Preliminary Batch Experiments Research Articles

Amendments of waste ochre from former coal mines can potentially be used to increase soil carbon persistence

There is an increasingly urgent need to remove CO2 from the atmosphere. Increasing C storage in soils has been discussed as a possible method of achieving this. Regardless of whether increasing soil C would result in reduced atmospheric C or not, increasing the amount of organic carbon (OC) stored as organic matter in soils is widely regarded as leading to agronomic benefits such as increased water retention and resistance to erosion. Fe oxides adsorb OC in soil, protecting it from degradation. In this study we investigated the use of waste ochre (Fe oxy-hydroxide) that precipitates from the drainage of former coal mines as a soil amendment to increase C storage in soils via reduced C lability. In preliminary batch experiments, ochres reduced the release of OC from soils into solution. In plant growth experiments with wheat (var. Skyfall, RAGT) 5 wt% amendments of ochre to soils significantly reduced the concentration of hot water extractable OC by approximately 16% and OC lost from the soils in leachate by approximately 43%. Above ground plant biomass was significantly reduced by approximately 50% in the amended soils. There was no evidence for increased uptake of potentially toxic elements in the plants from the ochre-amended soils compared to the study controls but Olsen P extractable phosphate was decreased by the ochre amendments. In subsequent experiments with agronomically realistic additions of KH2PO4 there was no difference in plant biomass between the study controls and the ochre-treated soils suggesting that reduced plant growth was due to reduced P availability; C lability was still significantly reduced. Furthermore, the ochre amendments helped retain th added phosphate in the soil. These results indicate that Fe oxide amendments to soil may be a viable way of changing soil chemistry in order to increase the amount of OC retained in soils. Further experiments investigating the impacts of the ochre amendments on greenhouse gas emissions and soil biology are required followed by field trials where the impact of more variable soil moisture and temperature effects can be assessed and crops grown to harvest. A full Life Cycle Analysis could then be performed. Given the relatively limited quantities of former coal mine ochres available in the UK and the carbon footprint of transporting materials prior to adding them to soils, similar experiments to those reported here, taking into account chemical and mineralogical variations, are warranted to determine the global stock pile of Fe-rich wastes that could potentially be used to reduce C lability in soils.

Mechanochemically sulfidated zero-valent iron as persulfate activation catalyst in permeable reactive barriers for groundwater remediation – A feasibility study

The technology of permeable reactive barriers is reliable and economically effective to prevent the spread of pollutants in groundwaters. Yet, it is efficacious only with easily reducible chemicals such as heavy metals and halogenated organics. In the present study, sulfidated zero-valent iron solventless synthesized by ball-milling is proposed as a possible barrier filling for activation of persulfate to achieve sound removal of reduction-resistant organic pollutants (the herbicide atrazine was used as a model pollutant). Preliminary batch experiments demonstrated rapid degradation of atrazine. Continuous experiments executed in columns proved the superior efficiency of sulfidated iron as a persulfate activator, compared to zero-valent iron, in terms of removal of both atrazine and byproducts. Optimal atrazine removal in the column was achieved with 10% sulfidated iron packing, and 9 mM persulfate at a hydraulic residence time of 6.02 h. Under such conditions, the estimated bed length of the reactive barrier for 99% atrazine removal was 8.69 cm. The morphology and surface-active species in the column demonstrated that activation of persulfate mainly occurred at the inlet of the column until the complete usage of the active species. Batch experiments with coexisting ions suggested that they have a minor influence on atrazine removal percentage, while Mg2+, Ca2+, CO2− and HCO− had a significant impact on the kinetics of the process. However, analogous column experiments demonstrated that the coexisting ions have a negative influence on both atrazine and its byproducts. The results obtained in this study corroborate the potential application of persulfate-enhanced permeable reactive barriers for in situ removal of atrazine from underground water.

Microwave-enforced green synthesis of novel magnetic nano composite adsorbents based on functionalization of wood sawdust for fast removal of calcium hardness from water samples.

Developing new generation of adsorbents for water treatment to reduce calcium hardness and producing high quality water is important and continuous trend. This manuscript is devoted with this direction. Thus, two novel magnetic nanocomposite adsorbents were synthesized by covalently binding of tartaric acid (TA) and citric acid (CA) to wood sawdust coated magnetic nanoparticles (WSD@Fe3 O4 NPs) using green microwave solvent-less technique. The adsorbents thus prepared WSD@Fe3 O4 NPs-TA and WSD@Fe3 O4 NPs-CA were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Preliminary batch experiments were performed to evaluate percentage of Ca(II) adsorbed by the bare WSD@Fe3 O4 NPs and its functionalized forms by TA and CA, as a function of pH (initial concentration 80mg/L), indicated 59.5%, 84.70%, and 99.29%, respectively, at pH 7 as optimal value. To attain maximum adsorption capacity, effect of adsorbent dosage and contact time were also optimized for the two modified adsorbents. Accordingly, Ca(II) adsorption capacity was determined to be 18.4mg/g as exhibited by WSD@Fe3 O4 NPs-TA. However, WSD@Fe3 O4 NPs-CA showed higher capacity value recorded to be 27.2mg/g. The novel adsorbents were successfully applied for fast reduction of calcium hardness from real water samples, during 15-20min and via two consecutive in situ batch operations. PRACTITIONER POINTS: This manuscript aims to minimize Ca(II) hardness in aqueous solutions by performing magnetic separation under external magnetic field. WSD was magnetized using Fe3 O4 then modified by using safe organic modifiers using of the benefits of solvent-less microwave radiation technique for adsorbent synthesis and functionalization. Two novel environmentally magnetic nanocomposites WSD@Fe3 O4 NPs-TA and WSD@Fe3 O4 NPs-CA were checked on real water samples.

Optimization and Single-Stage Centrifugal Contactor Experiments with the Novel Hydrophilic Complexant PyTri-Diol for the i-SANEX Process

ABSTRACTThe applicability of 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl)]pyridine (PyTri-Diol) in the innovative Selective ActiNide EXtraction (i-SANEX) process as water-soluble complexing agent was studied. Preliminary batch experiments were aimed at identifying the optimal formulation of the PyTri-Diol solution and at preparing the ground for single-stage centrifugal contactor experiments. A N,N,N′,N′ tetraoctyl diglycolamide (TODGA)-based solvent loaded using a spiked synthetic Plutonium and Uranium Reduction EXtraction raffinate and the optimized PyTri-Diol aqueous phase were contacted in a single-stage annular centrifugal contactor setup with three different flow-rate conditions. No hydrodynamic problems were encountered, and promising minor actinide separation from other cations was achieved with satisfactory kinetics and stage efficiency. The flow sheet of a TODGA–PyTri-Diol-based i-SANEX process was designed exploiting batch and single-stage data, promoting the CHON compliant PyTri-Diol as excellent alternative to the formerly used SO3–Ph–BTP.

TREATMENT OF MUNICIPAL WASTEWATER WITH CALCIUM PHOSPHATE: A NEW PHYSICOCHEMICAL PURIFICATION STEP

An apatitic calcium phosphate gel (HaG) was elaborated and used to treat municipal wastewater in a physicochemical cycle prior to the standard biological degradation process. Preliminary laboratory batch experiments outlined the kinetics of heavy metal sorption by monitoring the concentrations found in filtered fractions as a function of treatment time. On site experiments were performed in a municipal wastewater treatment plant by derivation of real wastewater into an experimental tank. In this case, the sorption of organic and metal pollution was studied on the whole effluent. The solid and liquid phases were both characterized using elemental analysis, total and organic carbon, and thermal analysis of the solids collected. Results showed significant reductions in heavy metal contents of about 50 to 60% for main metals such as lead, aluminum and iron in the liquid phase. The concentrations went respectively from initial values of 0.07, 0.15 and 1.80 ppm to 0.04, 0.11 and 0.03 ppm in the treated waters for these elements. Organic matter also reacted with the HaG by adsorbing to the solid particles, with the contents of organic carbon increasing from zero to 80 g/Kg on the solids and decreasing from 130 ppm to 24 ppm in the liquid phase. This allows foreseeing improvements in the biological treatment process following this physicochemical purification step. The elemental analysis showed that up to 50 and 90 percent of the heavy metals could be removed from the effluent. The presence of the organic matter adsorbed on calcium phosphate was confirmed by thermal methods.

Enhanced Spore Production of <i>Bacillus subtilis</i> Grown in a Chemically Defined Medium

Spores of Bacillus subtilis are being used as probiotics and competitive exclusion agents for animal consumption. Commercial production media often include relatively expensive components of animal origin that are a potential source for the presence of adventious agents, therefore undesirable for use in production scale. In this study a new animal-free component, chemically defined medium, was tested for B. subtilis spore production. Medium composition was optimized with respect to vitamin composition, carbon, nitrogen and calcium concentrations. A fed-batch bioprocess was developed, being the effect on sporulation of the carbon to nitrogen ratio at the end of the exponential growth phase studied. The developed strategy consisted of an initial and a final batch phase and an intermediate fed-batch phase with the addition of a feeding solution containing glucose and calcium and the addition of a feeding solution of ammonium sulphate, using an exponential and a constant feeding profile, respectively. Using the fed-batch strategy, it was possible to achieve a maximum spore production of 3.6 × 1010 spores/mL, corresponding to a 5 folds increase when compared to the preliminary batch experiments.

Development of Bench‐Scale Bio‐Packed Column for Wastewater Treatment from Optical Emission Spectrometry

AbstractAn eco‐friendly and inexpensive technique for wastewater treatment originated from inductively coupled plasma‐optical emission spectrometry (ICP‐OES) is presented within this paper. The proposed process comprised of loading waste crab shells in packed column for adsorption of heavy metal ions, followed by desorption using 0.01 M HCl. An exhaustive physical and chemical characterization of ICP‐OES wastewater revealed the complex nature of effluent, including the presence of 15 different metals and metalloid under strong acidic condition (pH 1.3). Based on the preliminary batch experiments, it was identified that solution pH played a major role in metal sequestration by crab shell with pH 3.5 identified as optimum pH. Rapid metal biosorption kinetics along with complete desorption and subsequent reuse for three cycles was possible with crab shell‐based treatment process. Continuous flow‐through column experiments confirmed the high performance of crab shell towards multiple metal ions with the column able to operate for 22 h at a flow rate of 10 mL/min before outlet concentration of arsenic reached 0.25 times of its inlet concentration. Other metal ions such as Cu, Cd, Co, Cr, Pb, Ni, Zn, Mn, Al, and Fe were only in trace levels in the treated water until 22 h. The performance of the treatment process was compared with trade effluent discharge standards, and the process flow diagram along with cost analysis was suggested.

High efficiency canthaxanthin production by a novel mutant isolated from Dietzia natronolimnaea HS-1 using central composite design analysis

The bacterium Dietzia natronolimnaea HS-1 is biotechnologically important due to its ability to biosynthesis the pigment canthaxanthin (CX). This study presents a promising direction to attain to the highest feasible levels in biomass dry weight (BDW), total carotenoid (TC) and CX by using the selection of superior mutant type in combination with optimization of nutrient medium components. The mutant strains were obtained using UV irradiation and ethyl methane sulfonate (EMS) treatment. Results showed that the mutants induced by EMS had higher survival and growth rates compared to UV mutants. EMS was effective mutagenic agent for strain improvement of D. natronolimnaea HS-1 for enhanced CX productivity. Also, preliminary batch experiments were carried out to achieve the suitable conditions for CX production analysis and found that d-glucose, mannose and Fe3+ have significant influences on the CX biosynthesis and microorganism growth. The medium formulation in a batch bioreactor was optimized by a central composite design-response surface methodology (CCD-RSM). Second-order empirical equations with high R2 (0.989–0.996) between the responses and independent variables were derived. The optimum conditions for the maximum of BDW (9.95g/l), TC (7.67mg/l) and CX (7.10mg/l) amounts were: d-glucose (25g/l), mannose content (15.12g/l) and Fe3+ concentration (36.77ppm).

Utilization of different crown ethers impregnated polymeric resin for treatment of low level liquid radioactive waste by column chromatography

The main goal of this study was to find a novel impregnated resin as an alternative for the conventional resin (KY-2 and AN-31) used for low and intermediate level liquid radioactive waste treatment. Novel impregnated ion exchangers namely, poly (acrylamide-acrylic acid-acrylonitril)-N,N’-methylenedi-acrylamide-4,4’(5′)di-t-butylbenzo 18 crown 6 [P(AM-AA-AN)-DAM/DtBB18C6], poly (acrylamide-acrylic acid-acrylonitril)-N,N’-methylenediacrylamide-dibenzo 18 crown 6 [P(AM-AA-AN)-DAM/DB18C6], and poly (acrylamide-acrylic acid-acrylonitril)-N,N’-methylenediacrylamide-18 crown 6 [P(AM-AA-AN)-DAM/18C6] were prepared and their removal efficiency of some radionuclides was investigated. Preliminary batch experiments were performed in order to study the influence of the different derivatives of 18 crown 6 on the characteristic removal performance. Separation of 134Cs, 60Co, 65Zn and (152+154)Eu radionuclides from low level liquid radioactive waste was investigated by using column chromatography with P(AM-AA-AN)-DAM/DtBB18C6 and metal salt solutions traced with the corresponding radionuclides. Breakthrough data was obtained in a fixed bed column at room temperature (298 K) using different bed heights and flow rates. The breakthrough capacities were found to be 94.7, 83.3, 58.7, 43.1 (mg/g) for 60Co, 65Zn, 134Cs, and (152+154)Eu, respectively. Pre-concentration and separation of all radionuclides under study have been carried out using different concentration of nitric and/or oxalic acids.

Modeling uranium transport in acidic contaminated groundwater with base addition

This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO 3 −, SO 4 2−, U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

Treatment of a combined dairy and domestic wastewater in an up-flow anaerobic sludge blanket (UASB) reactor followed by activated sludge (AS system)

The feasibility of using an up-flow anaerobic sludge blanket (UASB) reactor followed by activated sludge (AS system) for the treatment of wastewater discharged from dairy factory was explored. The UASB reactor was operated at a hydraulic retention time (HRT) of 24 h and organic loading rates (OLRs) ranging from 1.9 to 4.4 kgCOD/m 3.d. The average total chemical oxygen demand (COD total) and total biological oxygen demand (BOD 5total) concentrations of the UASB reactor effluent were 1385 and 576 mg/l, corresponding to percentage removal of 69% and 79%, respectively. Total suspended solids (TSS) and volatile suspended solids (VSS) removal averaged above 72% and 75%, respectively. Residual phosphorous and oil and grease concentrations of the UASB reactor effluent were 8.2 and 44 mg/l, corresponding to percentage removal values of 63% and 83%, respectively. This good performance could be attributed to the relatively long sludge residence time (SRT = 76 d) imposed to the reactor. Total and faecal coliform counts were reduced in the treated effluent by a value of 1.07 and 0.9 log 10, respectively. The net sludge yield coefficient was found to be 0.2 g VSS per g COD total removed per day, corresponding to 20% of the total influent COD imposed to the UASB reactor. The volatile solids / total solids (VS/TS) ratio of 0.66 of excess sludge revealed its good quality. Preliminary batch experiments of the AS system treating UASB reactor effluent indicated first-order removal kinetics between total organic carbon (TOC) and contact time. The TOC removal reached 80%, resulting in only 47 mg/l in the final effluent at a HRT of 2.0 h. Accordingly, the AS system was operated at a HRT of 2.0 h. The system achieved a substantial reduction of COD total, BOD 5 total, TSS and oil and grease resulting effluent quality with residual values of only 35.0, 7.0, 14.0 and 2.8 mg/l, respectively. The geometric mean of total and faecal coliform counts was reduced by a value of 1.28 and 1.64 log 10, respectively. Based on these results, it is recommended to use of an integrated system consisting of a UASB reactor followed by the AS system for the treatment of a combined dairy and domestic wastewater to produce a good effluent quality complying with the standards for discharge into agricultural drains.

Removal of total phenols from olive-mill wastewater using an agricultural by-product, olive pomace

The purpose of this study was to investigate the sorption of total phenols, which are contained in olive-mill wastewater (OMWW), on solid by-products of olive pomace processing mills. Preliminary batch experiments were conducted using three different types of olive pomace, dried olive pomace (OP-1), dried and solvent extracted olive pomace (OP-2) and dried, solvent extracted and incompletely combusted olive pomace (OP-3). According to the results, OP-3 showed high performance for total phenols sorption and stability. For sorbent concentration of 10 g L −1 and sorbate concentration of 50 mg L −1, more than 40% of initial total phenols concentration was removed. Sorption kinetics was well described by the pseudo-second order rate model ( R 2 > 0.99). Total phenols removal efficiency was improved by increasing sorbent concentration and solution's pH or decreasing particle size of the sorbent material. The Langmuir and Freundlich isotherms sufficiently described OP-3 sorption capacity for the concentration range studied (50–500 mg L −1). Fixed bed sorption experiments showed that lower flow rates and smaller particle size of sorbent resulted in longer column exhaustion time and higher initial removal efficiency. Experiments with thermally or chemically regenerated OP-3 showed that sorption capacity deteriorated after regeneration.

Effective Anaerobic Decolorization of Azo Dye Acid Orange 7 in Continuous Upflow Packed-Bed Reactor Using Biological Activated Carbon System

The anaerobic reduction of azo dye Acid Orange 7 (AO7) was investigated in a continuous upflow packed-bed reactor (UPBR) containing biological activated carbon (BAC). Preliminary batch experiments using graphite proved the catalytic effect of using a solid electron mediator in the reactor. Before the start of continuous experiments, AO7 adsorption studies were done to control adsorption effects on initial decolorization rates. In a continuous UPBR-BAC system, high azo dye conversion rates were achieved during very short space times (τ) up to 99% in 2.0 min. In order to know which are the crucial and most influencing properties of BAC in AO7 reduction, other materialsgraphite and aluminawith different properties were also tested in UPBRs. The results show that both electron-mediating capability and specific surface area of activated carbon contribute to higher reduction rates. Compared to other continuous and biological processes treating azo dyes, UPBR-BAC seems to be a very effective and promising system for anaerobic azo dye degradation.

Effects of initial saturation on properties modification and displacement of tetrachloroethene with aqueous isobutanol

Packed column experiments were conducted to study effects of initial saturation of tetrachloroethene (PCE) in the range of 1.0–14% pore volume (PV) on mobilization and downward migration of the non-aqueous phase liquid (NAPL) product upon contact with aqueous isobutanol (∼ 10 vol.%). This study focused on the consequences of swelling beyond residual saturation. Columns were packed with mixtures of neat PCE, water and glass beads and waterflooded to establish a desired homogeneous residual saturation, and then flooded with aqueous isobutanol under controlled hydraulic conditions. Results showed a critical saturation of approximately 8% PV for these packed column experimental conditions. At low initial PCE saturations (< 8% PV), experimental results showed reduced risk of NAPL-product migration upon contact with aqueous isobutanol. At higher initial PCE saturations (> 8% PV), results showed NAPL-product mobilization and downward migration which was attributed to interfacial tension (IFT) reduction, swelling of the NAPL-product, and reduced density modification. Packed column results were compared with good agreement to theoretical predictions of NAPL-product mobilization using the total trapping number, N T. In addition to the packed column study, preliminary batch experiments were conducted to study the effects of PCE volumetric fraction in the range of 0.5–20% on density, viscosity, and IFT modification as a function of time following contact with aqueous isobutanol (∼ 10 vol.%). Modified NAPL-product fluid properties approached equilibrium within approximately 2 h of contact for density and viscosity. IFT reduction occurred immediately as expected. Measured fluid properties were compared with good agreement to theoretical equilibrium predictions based on UNIQUAC. Overall, this study demonstrates the importance of initial DNAPL saturation, and the associated risk of downward NAPL-product migration, in applying alcohol flooding for remediation of DNAPL contaminated ground water sites.

Facilitated transport of vanadium (V) by supported liquid membranes

A systematic study of the flux of complex vanadium anions through hydrophobic supported liquid membranes is carried out in sulphate media to determine the feasibility of this technique for the removal/recovery of this metal from diluted effluents. Preliminary batch experiments guide us to use mixtures of tertiary amine Alamine 336 and phosphine oxide Cyanex 923 as carrier, dissolved in aromatic diluents. The models previously derived to explain this process in transition state have proven not to be valid for this system due to the slow stripping kinetics of the process and the complex mechanism of the extraction process. Values for the permeability of vanadium in these conditions were obtained in order to have a basis for comparison with other metals. An empirical fit of these data is obtained, which can serve us as a first approach in the design of continuous processes for the recovery of this metal with supported membranes.

Studies on the kinetics of carbon dioxide absorption with immobilised amines (IA)

An interesting innovative concept for the removal of CO2 from sour gas using immobilised amines (IA) in the CO2 absorption process with methyldiethanolamine (MDEA) has been evaluated in our previous work [2]. The positive effect of IA on the absorption behaviour has been demonstrated by means of preliminary batch experiments in an aerated stirred tank reactor. In order to identify the rate-limiting steps in the three-phase system, experiments with a liquid medium in a fixed-bed reactor have been carried out to establish the absorption kinetics of dissolved CO2 onto IA and the desorption (regeneration) kinetics of CO2-loaded IA with MDEA solution. The breakthrough profiles of CO2 at the outlet of the reactor are measured using a newly developed analytical method. Based on the experimentally determined adsorption and packing parameters, a mathematical model has been developed to describe the experiments and found to yield an accurate prediction of the dynamic CO2 concentration profiles. It could be shown experimentally that the adsorption rate of dissolved CO2 with IA (kliquid–solid = 1.54 × 10−7 m/s, 298 K) and the desorption rate of CO2-loaded IA (ksolid–liquid = 5.64 × 10−8 m/s, 298 K) are the same order of magnitude and both constitute rate-limiting processes. On the basis of observations and results, two possible mechanisms for this novel three-phase gas–liquid–solid system are proposed and compared with one another.

Physico-chemical factors affecting the [formula omitted] removal in a rotating biological contactor (RBC) treating UASB effluent

The removal mechanism of E. coli from UASB effluent using a Rotating Biological Contractor (RBC) has been investigated. Preliminary batch experiments in a RBC indicate a first-order removal kinetics. Variation in the dissolved oxygen concentration and E. coli counts over the depth of the RBC has been recorded and indicates that the RBC is not a completely mixed reactor. Therefore batch experiments were carried out in a beaker where the different operating conditions can be controlled. Factors affecting the removal of E. coli via a biofilm system as stirring, dissolved oxygen concentration, pH, and addition of cationic polymer were investigated. The results obtained indicated that the most important removal mechanism of E. coli in the biofilm is the adsorption process, followed by sedimentation. Die-off is a relatively minor removal mechanism in an RBC system. Higher removal rate of E. coli was observed in an aerobic compared to an anaerobic biofilm system. Variation of dissolved oxygen concentration (3.3–8.7 mg l −1) and pH-values between 6.5 and 9.3 did not exert any significant effect on the removal rate of the E. coli by the heterotrophic biofilm. A rapid adsorption of E. coli to the biofilm occurred during the first days after adding the cationic polymer, after which the adsorption slowed down.

Performance of immobilized moss in the removal of137Cs and90Sr from actual low-level radioactive waste solutions

The efficiency of immobilized moss as a bio-sorbent for the removal of 137Cs and 90Sr radionuclides from actual low-level radioactive waste (LLW) solutions was investigated. Preliminary batch experiments with the moss (Funaria hygrometrica) for the sorption of Cs and Sr have shown a pH dependent binding trend from pH 1–13, with maximum binding between pH 5–10. Time dependence of the batch studies showed that a contact time of 30 minutes was sufficient to reach equilibrium. Column experiments for the sorption of Cs and Sr by moss after immobilizing in polymer silica matrix demonstrated that the sorbent is capable of removing considerable amounts of Cs and Sr from actual LLW solutions under constant flow conditions. The adsorption capacity was estimated to be 8.5 mg/g for Cs and 15 mg/g for Sr. These sorbed metal ions from the column could be leached out using 0.20M nitric acid. The regenerated sorbent exhibited relatively the same initial binding capacity of both Cs and Sr even after 3 cycles of reuse.

Production of different morphologies of biocompatible polymeric materials by supercritical CO(2) antisolvent techniques.

High-value biocompatible-polymers have been processed with supercritical antisolvent techniques to produce solid structures of different shape and size. In particular, a class of hyaluronic acid-derived polymers (Hyaff11-p100, Hyaff11-p80, Hyaff11-p75, Hyaff 302) have been used to obtain various morphologies such as microspheres, threads, fibers, networks, and sponges. The effect of thermodynamic variables on precipitation were highlighted in some preliminary batch experiments. Then, different products were obtained by tuning the values of operating parameters. Threads and fibers were the result of a continuous supercritical antisolvent (SAS) process where a concentrated polymer solution was pumped through a micrometric nozzle: The threads showed a reticular internal structure with an adjustable type of cavity. For production of networks and sponges, the concentration of polymer plays the key role. Below a critical value it was not possible to obtain a continuous network, while above it, a structure similar to that of the natural bone with three types of internal microporosity were obtained. Again, by tuning pressure and polymer concentration, the internal porosity could be controlled. Microparticles were also produced by the SAS process, and a control of their morphology was achieved by varying the concentration of the polymer in the starting solution and the density of organic solvent-CO(2) mixtures. All the products obtained by SAS have negligible content of residual solvent. A qualitative interpretation of experimental results is presented.

The application of dealginated seaweed as a cation exchanger foron-line preconcentration and chemical speciation of trace metals

Methods for the on-line preconcentration of Cd2+, Cr3+, Cu2+ and Pb2+ and chemical speciation of Cr3+ and CrO42− using a microcolumn (50 × 7 mm id) packed with about 0.34 g dealginated seaweed biomass are described. Preliminary batch experiments showed that metal sorption by the biomass is rapid, about 90% of the metals in solution is taken up in less than 5 min, and occurs in a wide pH range, 2–7. Maximum binding was obtained between pH 6 and 7 and the effective binding capacities at pH 6, determined from column breakthrough measurements using a flow rate of 0.8 mL min−1, were 4.0, 8.7, 9.4 and 8.5 µmol g−1 for Cd, Cr Cu and Pb, respectively. Unretained CrO42− was separated from Cr3+ thus making it possible to determine the levels of both species in solution. The analytical procedures developed for metal preconcentration and chromium speciation were validated by analyses of two Lake Ontario water reference materials, TMDA 51.2 and TMDA 54.2, and a synthetic seawater sample. Comparison of the results obtained by the proposed methods with the certified total values using the Student t test at 95% confidence limit showed that the differences were not statistically significant. Independent confirmation of the accuracy of the chromium speciation results was obtained using the measurement of absorbance of the 1,5-diphenylcarbohydrazide–chromium complex, before and after treatment with nitric acid, to determine the levels of CrO42− and Cr3+ by difference. The results obtained with the proposed method for the analyses of TMDA 51.2 and TMDA 54.2 for Cr3+ and CrO42− were 20 ± 0.2 and 39 ± 0.3 µg L−1, and 162 ± 1 and 299 ± 1 µg L−1, compared with 12 ± 5 and 54 ± 31, and 132 ± 12 and 313 ± 16 µg L−1, respectively.