Caustic Addition Research Articles

In-situ oxygen generation using Titanium foam/IrO2 electrode for efficient sulfide control in sewers

Hydrogen sulfide (H2S) causes corrosion of pipeline network and endangers sewer’s normal operation, while the rehabilitation or replacement of sewer network incurs expensive manpower and material costs. Conventional chemical dosing strategies such as oxygen injection and caustic soda addition, confront issues with transport and storage of chemical reagents as well as dose control. In contrast, electrochemical treatment techniques have evoked growing attention in sewer management due to its capacity of in-situ effective agent production, real-time dose control and amenability to automation. In this study, the performances of anodic oxygen production using Ti/IrO2 and Titanium foam/IrO2 as electrodes were investigated. Titanium foam/IrO2 electrode exhibited the superior oxygen evolution capacity, with the dissolved oxygen (DO) level attained in the range 8–9 mg L-1 (i.e., higher than that of 5–6 mg L-1 by Ti/IrO2 electrode). It was also indicated that a decrease in flow rate or an increase in current density would accelerate its in-situ oxygen production. DO production with the presence of COD, NH4+, HCO3−, H2PO4−/HPO42− was approximately 6.78–8.37 mg L-1. Moreover, this electrochemical method was illustrated to successfully achieve sulfide removal efficiency of 90 % in the simulated sewage experiment. The cathode compartment simultaneously produced caustic soda (∼0.4 wt% in 210 min), thereby contributing to further sulfide removal. Additionally, the effect of real sewage with different conductivities on sulfide removal proved the wide applicability of electrochemical technology in sewer management. Overall, this study demonstrated the practical potential of concurrent in-situ anodic oxygen production and cathodic caustic soda generation for sulfide control in sewers.

Simultaneous production and recovery of volatile fatty acids from fermentation process using an electrochemically assisted up-flow granular sludge bed reactor

A continuous production and in-line recovery of volatile fatty acids (VFAs) was developed by coupling an electrochemical cell (EC) to the recycling line of an up-flow anaerobic sludge bed (UASB) reactor. The use of an easy fermentable feedstock (glucose) was proposed for a fast production of VFAs. The EC allowed the simultaneous recovery of VFAs while producing alkali equivalent and hydrogen brought to the reactor, allowing to decrease caustic addition and promoting VFA production. Duplicate systems were used with glucose at an initial concentration of 15 g/L for Phases I to III, and increased to 60 g/L in a stepwise manner during Phase IV to VI. The EC was connected using 3.5 V to the UASB reactor at Phase III (15 g/L glucose, hydraulic retention time (HRT): 24 h), decreasing by 46 % the VFA concentration in the reactor mixed liquor and the sodium hydroxide consumption by 49 %. The highest VFA concentration in the anode chamber was 4.6 times higher than in the reactor. The highest caproic acid production achieved corresponded to 6.01 g/L during Phase IV (30 g/L glucose, HRT: 24 h). At the end of the trial, the voltage was increased up to 6.0 V and the water addition in the anode chamber was stopped to build up the VFA concentration, reaching 27.80 and 28.05 g/L for EC1 and EC2, respectively. The coupled UASB-EC system showed promising results in terms of good recovery of the VFAs from the fermentation broth, decrease of the alkali demand and caproic acid production.

Corrosion Rate of Carbon Steel A106 Gr B in Amine-CO2 Contained Solutions

Carbon dioxide (CO2) is one of the corrosive element which exists in oil and gas industries. To prevent CO2 corrosion on carbon steel pipelines, amine-base solvent and caustic solutions are commonly applied. Accordingly, effectiveness of amine base solvent and caustic solutions to reduce risk of corrosion becomes key parameters in determining service lifetime of pipelines made of carbon steel. In this research, the corrosion rate of carbon steel A106 Gr B in amine solutions combined with saturated CO2 gas and caustic solution was studied. The experiments were carried out in static conditions and the Linear Polarization Resistance (LPR) technique was used to measure the corrosion rate (as per ASTM G 5-94). It was found that the corrosion rate in the amine-based solution had shown remarkable results. Somehow, the corrosion rate in an amine-based solvent containing saturated CO2 gas has increased to 200%. The temperature increment to 50°C from room temperature has also increased the corrosion rate. Meanwhile, the caustic addition in amine solution has reduced the corrosion rate of carbon steel.

The Performance of Iraqi Bentonite Using Soda Ash and Caustic Soda Additives

Choosing an adequate drilling fluid is of paramount importance in drilling operations. Thus, controlling the drilling fluid properties is by means of the appropriate selection of drilling fluid components of base fluids, solids, and additives to preserve drilling fluid properties. The aim of this study is to use the available and low cost Iraq's mineral resources. One of these minerals is presented by the Iraqi calcium montmorillonite clay (Ca-bentonite) was obtained from Wadi Bashera / Western Desert /Anbar Governorate to be used as an alternative active solid instead of spending hard currency on importing commercial clay. This study was grouped into two workflows. In the first workflow, XRF and XRD analyzes were performed after grinding the Iraqi raw bentonite rocks and screening it to separate the impurities in order to find out the chemical composition (oxides) and mineral composition (clay and non-clay minerals). The XRF analysis showed that Iraqi bentonite has Al2O3 to SiO2 ratio of 0.3623 which is approximately similar to 0.3455 that obtained by Wyoming bentonite. The XRD analysis detected that Iraqi bentonite is mainly composed of montmorillonite and palygorskite which form the predominant constituents of clay minerals, whereas quartz and gypsum are presented as non-clay minerals. The experimental work is the second work flow of this study in which the rheological and filtration properties, in addition pH value and stability of 3wt. % of Iraqi bentonite fresh water based fluid were tested. Two types of additives with different concentrations were used, soda ash and caustic soda. The results of the experimental work showed that, adding different concentrations of soda ash resulted in an increase in the rheological properties of 3wt. % Iraqi bentonite fresh water based drilling fluid. Soda ash within the range of 0.35 to 0.57g /350 cc water (0.35 to 0.57 lb/bbl) can be used to upgrade Iraqi bentonite. Caustic soda addition within range 0.2 to 0.4 g/350 cc water (0.2- 0.4 lb/bbl) caused an increase in the rheological properties of fresh water based drilling fluid prepared with 3 wt. % of Iraqi bentonite. Combination of soda ash and caustic soda with different concentrations revealed better results than that obtained from each additive alone. An improvement in the filtration properties has been also achieved by adding soda ash and caustic soda into the drilling fluid. Also, an enhancement was achieved in stability from 65 % to 98 % with soda ash and caustic soda additions. This study presents an efficient and cost-effective local bentonite for meeting the required drilling fluid rheological properties.

Pilot evaluation of an aqueous/nonaqueous hybrid bitumen extraction process for mineable oil sands

An aqueous/nonaqueous hybrid bitumen extraction (HBE) process for mined oil sand has the potential to reduce thermal energy demand and greenhouse gas emissions while integrating the productivity and robustness of the current commercial process. The process involves the application of a small amount of solvent to pre-soak the mined ore prior to slurry conditioning, followed by the currently used water-based process, albeit at a lower temperature (e.g. 20 °C) and with no need for caustic addition. In this work, the HBE technology is advanced to the testing of a pilot continuous flow system of 100 kg per hour. This communication describes the extraction outcomes of a series of pilot HBE flotation tests conducted at various extraction conditions, and determination of the respective residual solvent contents in the extraction tailings. Results showed that bitumen recoveries and froth qualities from the pilot HBE process depended on the type and dosage of solvent used to soak the ore prior to slurry conditioning, as well as on the slurry conditioning and residence time. Importantly, lower-temperature HBE could produce comparable or higher bitumen recoveries than those achieved using standard Clark hot water extraction; bitumen froth generated from ambient HBE contained lower fines or water contents. The amount of residual solvent in the tailings produced from the pilot hybrid extractions largely correlated to the unrecovered bitumen percentage. For good-processing ores, for which over 90% bitumen recoveries were achieved, the amount of solvent lost to the tailings was below the regulatory limit even without the use of a tailings solvent recovery unit.

Waterless bleaching of knitted cotton fabric using supercritical carbon dioxide fluid technology

Cotton fiber is the most widely produced and utilized natural fiber with a popular usage in our planet. A substantial amount of clean water is utilized during conventional cotton fiber pretreatment. In this study, we investigated the bleaching possibility of knitted cotton fabric by using supercritical carbon dioxide as a medium, as a cleaner waterless alternative, at pressures in the range of 180 and 250 bar and at temperatures ranging from 80 °C (at the pressure of 180 bar with 505 kg/m3) to 120 °C (at the pressure of 250 bar with 539 kg/m3) for 20 min with either solely hydrogen peroxide usage at 5% and 15% concentrations or combination usage of hydrogen peroxide with necessary related auxiliaries such as peroxide stabilizer at 1% and 8% concentrations and caustic soda at 3% concentration in comparison with conventional aqueous hydrogen peroxide bleaching process in order to support environmentally friendly, sustainable textile production leading to more sustainable future for our planet. Also, the effects of different washing types as after-treatment process following waterless and aqueous peroxide bleaching processes on the whiteness performance of cotton fabrics were also explored. Whiteness properties, moisture management performances, oxycellulose formation and FTIR (ATR) spectra of cotton fabrics bleached in aqueous and waterless supercritical carbon dioxide (scCO2) medium were determined and compared. In waterless scCO2 media, bleaching at 80 °C resulted in higher whiteness improvement than bleaching at 120 °C leading to whiter appearance. Bleaching of cotton cellulosic fiber at 80 °C for 20 min in scCO2 media displayed better whiteness results than conventional water based bleaching at 80 °C. The inclusion of caustic soda in waterless scCO2 hydrogen peroxide bleaching process resulted in significant decline on whiteness level of cotton for both 80 °C and 120 °C bleaching temperatures. When the aqueous conventional bleaching process and the anhydrous (waterless supercritical carbon dioxide fluid) bleaching process compared in the case of solely hydrogen peroxide usage at both 80 °C and 120 °C, waterless supercritical carbon dioxide fluid bleaching process (whether or not after-treated following the bleaching process) resulted in higher whiteness values leading to whiter appearance. Bleaching process with solely 5% and 15% hydrogen peroxide involvement in waterless supercritical carbon dioxide media at 80 °C for only 20 min and without any aqueous after clearing treatment led to approximately 30% and 51% whiteness improvement on cellulosic cotton fiber knitted fabric, respectively. There was no moisture management improvement trend due to caustic soda addition into peroxide bleaching process in waterless scCO2 media. The addition of after-treatment process (catalase enzyme treatment in water at 50 °C and then washed with water at 87 °C in company with wetting agent and rinsing in cold water) following peroxide bleaching in scCO2 media improved the moisture management properties of bleached cotton fabric. Although the bleaching process performed in scCO2 medium resulted in a higher oxidative activity than bleaching process performed in aqueous medium from the measured color yield values of oxycellulose formation evaluation, the consistency of the FTIR (ATR) spectra of the greige, hydrogen peroxide bleached in aqueous and waterless scCO2 media and bleached then after-treated cotton knitted fabrics displays that the respective bleaching process types in both aqueous and waterless scCO2 media had no drastic significant detrimental effect on the surface morphology of the cotton fiber. Consequently, successful waterless hydrogen peroxide bleaching can be carried out for cellulosic cotton fiber knitted fabric in supercritical carbon dioxide media.

Role of mineral flotation technology in improving bitumen extraction from mined Athabasca oil sands: I. Flotation chemistry of water‐based oil sand extraction

AbstractThe role of surface hydrophobicity in water‐based oil sand extraction is examined from the perspective of mineral flotation separation. Although anionic carboxylates (sulphonates) released from bitumen are helpful for charging bitumen and liberating bitumen from sand grains, their presence in oil sand slurries tends to make bitumen and bubbles less hydrophobic. In addition, solid hydrophobization under oil sand extraction conditions can occur through different mechanisms of carboxylate adsorption. It is the hydrophobized fine solids that present challenges for achieving a high bitumen recovery with a good froth quality, due to their competition with bitumen for attachment to bubbles. While chemisorption of carboxylates contributes to hydrophobization of heavy minerals present in oil sands, carboxylate adsorption activated by hydrolyzed metal cations alters silica and clays from hydrophilic to hydrophobic. Different adsorption mechanisms of calcium on silica, clays, and other minerals are analyzed to explain why fine solids of varying mineralogy in combination with calcium affect bitumen extraction differently. Metal ions that activate solid hydrophobization under oil sand extraction conditions are identified from dynamic attachment of solids from mature fine tailings (MFT) to bitumen. To mitigate the effect of fines on oil sand extraction, selective flocculation of fine solids is recognized as especially feasible for bitumen flotation recovery from oil sand middling streams. Future research in reducing or eliminating caustic addition, understanding the role of inorganic anions, and searching for feasible techniques for treating MFT based on different mineralogy and surface properties, are briefly discussed.

Electrochemical Ammonia Recovery from Source-Separated Urine for Microbial Protein Production.

Conventional plant and meat protein production have low nitrogen usage efficiencies and high energy needs. Microbial protein (MP) is an alternative that offers higher nitrogen conversion efficiencies with low energy needs if nitrogen is recovered from a concentrated waste source such as source-separated urine. An electrochemical cell (EC) was optimized for ammonia recovery as NH3/H2 gas mixtures usable for MP production. Undiluted hydrolyzed urine was fed to the caustic-generating cathode compartment for ammonia stripping with redirection to the anode compartment for additional ammonium extraction. Using synthetic urine at 48 A m-2 the nitrogen removal efficiency reached 91.6 ± 2.1%. Tests with real urine at 20 A m-2, achieved 87.1 ± 6.0% and 68.4 ± 14.6% requiring 5.8 and 13.9 kWh kg N-1 recovered, via absorption in acid or MP medium, respectively. Energy savings through accompanying electrolytic H2 and O2 production were accounted for. Subsequently, MP was grown in fed-batch on MP medium with conventional NH4+ or urine-derived NH3 yielding 3.74 ± 1.79 and 4.44 ± 1.59 g CDW L-1, respectively. Dissolution of gaseous NH3 in MP medium maintained neutral pH in the MP reactor preventing caustic addition and thus salt accumulation. Urine-nitrogen could thus be valorized as MP via electrochemical ammonia recovery.

Simultaneous use of caustic and oxygen for efficient sulfide control in sewers

Periodic caustic shock-loading is a commonly used method for sulfide control in sewers. Caustic shock-loading relies on the elevation of the sewage pH to ≥10.5 for several hours, thereby removing sewer pipe biofilms as well as deactivating SRB activity in the remaining biofilm. Although a widely used method, SRB activity is often not completely inhibited, and as such sulfide is still being generated. Here, we propose and experimentally demonstrate an innovative approach which combines caustic with oxygen, another commonly used method, as a dosing strategy for overcoming the drawbacks of caustic shock-loading. Six laboratory-scale rising main reactors were subjected to three dosing schemes over a period of three months, namely (i) simultaneous caustic and oxygen addition, (ii) caustic addition and (iii) no chemical addition. Our results showed that the combination of caustic and oxygen achieved efficient sulfide control, leading to a prolonged biofilm recovery period in between caustic shocks. In addition, methane emissions were reduced to a negligible level compared to caustic treatment only. To translate the findings to real-life application, the key parameters obtained during the long-term lab-scale experiments were subjected to extensive simulation studies using the SeweX model under a wide range of conditions commonly found in sewers. Overall, this study highlights the potential of periodic shock-loading and intermittent oxygen injection as combined dosing strategy for efficient sulfide control in sewers.

Side stream treatment nitrogen removal: alternatives for New York City

New York City Environmental Protection (NYCEP) is in the process of upgrading its treatment plants for nitrogen removal and is treating centrate, the side stream emanating from the anaerobic digestion process separately (SCT). The City is currently using a multi prong approach to treat centrate. Currently it uses the conventional nitrification/denitrification process with caustic and carbon addition at some of the plants and has the world's largest SHARON® demonstration facility at one site. In addition, the City is exploring the use of the anammox process as a viable alternative to the above two processes. To this effect, a pilot MBBR partial nitritation/anammox (PNA) reactor was operated in conjunction with the City College of New York (CCNY) at the 26th Ward Waste Water Treatment Plant in Brooklyn, NY. PNA is a nitrogen removal process that has a low carbon footprint and fits a low energy framework exceedingly well with low aeration and no external carbon requirements. Conducting a cost comparison of the PNA process to the conventional SCT and the SHARON® process on a cost per pound of nitrogen removed basis, it is found that the operating costs for the PNA process is only 35% of the SCT and 65% of the SHARON®, thus delivering substantial savings to the City when adopted at full-scale for future decades.

Electrolytic extraction drives volatile fatty acid chain elongation through lactic acid and replaces chemical pH control in thin stillage fermentation

BackgroundVolatile fatty acids (VFA) are building blocks for the chemical industry. Sustainable, biological production is constrained by production and recovery costs, including the need for intensive pH correction. Membrane electrolysis has been developed as an in situ extraction technology tailored to the direct recovery of VFA from fermentation while stabilizing acidogenesis without caustic addition. A current applied across an anion exchange membrane reduces the fermentation broth (catholyte, water reduction: H2O + e− → ½ H2 + OH−) and drives carboxylate ions into a clean, concentrated VFA stream (anolyte, water oxidation: H2O → 2e− + 2 H+ + O2).ResultsIn this study, we fermented thin stillage to generate a mixed VFA extract without chemical pH control. Membrane electrolysis (0.1 A, 3.22 ± 0.60 V) extracted 28 ± 6 % of carboxylates generated per day (on a carbon basis) and completely replaced caustic control of pH, with no impact on the total carboxylate production amount or rate. Hydrogen generated from the applied current shifted the fermentation outcome from predominantly C2 and C3 VFA (64 ± 3 % of the total VFA present in the control) to majority of C4 to C6 (70 ± 12 % in the experiment), with identical proportions in the VFA acid extract. A strain related to Megasphaera elsdenii (maximum abundance of 57 %), a bacteria capable of producing mid-chain VFA at a high rate, was enriched by the applied current, alongside a stable community of Lactobacillus spp. (10 %), enabling chain elongation of VFA through lactic acid. A conversion of 30 ± 5 % VFA produced per sCOD fed (60 ± 10 % of the reactive fraction) was achieved, with a 50 ± 6 % reduction in suspended solids likely by electro-coagulation.ConclusionsVFA can be extracted directly from a fermentation broth by membrane electrolysis. The electrolytic water reduction products are utilized in the fermentation: OH− is used for pH control without added chemicals, and H2 is metabolized by species such as Megasphaera elsdenii to produce greater value, more reduced VFA. Electro-fermentation displays promise for generating added value chemical co-products from biorefinery sidestreams and wastes.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0396-7) contains supplementary material, which is available to authorized users.

Role of Caustic Addition in Bitumen–Clay Interactions

Coating of bitumen by clays, known as slime coating, is detrimental to bitumen recovery from oil sands using the warm slurry extraction process. Sodium hydroxide (caustic) is added to the extraction process to balance many competing processing challenges, which include undesirable slime coating. The current research aims at understanding the role of caustic addition in controlling interactions of bitumen with various types of model clays. The interaction potential was studied by quartz crystal microbalance with dissipation monitoring (QCM-D). After confirming the slime coating potential of montmorillonite clays on bitumen in the presence of calcium ions, the interaction of kaolinite and illite with bitumen was studied. To represent more closely the industrial applications, tailings water from bitumen extraction tests at different caustic dosage was used. At caustic dosage up to 0.5 wt % oil sands ore, a negligible coating of kaolinite on the bitumen was determined. However, at a lower level of caustic add...

Mechanical Vapor Recompression for the Treatment of Shale-Gas Flowback Water

Summary Used extensively by the food, chemical, and pharmaceutical industries, the mechanical-vapor-recompression (MVR) process is viewed as a reliable method for recovering demineralized water from concentrated brines. Devon Energy has supported the operation of an advanced MVR system at a north-central Texas (Barnett shale region) treatment facility. At this facility, pretreatment included caustic addition and clarification for total-suspended-solids and iron control. Pretreated shale-gas flowback water was then sent to three MVR units, each rated at 2,000–2500 B/D (318–398 m3/d). Data were collected during a 60-day period in the summer of 2010. Distilled-water recovery volume averaged 72.5% of the influent water to the MVR units. The influent total dissolved solids (TDS) fed to the MVR units averaged just under 50 000 mg/L. More than 99% of the TDS were captured in the concentrate stream. The fate of multivalent cations; total petroleum hydrocarbons (TPH); and benzene, toluene, ethylbenzene and xylenes (BTEX) throughout the treatment system was determined. Most of the iron and TPH removal (90 and 84%, respectively) occurred during pretreatment. The total removal of iron, magnesium, calcium, barium, and boron from the distillate exceeded 99%. BTEX removal from the distillate exceeded 95%. Electric power at the facility was provided by two natural-gas generators, and compressors associated with the MVR units were driven by natural-gas-fueled internal-combustion engines. Energy requirements at the entire treatment facility were tracked daily by total natural-gas use. Best-fit correlations between treated water and distillate production vs. total plant use of natural gas indicated that there was a base power load throughout the facility of approximately 120 to 140 Mscf/D (3400 to 3960 m3/d) of gas. Approximately 48 scf natural gas/bbl influent water treated (270 m3/m3 influent) or 60.5 scf/bbl distillate produced (340 m3/m3 distillate) was required; this represents an energy cost of less than USD 0.25/bbl treated (USD 0.04/m3 treated) and approximately USD 0.30/bbl of distillate product generated (USD 0.048/m3 distillate), assuming a natural-gas cost of USD 5/million Btu (USD 4.72/GJ). Performance in terms of water recovery and product-water quality was stable throughout the 60-day test.

A citrus waste-based biorefinery as a source of renewable energy: technical advances and analysis of engineering challenges

An assessment of recent technical advances on pretreatment processes and its effects on enzymatic hydrolysis as the main steps of a proposed citrus processing waste (CPW) biorefinery is presented. Engineering challenges and relevant gaps in scientific and technical information for reliable design, modeling and scale up of a CPW biorefinery are also discussed. Some integrated physico-chemical pretreatments are proposed for testing for CPW, including high speed knife-grinding and simultaneous caustic addition. These new proposed processes and the effect of parameters such as particle size, surface area and morphology, pore volume and chemical composition of the diverse fractions resulting from pretreatment and enzymatic hydrolysis need to be evaluated and compared for pretreated and untreated samples of grapefruit processing waste. This assessment suggests the potential for filling the data gaps, and preliminary results demonstrate that the reduction of particle size and the increased surface area for the CPW will result in higher reaction rates and monosaccharide yields for the pretreated waste material.

Sequestration of CO2 in Mixtures of Caustic Byproduct and Saline Waste Water

Ex-situ carbonation of mixtures of caustic byproduct materials and produced oil-field brine provides a niche opportunity to sequester anthropogenic CO2, while concomitantly reducing the basicity of the reactive slurry. A series of tests were conducted to investigate a novel reaction concept designed to achieve neutralization of mixtures of acidic oil field produced brine and caustic industrial byproducts while sequestering substantial quantities of anthropogenic carbon dioxide (CO2) in a mixed-flow reactor. Experiments were conducted to determine the CO2-bearing capacity of reactive mixtures of brine from the Oriskany Sandstone Formation with three caustic industrial byproducts: flue gas desulfurization (FGD) spray dryer ash, Class C fly ash subbituminous coal combustion byproduct, and bauxite residue slurry from the alumina production process. Reactions were conducted in a closed, well-mixed (1,500 rpm) reactor with gas composed of 29.46% vol./vol. CO2 balanced by nitrogen gas (N2) fed at a rate of 300 mL/min. Reactions were carried out at ambient conditions. Results show linear relationships between caustic byproduct addition and CO2-bearing capacity, with relatively small impact of brine addition as compared to deionized water addition. FGD spray dryer ash/brine mixtures exhibited higher CO2 reactivity than those using Class C fly ash (0.759 moles CO2, at 23.6% solids by weight and 0.036 moles CO2 at 23.3% solids by weight, respectively). Bauxite residue exhibited moderate capacities in mixtures with higher percent solids (0.335 moles CO2 in 40% solids bauxite residue slurry). Carbonation capacity of caustic byproduct/acidic brine mixtures was shown to increase linearly with respect to percent caustic byproduct addition, but enhanced mineral carbonate precipitation resulting from synergistic reaction of brine cations with increased dissolved carbonate species was not observed in the short term.

Effect of Caustic Addition in Epoxy Polymerization Process: A Single and Multi‐Objective Evolutionary Approach

AbstractSummary: An epoxy polymerization process is studied in semi‐batch mode. Caustic has a very critical influence on epoxy polymerization process, which is modeled as a set of highly nonlinear coupled ODE's (ordinary differential equations). Owing to the highly complicated, nonlinear domain of analysis, “Differential Evolution (DE)” and “Genetic Algorithm (GA)” are used as optimization tools to identify the $\overline M _{\rm n}$‐PDI Pareto set and study the best operating strategy with respect to NaOH addition. The moment of various oligomeric components during the semi‐batch polymerization is also presented for a better understanding of the process. This study demonstrates the potential of evolutionary optimization algorithm to identify various operating philosophies of a semi‐batch epoxy reactor for a targeted product quality.Pareto plot for epoxy polymerization process with intermediate NaOH addition varying from 0.0 to 1.0 kmol · m−3.imagePareto plot for epoxy polymerization process with intermediate NaOH addition varying from 0.0 to 1.0 kmol · m−3.

Release of phosphorus from biological nutrient removal sludges: A study of sludge pretreatment methods to optimize phosphorus release for subsequent recovery purposes

As part of on-going studies related to development–implementation of new technologies and approaches for enhancing recovery of phosphorus from municipal wastes, the effectiveness of various methods of pretreating waste activated sludges (WASs) from a biological nutrient removal (BNR) process was investigated to determine suitable methods for maximizing phosphorus release. The additions of a strong base (NaOH), strong acid (HCl), organic acid (citric acid), and sodium acetate to waste sludge all facilitated the release of phosphate into solution. The maximum phosphate release was obtained by adding 4.9 mmole/L (~400 mg/L) of acetate to an intermittently mixed digester. Excess amounts of acetate did not further increase the phosphate concentrations. Acetate addition, which triggers carbon storage, a unique characteristic of enhanced biological phosphorus removal (EBPR) processes, releases internally stored phosphate compounds and is recommended as a method for releasing phosphates from EBPR sludges. Along with phosphates, various cations (most notably magnesium and potassium) were also mobilized and released into solution during digestion using acetate. These ions can be beneficially reused for struvite crystallization. Key words: acetate addition, caustic addition, phosphorus release, P-solubilization, sludge treatment, struvite.

Miscella refining test method for the determination of cottonseed oil color

AbstractMost of the cottonseed oil mills in the United States have already converted to expander solvent extraction and miscella refining. This practice permits mills to produce and market a consistently light‐colored, prime bleachable summer yellow cottonseed oil at reduced cost and refining loss. A laboratory‐scale miscella refining test was developed to asses the oil quality in terms of its color. The test involves the addition of 3 parts oleic acid per 100 parts of crude oil in the miscella followed by refining with 2.5 parts NaOH when crude oil contains less than 4.5% free fatty acid (FFA). When crude oil contains FFA between 4.5 and 7.5%, no oleic acid is added prior to refining with 2.5 parts NaOH. When crude oil contains FFA higher than 7.5%, no oleic acid is added and the caustic addition table in American Oil Chemists' Society Method Ca 9a‐52 is followed. The test was conducted at room temperature and gave reproducible colors comparable to commercially refined oils.

Effect of reaction conditions on molten-caustic leaching of oil-sand coke residues

The effect of reaction conditions on the desulfurization of oil-sand coke residues was studied. The variables investigated were temperature, reaction time, heat-transfer resistance and mode of caustic soda addition. The results show that oil-sand coke de sulfurization increases with temperature, reaction time and heat-transfer rate. In an oxidative environment, coke combustion during molten-caustic leaching (MCL) commences at temperatures above 500 °C. The mode of caustic addition has no effect on coke desulfurization.

Application of a permeant/polymer diffusional model to the desorption of polychlorinated biphenyls from Hudson River sediments

The desorption of polychlorinated biphenyls (PCBs) from Hudson River sediments was examined using XAD-4 resin as a PCB adsorbent. Both a rapidly desorbing labile component and a more slowly desorbing resistant component were observed. The fraction of PCBs in the resistant component was found to be a function of PCB concentration and total organic carbon in the sediment, independent of inorganic particle size. Milling the sediment had no effect on PCB desorption, while pretreatment of the sediment using heat (with and without caustic addition) enhanced the rate ofdesorption and significantly decreased the resistant fraction. We propose that the labile and resistant fractions arise from disparate diffusional rates of PCBs from the swollen and condensed phases of the sediment organic matter