Aqueous Waste Streams Research Articles

Experimental Data and Theoretical (Chemodel Using the Differential Evolution Approach and Linear Solvation Energy Relationship Model) Predictions on Reactive Extraction of Monocarboxylic Acids Using Tri-n-octylamine

The carboxylic acids such as ethanoic, propanoic, and butanoic acids are most widely used in pharmaceutical, agricultural, polymer, and chemical industries. The separation of acids from fermentation broth and aqueous waste stream can be intensified by reactive extraction. The reactive extraction of carboxylic acids (ethanoic, propanoic, and butanoic acids) by N,N-dioctyloctan-1-amine (TOA) with six different diluents [decane, benzene, 4-methyl-2-pentanone (MIBK), decan-1-ol, chloroform, and decane (w = 0.725) + decan-1-ol (w = 0.275)] is studied. The physical equilibria using pure diluents with the same conditions are also studied. Distribution coefficients, loading factors, and degree of extraction are calculated as a result of batch extraction experiments. In the present work, a population-based search algorithm, differential evolution (DE), is employed as an optimization routine to estimate the optimum values of equilibrium constants (KE) and stoichiometries of reactive extraction (m:n) through propose...

Encapsulation of caesium-loaded Ionsiv in cement

The microporous material Ionsiv is used for 137Cs removal from aqueous nuclear waste streams. In the UK, Cs-loaded Ionsiv is classed as an intermediate-level waste; no sentencing and disposal route is yet defined for this material and it is currently held in safe interim storage on several nuclear sites. In this study, the suitability of fly ash and blast furnace slag blended cements for encapsulation of Cs-Ionsiv in a monolithic wasteform was investigated. No evidence of reaction or dissolution of the Cs-Ionsiv in the cementitious environment was found by scanning electron microscopy and X-ray diffraction. However, a small fraction (≤ 1.6 wt.%) of the Cs inventory was released from the encapsulated Ionsiv during leaching experiments carried out on hydrated samples. Furthermore, it was evident that K and Na present in the cementitious pore water exchanged with Cs and H in the Ionsiv. Therefore, cement systems lower in K and Na, such as slag based cements, showed lower Cs release than the fly ash based cements.

Synthesis and characterisation of mesoporous silica phases containing heteroatoms, and their cation exchange properties. Part 4. Measurement of distribution coefficients for 241-Am, 51-Cr, 59-Fe, 54-Mn, 63-Ni, 236-Pu and 65-Zn

Previous papers in this series have described the synthesis and characterisation of a series of MCM-41 phases of differing pore structure and framework compositions [1], isotherm studies designed to illustrate their cation selectivity [2], and their efficiency in scavenging 137-Cs, 89-Sr and 57-Co from various solutions [3] appropriate to the potential remediation of aqueous nuclear waste streams. This work extends the radioisotope studies to include, 241-Am, 236-Pu for their importance in the treatment of spent nuclear fuel (241-Am also has a wide use in smoke detectors) and 51-Cr, 59-Fe, 54-Mn, 65-Zn which are present in nuclear wastes from neutron activation in nuclear installations, as well as those arising from medical uses. Measurement of distribution coefficients enabled the construction of selectivity series which demonstrated the versatility of the phases for scavenging specific isotopes.

Perfluoroalkyl sulfonic and carboxylic acids: A critical review of physicochemical properties, levels and patterns in waters and wastewaters, and treatment methods

Perfluorinated acids (PFAs) are an emerging class of environmental contaminants present in various environmental and biological matrices. Two major PFA subclasses are the perfluorinated sulfonic acids (PFSAs) and carboxylic acids (PFCAs). The physicochemical properties and partitioning behavior for the linear PFA members are poorly understood and widely debated. Even less is known about the numerous branched congeners with varying perfluoroalkyl chain lengths, leading to confounding issues around attempts to constrain the properties of PFAs. Current computational methods are not adequate for reliable multimedia modeling efforts and risk assessments. These compounds are widely present in surface, ground, marine, and drinking waters at concentrations that vary from pg L− 1 to μg L− 1. Concentration gradients of up to several orders of magnitude are observed in all types of aquatic systems and reflect proximity to known industrial sources concentrated near populated regions. Some wastewaters contain PFAs at mg L− 1 to low g L− 1 levels, or up to 10 orders of magnitude higher than present in more pristine receiving waters. With the exception of trifluoroacetic acid, which is thought to have both significant natural and anthropogenic sources, all PFSAs and PFCAs are believed to arise from human activities. Filtration and sorption technologies offer the most promising existing removal methods for PFAs in aqueous waste streams, although sonochemical approaches hold promise. Additional studies need to be conducted to better define opportunities from evaporative, extractive, thermal, advanced oxidative, direct and catalyzed photochemical, reductive, and biodegradation methods. Most PFA treatment methods exhibit slow kinetic profiles, hindering their direct application in conventional low hydraulic residence time systems.

Highly Efficient Asymmetric Synthesis of Sitagliptin

A highly efficient synthesis of sitagliptin, a potent and selective DPP-4 inhibitor for the treatment of type 2 diabetes mellitus (T2DM), has been developed. The key dehydrositagliptin intermediate 9 is prepared in three steps in one pot and directly isolated in 82% yield and >99.6 wt % purity. Highly enantioselective hydrogenation of dehydrositagliptin 9, with as low as 0.15 mol % of Rh(I)/(t)Bu JOSIPHOS, affords sitagliptin, which is finally isolated as its phosphate salt with nearly perfect optical and chemical purity. This environmentally friendly, 'green' synthesis significantly reduces the total waste generated per kilogram of sitagliptin produced in comparison with the first-generation route and completely eliminates aqueous waste streams. The efficiency of this cost-effective process, which has been implemented on manufacturing scale, results in up to 65% overall isolated yield.

Removal of Common Organic Solvents from Aqueous Waste Streams via Supercritical CO2 Extraction: A Potential Green Approach to Sustainable Waste Management in the Pharmaceutical Industry

Supercritical CO2 extraction of aqueous streams is a convenient and effective method to remove commonly used solvents of varying polarities from aqueous waste streams. The resulting aqueous layers can potentially be sewered; whereas the organic layer can be recovered for potential reuse. Supercritical fluid extraction (SFE) is a technology that is increasingly being used in commercial processes (1). Supercritical fluids are well suited for extraction of a variety of media, including solids, natural products, and liquid products. Many supercritical fluids have low critical temperatures, allowing for extractions to be done at modestly low temperatures, thus avoiding any potential thermal decomposition of the solutes under study (2). Furthermore, the CO2 solvent strength is easily tuned by adjusting the density of the supercritical fluid (The density is proportional to the pressure of the extraction process). Since many supercritical fluids are gases at ambient temperature, the extract can be concentrated by simply venting the reaction mixture to a cyclone collection vessel, using appropriate safety protocols.

Studies on a synthetic sitinakite-type silicotitanate cation exchanger. Part 2. Effect of alkaline earth and alkali metals on the uptake of Cs and Sr radioisotopes

A commercially available synthetic silicotitanate (IONSIV ® IE-911), with a sitinakite-like structure, is a candidate material for the remediation of aqueous nuclear waste streams. These streams often vary in both cation composition and cation concentration. Commonly Na, K, Mg, Ca and Ba are present, and sodium is the most prevalent with barium present at much lower concentrations. Batch experiments to measure distribution coefficients (K d) have been carried out to monitor the effect of these cations on the removal of the fission products Cs and Sr from simulated aqueous waste streams relevant to their remediation prior to release to the environment.

Effect of binary extractants and modifier–diluents systems on equilbria of propionic acid extraction

Propionic acid is an important carboxylic acid widely used in chemical industries. The recovery from aqueous waste streams and fermentation broth is of research interest. Extraction of carboxylic acids by reactive extraction using extractant-diluent, mixed extractants in diluents and extractants in mixed diluents etc. are emerging areas of study. With this aim reactive extraction of propionic acid was carried out to study: (i) effect of binary extractants (tri-n-octylamine(TOA):tri-n-butylphosphate (TBP), TOA:Aliquat 336 and TBP:Aliquat 336), (ii) effect of modifier (1-decanol) in different diluents (kerosene, n-octane, n-heptane, petroleum ether, butyl acetate, MIBK, 2-octanol, dodecanol, hexane) and (iii) effect of phase volume. Improved extractions using binary extractants and binary diluents were observed. Since liquid–liquid extraction is dependent on effect of modifier concentration, effect of phase volume, presence of single or binary extractants and binary diluents, the study will be useful in the design of reactive extraction process for propionic acid recovery.

Studies on a synthetic sitinakite-type silicotitanate cation exchanger: Part 1: Measurement of cation exchange diffusion coefficients

A commercially available synthetic silicotitanate (IONSIV ® IE-911), with a sitinakite-like structure, is a candidate material for the remediation of aqueous nuclear waste streams. These streams are often complex in their cation composition. This work investigates the effect of the presence of Na, K, Mg, Ca and Ba on the rates of removal of Cs and Sr radioisotopes as cations of importance in aqueous nuclear waste streams. Results are compiled as isotopic diffusion coefficients, and by analysis of changes in pH with time, observed as the systems reach equilibrium. This kinetic treatment provides necessary data for use in the modelling of plant performance and for the accurate determination of distribution coefficients which will be the subject of the second part in this series.

Surfactant Solubilization and the Direct Encapsulation of Interfacially Active Phenols in Mesoporous Silicas

The solubilization of phenols in micelles of cetyltrimethyl ammonium bromide leads to microstructural changes from spherical micelles to wormlike micelles and then to vesicles. These microstructures are then used to template silicas. There is a transition from highly ordered hexagonal mesoporous silicas of the M41S family to lamellar structures, as the phenolic dopant concentration is increased. The results have implication to the removal of phenols from aqueous waste streams through the micellar enhanced ultrafiltration process. The entrapment of phenols in mesoporous silicas provides a way to sequester such contaminants in concentrated form.

Role of Thermochemical Conversion in Livestock Waste-to-Energy Treatments: Obstacles and Opportunities

Integrating thermochemical conversion (TCC) technologies with current animal waste treatment practices can treat and reduce quantities of manure from consolidated animal feeding operations. Additionally, TCC technologies can produce value-added, renewable energy products. These products can meet heating and power needs or be catalytically converted into liquid fuels. The primary objectives of this study were to assess opportunities and obstacles in the treatment and energy conversion using currently available TCC processes. Both dry and wet livestock manures were assessed. Dry wastes like poultry litter and feedlot manures can be processed directly via pyrolysis and air/steam gasification technology. The solids in the aqueous waste streams from dairy and swine operations can undergo wet gasification or direct liquefaction processes. Alternatively, these solids can be separated and dried before conversion. Due to high ash and sulfur contents, pretreatment of manure is necessary to prevent catalyst poisoning and promote effective unit operation. While the energy input requirements for a conceptual wet gasification manure treatment system of a model swine farm is larger than a traditional anaerobic digestion operation, there are many significant advantages in implementing TCC technology including the following: compact design; faster treatment times; reduction of odors, BOD, and pharmaceutically activated compounds; and elimination of sludge.

Novel low density granular adsorbents – Properties of a composite matrix from zeolitisation of vermiculite

This paper reports the preparation and properties of a new low density granular absorbent material based on a zeolite/vermiculite composite. The composite prepared addresses a number of important issues relating to the use of zeolites in environmental and waste management applications. The material prepared has large particle size due to binderless adhesion of zeolite crystals within the protective lamellar matrix provided by the vermiculite granule. Additionally, the porous nature of new material ensures that it outperforms natural zeolite grains in ion-exchange tests. The material was shown to have a low bulk density (0.75 g cm(-3)) adding the benefit that the majority of grains float on water for over 15 h. The conclusion of the study is that the use of composite matrices enable the preparation of materials which show the physical properties of the host, (e.g., granular and low density), whilst maintaining the powder-like properties (e.g., high ion-exchange and small crystal size) of the active component. The resulting material can be easily handled and separated from aqueous waste streams using either flotation or exploiting its granular nature.

Development of an Integrated Enzymatic Treatment System for Phenolic Waste Streams

An integrated enzymatic treatment system, which includes Coprinus cinereus peroxidase (CIP) production, processing, and usage in batch or plug flow reactors, is being developed to remove phenolic compounds from the aqueous waste streams. CIP production at bench scale yielded a maximum growth medium activity of approximately 60 U CIP ml−1. A CIP enzyme solution was prepared for use in treatment by successive filtration steps. This yielded a 4.5-fold increase in enzyme activity, with 87% enzyme activity recovery, and 83% reduction in the solution's Chemical Oxygen Demand. The purity of CIP was observed to have no effect on the ability of the enzyme to remove phenol from the aqueous solutions within the range of enzyme solution purities tested. Contrary to observations reported for phenol removal from buffered solutions, the addition of polyethylene glycol to non-buffered reaction solutions had no positive effect on the phenol removal accomplished at pH 7 in these experiments. The efficiency of enzyme use in a plug flow reactor was improved by step additions of CIP and H2O2.

High-Power Pulsed Corona for Treatment of Pollutants in Heterogeneous Media

A technical overview of a European project on pulsed corona (PC) treatment of polluted streams is presented. Versatile high-power systems that are capable of cleaning both aqueous and gaseous streams in heterogeneous media, in either a corona above water reactor or an aerosol reactor, have been developed. Both reactors are capable of high-phenol removal yields from aqueous streams and increase the biochemical oxygen demand/chemical oxygen demand ratio for several nonbiodegradable wastewaters to such degree that further biodegradation becomes possible. The PC combined with a catalyst is capable of cleaning gaseous streams that are polluted by toluene, styrene, and malodorous constituents. Reduction rates of toluene that are higher than 99% have been achieved, and very high odor-removal efficiency has been demonstrated. The reliable operation of high-power all-solid-state compact nanosecond pulsers has also been demonstrated. For the second phase of the project, a high-power pulser was designed. One compression stage suffices for the formation of 60-kV 3-J pulses across a reactor that has a discharge impedance of approximately 100 Omega at a pulse repetition frequency of up to 500 Hz; the rise time is 15 ns, and the duration is 100 ns. The system scale-up is also analyzed. The estimated price of water treatment in systems that were scaled up to 50 m3 /h is 2 euro/m3. Incineration of aqueous organic waste streams can cost 500 euro/m3 or more, depending on the nature of the contamination, so the PC water-treatment technology may become highly competitive. It is planned in the future to investigate the cleaning efficiency of the developed processes with different industrial wastes, both at laboratory conditions and in the field

Experimental Measurement of Proton, Cd, Pb, Sr, and Zn Adsorption Onto the Fungal Species Saccharomyces Cerevisiae

Proton, Cd, Pb, Sr, and Zn adsorption onto the fungal species Saccharomyces cerevisiae were measured in bulk adsorption experiments as a function of time, pH, surface: metal ratio, and ionic strength, and we measured the electrophoretic mobility of the cells as a function of pH. We modeled the acid/base properties of the fungal cell wall by invoking a nonelectrostatic surface complexation model with four discrete surface organic acid functional group types, with average pKa values (with 1 sigma uncertainties) of 3.4 +/- 0.4, 5.0 +/- 0.2, 6.8 +/- 0.4, and 8.9 +/- 0.6. The affinity of the fungal cells for the metal ions follows the following trend: Pb > Zn > Cd > Sr. We used the metal adsorption data to determine site-specific stability constants for the important metal fungal surface complexes. Our results suggest that S. cerevisiae may represent a novel biosorbent for the removal of heavy metal cations from aqueous waste streams.

Kinetics and Mechanism of Wet Air Oxidation of Butyric Acid

Low molecular weight acids are common intermediate reaction compounds formed during the wet air oxidation (WAO) of aqueous waste streams, and frequently their oxidation is the rate-controlling step in the overall reaction. The WAO kinetics of aqueous solutions of butyric acid was studied in a stainless steel 316 autoclave over a temperature range of 200−320 °C with a total pressure of 15 MPa of synthetic air, which provides an excess of oxygen. Kinetic models were developed with respect to various concentrations of butyric acid and chemical oxygen demand (COD). Oxidation reactions always obeyed a pseudo-first-order kinetic, but two different activation energies were needed to represent the temperature dependence in two ranges, namely 200−275 and 275−320 °C. This finding can be explained by the competition between two main reaction pathways in the oxidation of the acid, since both pathways take place simultaneously. A mechanism in accordance with the results obtained is proposed.

A Liquid-Phase Precipitation Process for Selective Removal of Critical Inorganic Species from the Hanford Waste Streams

A liquid-phase precipitation (LPP) process was evaluated in a bench-scale setup for selective removal of radioactive species as well as key nonradioactive species from DOE aqueous waste streams. The DOE Hanford supernatant Tank stream (101-SY) in a simulated inactive form was employed for process evaluation. A developed solid–liquid equilibrium (SLE) thermodynamic framework with two predictive equations was used to model the experimental data. The preliminary data reveal that the LPP process is effective in separating: (1) alkaline cations (e.g., calcium, strontium, and likely barium) from their acidic and alkaline aqueous streams, (2) aluminum from acidic aqueous streams, and (3) phosphate and fluoride from both acidic and alkaline aqueous streams. The process is substantially less effective in separating alkali cations, including cesium, from aqueous streams. The sulfate concentration in the tested 101-SY stream was low (456 mg/L), which precludes drawing a conclusion regarding the effectiveness of the LPP process in removing sulfate. The technical feasibility and possible applicability of the LPP process across the DOE complex in treating different types of wastes (acidic-dissolved sludge, acidified supernatant, alkaline- dissolved sludge, and alkaline supernatant) were discussed.

Fluorotelomer Alcohol BiodegradationDirect Evidence that Perfluorinated Carbon Chains Breakdown

There is increasing scientific interest to understand the environmental fate of fluorotelomer alcohols (FTOHs) and fluorotelomer-based products which may break down to FTOHs. Both are expected to enter aqueous waste streams, which would be processed in a wastewater treatment plant and therein subject to microbial biodegradation. We investigated the biodegradation of 3-14C, 1H,1H,2H,2H-perfluorodecanol [CF3(CF2)6(14)CF2CH2CH2OH, 14C-8-2 FTOH] in mixed bacterial culture and activated sludge. 14CO2 and 14C-organic volatiles in the headspace of the sealed bottles and bottles with continuous air flow were analyzed up to 4 months. After sample extraction with acetonitrile, 14C-labeled biotransformation products (metabolites) were quantified by LC/ARC (on-line liquid chromatography/ accurate radioisotope counting) and identified by quadrupole time-of-flight (Q-TOF) mass spectrometry and GC/MSD (mass selective detector). Three metabolites not yet reported in the literature have been identified as CF3(CF2)6(14)CHOHCH3 (7-2 sFTOH), CF3(CF2)6(14)CH=CHCOOH (7-3 unsaturated acid or 7-3 u acid), and CF3(CF2)6(14)CH=CHCONH2 (7-3 u amide) along with five previously reported metabolites [CF3(CF2)6(14)CF2CH2CHO (8-2 FTAL), CF3(CF2)6 (14)CF2CH2COOH (8-2 acid), CF3(CF2)6(14)CF=CHCOOH (8-2 u acid), CF3(CF2)6(14)CH2CH2COOH (7-3 acid), and CF3(CF2)6(14)COOH (PFOA)]. No CF3(CF2)6(14)CF2COOH (14C-PFNA) was observed, indicating that alpha-oxidation does not take place. It was found that strong adsorption to the activated sludge and subsequent transformation, even under continuous air flow, greatly reduced partitioning of 8-2 FTOH or any transformation products to air. CF3(CF2)4COOH (PFHA; perfluorohexanoic acid) was observed and increased in mixed bacterial culture over 28 days and accounted for about 1% of the initial 14C-8-2 FTOH concentration from day 28 to day 90. 14CO2 accounted for 1% of initial 14C in activated sludge with continuous air flow at day 1 and increased over time. In closed bottles, 14CO2 in the headspace of activated sludge medium increased to 12% of the available 14C over 135 days with periodic addition of ethanol, as compared to 3% when no additional ethanol was added. These results show that replenishment of organic carbon enhanced microbial mineralization of multiple--CF2--groups in the fluorocarbon chain of 14C-8-2 FTOH. At day 90 the net increase of fluoride ion in the mixed bacterial culture was 93 microg L(-1), equivalent to 12% of total mineralization (destruction) of the 14C-8-2 FTOH. These results demonstrate that perfluorinated carbon bonds of 14C-8-2 FTOH are defluorinated and mineralized by microorganisms under conditions which may occur in a wastewater treatment plant, forming shorter fluorinated carbon metabolites.

Evaluation of Cyanex 923-coated magnetic particles for the extraction and separation of lanthanides and actinides from nuclear waste streams

In the magnetically assisted chemical separation (MACS) process, tiny ferromagnetic particles coated with solvent extractant are used to selectively separate radionuclides and hazardous metals from aqueous waste streams. The contaminant-loaded particles are then recovered from the waste solutions using a magnetic field. The contaminants attached to the magnetic particles are subsequently removed using a small volume of stripping agent. In the present study, Cyanex 923 (trialkylphosphine oxide) coated magnetic particles (cross-linked polyacrylamide and acrylic acid entrapping charcoal and iron oxide, 1:1:1, particle size=1–60 μm) are being evaluated for the possible application in the extraction and separation of lanthanides and actinides from nuclear waste streams. The uptake behaviour of Th(IV), U(VI), Am(III) and Eu(III) from nitric acid solutions was investigated by batch studies. The effects of sorption kinetics, extractant and nitric acid concentrations on the uptake behaviour of metal ions were systematically studied. The influence of fission products (Cs(I), Sr(II)) and interfering ions including Fe(III), Cr(VI), Mg(II), Mn(II), and Al(III) were investigated. The recycling capacity of the extractant-coated magnetic particles was also evaluated.

Trimethylsilyl Trifluoromethanesulfonate Catalyzed One-Pot Method for the Conversion of Aldehydes to Homoallyl Ethers in an Ionic Liquid

A mild method for the trimethylsilyl trifluoromethanesulfonate (TMSOTf) catalyzed one-pot synthesis of homoallyl ethers from aldehydes has been developed in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim] [OTf]). The advantages of this method include the use of a recyclable ionic liquid, facile product isolation without employing excess organic solvent, elimination of an aqueous waste stream, and mild reaction conditions.