaction controlled or mass transfer controlled. The values of mass transfer coefficient have been obtained. The data based on bench scale shows wet air oxidation of phenols can achieve destruction efficiencies exceeding 99.9%. The reduction of COD during oxidation of all phenols was also measured. Greater than 90% COD reduction was achieved. Some aspects of the process design of the oxidation reactor have been discussed.

Keywords: Wet Air Oxidation, Phenols, Cod Reduction, Kinetics, Effluent Treatment, Mass Transfer Coefficient At High Temperature and Pressure, Catalytic-Oxidation, Copper Oxide, Phase, Reactors

Christoffersen, J., Christoffersen, M.R., Larsen, R. and Moller, I.J. (1991), Regereration by surface-coating of bone char used for defluoridation of water. Water Research, 25 (2), 227-229.

Full Text: W\Wat Res25, 227.pdf

Abstract: A bone char column used to defluoridate water can be very simply and repeatedly regenerated without significant loss of binding capacity for fluoride or of efficiency. The regenerating solution contains calcium chloride and sodium dihydrogen phosphate with pH adjusted to about 3. The regenerating solution can also be produced by dissolving the present waste part of the bone char product, which is too finely powderized for use in the column, in dilute hydrochloric acid. During regeneration, most of the pre-adsorbed fluoride is retained by the bone char and the precipitating phase is apatitic. The ‘regeneration’ is thus a surface-coating process.

Keywords: Defluoridation, Water, Bone Char, Regeneration, Fluoride, Surface-Coating

El-Geundi, M.S. (1991), Clour removal from textile effluents by adsorption techniques. Water Research, 25 (3), 271-273.

Full Text: 1991\Wat Res25, 271.pdf

Abstract: The adsorption of two basic dyestuffs (Atrazon Blue and Maxilon Red) and two acid dyestuffs (Telon Blue and Erionyl Red) onto maize cob was studied. High adsorptive capacities were observed for the adsorption of basic dyestuffs, namely, 160 and 94.5 mg dye per g maize cob for Astrazon Blue and Maxilon Red, respectively. Lower capacities were obtained with the acid dyestuffs, namely, 47.7 and 41.4 mg dye per g maize cob for Erionyl Red and Telon Blue, respectively. A series of contact-time experiments was undertaken in an agitated batch adsorber to assess the effect of the system variables, namely, agitation speed, maize cob particle size and maize cob mass. The experimental results for these contact-time experiments were discussed.

Keywords: Dyestuffs, Maize Cob, Adsorption Capacity, Adsorption Rate

Notes: IIsotherm

Weber, Jr., W.J., McGinley, P.M. and Katz, L.E. (1991), Sorption phenomena in subsurface systems: Concepts, models and effects on contaminant fate and transport. Water Research, 25 (5), 499-528.

Full Text: W\Wat Res25, 499.pdf

Abstract: The behavior, transport and ultimate fate of contaminants in subsurface environments may be affected significantly by their participation in sorption reactions and related phenomena. The degree to which the resulting effects can be quantified and predicted upon the extent to which certain fundamental aspects of sorption are understood, and upon the accuracy with which these phenomena can be characterized and modeled in complex subsurface systems. Current levels of understanding of the reactions and processes comprising sorption phenomena are discussed in this paper, as are the forms and utilities of different models used to describe them. Emphasis is placed on concept development, on the translation of these concepts into functional models for characterizing sorption rates and equilibria, and on the application of these concepts and models for explaining contaminant behavior in subsurface systems. Examples are provided to illustrate the impacts of sorption phenomena on contaminant transport.

Keywords: Sorption, Partitioning, Soils, Groundwater, Subsurface Systems, Rate and Equilibrium Models, Mass Transfer, Contaminant Transport, Dispersed Organic Polymers, Natural Solids, Porous-Media, Groundwater, Water, Soil, Adsorption, Surface, Interface

Richard, F.C. and Bourg, A.C.M. (1991), Aqueous geochemistry of chromium: A review. Water Research, 25 (7), 807-816.

Full Text: W\Wat Res25, 807.pdf

Abstract: The aqueous geochemistry of chromium is reviewed, especially with reference to the recent work of Rai et al. (Report EPRI EA-4544, 1986, Report EPRI EA-5741, 1988). The chromium content of natural waters is generally low whereas rocks exhibit a wide range of Cr concentrations. In natural environments, the most stable oxidation states of chromium are Cr(III) and Cr(VI). The following minerals can control the dissolved chromium content of natural waters: Cr(OH)_3(s) and (Fe, Cr)(OH)₃ (ss) for Cr(III). Major Cr(III) disolved species are CrOH²⁺ and Cr(OH)₃(0), as well as several organic and a few inorganic complexes, whereas HCrO^4-and CrO₄^-2 are the main forms of Cr(VI) in natural waters. The chromium distribution is also controlled by redox processes. Oxidation of Cr(III) to Cr(VI), poor with dissolved oxygen, is very effective in the presence of solid MnO₂. Fe(II)-and organic matter-rich environments favour the reduction of Cr(VI) to Cr(III). Interaction with solid phases can also regulate the chromium content of water. Cr(III) exhibits a typical cationic sorption behaviour. Its adsorption increases with pH, but decreases when competing cations are present. Chromium(VI), on the other hand, exhibits a typical anionic sorption behaviour. Its adsorption decreases with increasing pH and when competing dissolved anions are present.

The migration of chromium is determined by the competition between complexation, dissolution/precipitation, redox processes and adsorption/desorption mechanisms. Cr(III) will migrate under acidic conditions and/or if present as dissolved organic matter complexes. Hexavalent chromium generally migrates rapidly but its mobility is inhibited when the Fe(II) and organic matter concentrations are high and when sorption processes are favoured (low pH).

Keywords: Chromium, Geochemistry, Natural Waters, Review, Minerals, Oxidoreduction, Adsorption, Migration, Water-Soluble Chromium(V), Sea-Water, Chronium Speciation, Hexavalent Chromium, Chemical Speciation, Organic Materials, Soils, Adsorption, Behavior, Iron

Yaacoubi, A., Mazet, M. and Dusart, O. (1991), Competitive effect in bi-solute adsorption onto activated carbon: DSS, alcohols and phenols as solutes. Water Research, 25 (8), 929-937.

Full Text: W\Wat Res25, 929.pdf

Abstract: Many organic toxic compounds in water supplies are resistant to conventional treatment. For low concentrations of organic contaminants, activated carbon is a good adsorbent and its use for water supplies has been widely studied. Bath experiments are generally used for the prediction of performance such as adsorptive capacity of granular activated carbon filters. To simulate the adsorption process, studies have been carried out with alcohols (Abe et al., 1979, 1980; Gaid et al., 1983; Belfort, 1979), in a mixture with another organic solute, LaFrance et al. (1983), Dusart et al. (1990), Martin and Albahrani (1977, 1979) have investigated equilibrium expressions and different constants for multisolute adsorption on activated carbon.

The purpose of this work is to study the adsorption kinetic evolution for sodium dodecylsulphate in the presence of n-alcohols (methanol to pentanol) and n-dodecanol and to examine the steric hindrance influence for the adsorption equilibrium parameters and the external mass transfer coefficient K_f [equation (1)].

Also, aromatic molecules such as phenol and 2-naphthol have been chosen to be compared to alcohols in their co-adsorption with the DSS in order to have a better knowledge of the surface heterogeneity of the activated carbon. Then, the maximal adsorption capacity GAMMA infinity is determined from the Langmuir isotherm equation. A 3 h contact time is required for the obtention of the equilibrium DSS adsorption; this stabilization in the rapid phase of the adsorption is more rapidly achieved in the presence of a co-adsorbate. The effect of the alcohols studied in the millimolar range: methanol, ethanol, propanol, butanol, pentanol at equilibrium time is shown in Fig. 1-the dimensionless adsorbed concentration C/C₀ is unchanged for methanol and ethanol but diminished in the other cases.

The low solubility of pentanol in water seems to be a limiting factor for this study; so that the dodecanol is solubilized in methanol before being added to water solutions of DSS. The micromolar range of dodecanol is sufficient to strongly diminish DSS adsorption on activated carbon (Fig. 2). K(f) evolution is of the same order. The large steric hindrance and hydrophobic effects of the chain of dodecanol and its equally good adsorbability (Schwuger and Smolka, 1977) give competitive phenomena in the co-adsorption of the DSS. A compact molecule such as phenol or 2-naphthol is compared to these results (Figs 3 and 4). The sequence of the added co-adsorbates in the adsorption can modify the kinetic external mass transfer coefficient and also the pseudo equilibrium parameters are important to obtain the CAG filter performance.

The influence of Ca²⁺ ions, which are very important for DSS fixation onto the negative charged surface of the CAP (Mazet et al., 1988), is also studied. The results of the adsorption of DSS in the presence of phenol, naphthol (N₂) are noted on Fig. 3. No phenol effect on DSS appeared. The N₂ presence somewhat diminishes the adsorption of DSS (Fig. 5) and desorbs the DSS when it is added after 3 h adsorption contact time (Fig. 6) but, K_f valiues are not modified (Fig. 7). Ca²⁺ ions give, and maintain good promotion of the adsorption of DSS only if simultaneously present with the DSS (Figs 5 and 6). The complex DSS-Ca²⁺ seems to be necessary to have supplementary sites on the carbon surface.

For N₂ adsorption in the presence of DSS (Figs 8, 9 and 10), an inhibition effect can be observed; K_f is also diminished and if the DSS-Ca²⁺ mixture is first adsorbed, a stronger inhibition of the adsorption is noted (K_f is reduced in the same order). In this case an inhibition effect is obtained which is reflected in the evolution of the maximum capacity results (Fig. 11).

Keywords: Adsorption, Activated Carbon, Surfactants, Alcohols, Phenols, Water Treatment, Gas-Liquid-Chromatography, Organic-Compounds, Aqueous-Solution

Cohen, A.D., Rollins, M.S., Zunic, W.M. and Durig, J.R. (1991), Effects of chemical and physical differences in peats on their ability to extract hydrocarbons from water. Water Research, 25 (9), 1047-1060.

Full Text: W\Wat Res25, 1047.pdf

Abstract: This paper reports on the first phase of a project designed to determine the potential of peats in extracting hydrocarbons from groundwater. Peat samples with markedly different compositions were slurried under controlled conditions in either saturated solutions or emulsions of benzene, toluene, or m-xylene. All peats were characterized in order to determine the possible correlation between various parameters and extraction capacities. All peats were found to be capable of extracting substantial amounts of either free-phase or dissolved hydrocarbons from water. Free-phase extraction ranged from 30 to 50% of the starting wet volume of the peats. Solution extraction produced reductions in concentrations of between 53 and 97%, depending on the peat type. In solution, toluene was found to be more slowly adsorbed than either benzene or m-xylene. In general, the best hydrocarbon adsorption from solution can be achieved by using peats that are low in fiber and birefringent organics and high in ash and guaiacyl lignin pyrolysis products.

Keywords: Peat, Hydrocarbons, Oil, Underground Storage Tanks, Chromatography-Mass-Spectrometry, Pyrolysis

? Takács, I., Patry, G.G. and Nolasco, D. (1991), A dynamic model of the clarification-thickening process. Water Research, 25 (10), 1263-1271.

Full Text: 1991\Wat Res25, 1263.pdf

Abstract: A dynamic model of the clarification-thickening process is presented. Based on the solids flux concept and on a mass balance around each layer of a one-dimensional settler, this model can simulate the solids profile throughout the settling column, including the underflow and effluent suspended solids concentrations under steady-state and dynamic conditions. The model makes use of a special settling velocity equation designed to simulate the settling velocity of dilute and more concentrated suspensions. The model can be applied to both primary and secondary settlers to simulate dynamic and steady-state conditions. Examples based on full-scale and pilot-scale experimental data taken from the literature serve to illustrate the application of the model to secondary settlers. Results of the analysis confirm that the model can serve to predict the effluent and underflow suspended solids concentrations under a variety of conditions.

Keywords: Clarifications, Dynamic Modeling, Hindered Settling, Steady-State Analysis, Solids Flux Analysis, Thickening

Rhodes, M.W. and Kator, H.I. (1991), Use of Salmonella-typhimurium WG49 to enumerate male-specific coliphages in an estuary and watershed subject to nonpoint pollution. Water Research, 25 (11), 1315-1323.

Full Text: W\Wat Res25, 1315.pdf

Abstract: The occurrence of male-specific RNA (FRNA) coliphages, proposed as indicators of enteric viruses, was determined in an estuary subject to nonpoint pollution that included fecal inputs from livestock. A host originally developed for detecting FRNA phages in sewage was applied to water and sediment samples. Phages were enumerated using the host Salmonella typhimurium WG49 containing an Escherichia coli plasmid coding for sex pili, and the female parent strain WG45. FRNA phages and fecal coliforms were enumerated in samples collected seasonally from an estuary and associated feeder streams and densities related to selected environmental parameters. Mean phage densities enumerated on WG49 ranged from < 1 to 50 100 ml^-1 water and < 13 to 7200 100 g^-1 dry sediment. Examination of 300 phages from estuarine and freshwater samples showed that greater-than-or-equal-to 99% were RNase-resistant, greater-than-or-equal-to 94% were lytic to the female parent salmonella strain (WG45), less-than-or-equal-to 9% were lytic to male E. coli C3000, and none were lytic to female E. coli C. RNase resistant phages lytic to both salmonella strains were noncontractile flexible tailed phages and those lytic to male salmonella or E. coli hosts were filamentous phages. Electron micrographs of the only RNase-sensitive phage recovered that plaqued only male hosts showed cubic phage particles adsorbed to sex pili. Parallel enumerations of environmental samples on WG45 and WG49 yielded equal or greater phage densities on the former host. Purified phages from these samples were lytic to certain salmonella serovars recovered from the environment but did not cross react with fecal coliform or heterotrophic bacteria isolated from the environment. Although the WG49 host was inappropriate to estuarine and freshwater samples examined because of interference by somatic phages, WG45 and WG49 should be examined as hosts for enumerating salmonella phages. Similarly, the public health significance of somatic phages detected by these hosts should be determined. FRNA phages, with a single exception (1/187 samples), were not detected in a condemned shellfish growing area subject to nonpoint pollution. This observation questions the application of FRNA phages as indicators of fecal contamination in waters impacted by diffuse fecal inputs.

Huang, C., Huang, C.P. and Morehart, A.L. (1991), Proton competition in Cu(II) adsorption by fungal mycelia. Water Research, 25 (11), 1365-1375.

Full Text: W\Wat Res25, 1365.pdf

Abstract: Fungal mycelia have been shown to be effective adsorbents for the removal of heavy metals from dilute solutions. Copper ions and protons become adsorbed to the fungal surface through reaction with specific surface sites including amino-, phosphate, carboxyl-or hydroxo-groups. In this study, an alkalimetric/metal titration technique was used to evaluate the competitive adsorption between protons and Cu(II) ions onto acid-washed mycelia of Aspergillus oryzae and Rhizopus oryzae. A general macroscopic mechanism has been established to describe the specific adsorption of both protons and Cu(II) ions. Using a simple graphic or a non-linear least squares technique, the adsorption parameters; i.e. adsorption constant and maximum adsorption capacity, were evaluated. The results predicted by the two-site model with a double reciprocal plot or the Scatchard plot were compared by non-linear regression. In the presence of multiple classes of sites, better fit of the experimental data was obtained by treating the fungal surface as one which possesses two major functional groups, namely: (1) high affinity of monodentate binding, (2) low affinity of bidentate binding. Because hydrogen ions compete significantly with Cu(II) ions for adsorption sites, the competitive Langmuir isotherm so derived was characterized by three parameters: two-site Cu(II) affinity, two-site Cu(II) adsorption density and apparent proton affinity. This enabled differentiation of the Cu(II) adsorption from protons. Two intrinsic equilibrium constants for Cu(II) surface complexation were estimated. With this information, it was possible to predict the adsorption of Cu(II) over a wide range of metal loading conditions at various pH values.

Keywords: Biosorption, Adsorption, Langmuir Adsorption Isotherm, Copper, Fungus, Aspergillus-Oryzae, Rhizopus-Oryzae, Dilute Aqueous-Solutions, Metal-Ions, Surfaces, Removal, Binding, Model

Mathavan, G.N. and Viaraghavan, T. (1992), Coalescence/Filtration of an oil-in-water emulsion in a peat bed. Water Research, 26 (1), 91-98.

Full Text: W\Wat Res26, 91.pdf

Abstract: Breakdown mechanisms and flow characteristics involved in a peat bed treating oil-in-water emulsions have not yet been understood fully. This paper examines the applicability of the well-known Carman-Kozeny filtration equation to a 1000 mm peat bed treating a standard mineral oil-in-water emulsion at six different flow rates. The specific permeability coefficient, the Carman-Kozeny constant and the shape factor of peat were found to be 5.3×10^-11 m², 3.4 and 2.2, respectively.

Assuming the impaction-interception mechanism to predominate, the overall coalescence efficiency of the peat bed was evaluated. The effects of flow rates and depths of peat bed on coalescence efficiency were analyzed. Contrary to the general trends observed by other investigators, coalescence efficiency decreased with an increase in bed depth (from 14% at 200 mm depths to 3% at 1000 mm depth) indicating possible simultaneous occurrence of filtration and coalescence in the peat bed.

Keywords: Coalescence, Filtration, Oil-In-Water Emulsion, Peat, Oily Wastes, Emulsions

Fu, G. and Allen, H.E. (1992), Cadmium adsorption by oxic sediment. Water Research, 26 (2), 225-233.

Full Text: W\Wat Res26, 225.pdf

Abstract: To understand the strong pH dependency of cadmium adsorption by oxic sediment, we investigated the surface charge of sediment particles by potentiometric titration with acid and base. Metal adsorbed by sediment can occur by complexation of metal ions with weakly acidic functional groups or by ion exchange of metal ions. A multi-site binding model, which incorporates the effect of pH, has been applied to describe the adsorption of cadmium onto sediment. The model has been used to satisfactorily predict the extent of adsorption over the pH range of 4.5-7.0.

Keywords: Adsorption, Cadmium, Sediment, pH, Multisite Model, Trace-Metals, Complexation, Speciation, Matter, Water, Model

Hewitt, C.N. and Rashed, M. (1992), Removal rates of selected pollutanta in the runoff waters from a major rural highway. Water Research,