Dilute Aqueous Streams Research Articles

Supported liquid membrane with selective stripping for separative recovery of copper and zinc from plating wastewater

For separation and recovery of different but chemically similar metal from dilute wastewater with reduced process complexity and cost, a supported liquid membrane (SLM) system that utilizes a single carrier together with strip dispersion for selective stripping of coextracted metal ions was proposed to enable concurrent separation and recovery. This study aims to investigate the effectiveness of the proposed SLM system for separative recovery of copper and zinc from real plating wastewater. Solvent extraction experiments were conducted to understand the effect of feed pH and carrier concentration on organic phase migration to the aqueous phase. The effect of stirring speed on the SLM transport rate was studied using synthetic feed. Combined with the insights from our previous study, appropriate settings were identified and applied to the SLM system. The SLM system could recover 83.7% copper with 91.0% purity and 85.5% Zn with 99.3% purity from the plating wastewater in 30 h. The findings indicate the feasibility of using SLM with selective stripping for the concurrent separation and recovery of copper and zinc from a dilute aqueous waste stream predominantly containing these two metals.

Simple and Low-Cost Electroactive Membranes for Ammonia Recovery.

Ammonia is considered a contaminant to be removed from wastewater. However, ammonia is a valuable commodity chemical used as the primary feedstock for fertilizer manufacturing. Here we describe a simple and low-cost ammonia gas stripping membrane capable of recovering ammonia from wastewater. The material is composed of an electrically conducting porous carbon cloth coupled to a porous hydrophobic polypropylene support, that together form an electrically conductive membrane (ECM). When a cathodic potential is applied to the ECM surface, hydroxide ions are produced at the water-ECM interface, which transforms ammonium ions into higher-volatility ammonia that is stripped across the hydrophobic membrane material using an acid-stripping solution. The simple structure, low cost, and easy fabrication process make the ECM an attractive material for ammonia recovery from dilute aqueous streams, such as wastewater. When paired with an anode and immersed into a reactor containing synthetic wastewater (with an acid-stripping solution providing the driving force for ammonia transport), the ECM achieved an ammonia flux of 141.3 ± 14.0 g.cm-2.day-1 at a current density of 6.25 mA.cm-2 (69.2 ± 5.3 kg(NH3-N)/kWh). It was found that the ammonia flux was sensitive to the current density and acid circulation rate.

Recovery of dilute (bio-based) volatile fatty acids by adsorption with magnetic hyperthermal swing desorption

Adsorption followed by stepwise desorption to concentrate volatile fatty acids (VFAs) from very dilute aqueous streams is challenging and only a limited amount of VFAs can be collected at high concentration using N2-stripping. Here, we describe the preparation and use of superparamagnetic porous adsorbents to recover much larger fractions of VFAs in highly concentrated form from dilute aqueous streams than with the state-of-the-art N2-stripping technique. Our system is based on poly(divinylbenzene) (PDVB) impregnated with superparamagnetic magnetite nanoparticles (MNPs) synthesized by coprecipitation and functionalized with oleic acid (OA). The OA grafted MNPs (OA-MNPs) were embedded in the matrix of the polymer during suspension polymerization. The porous particles had an average size of 222 ± 40 µm with a surface area of 496 ± 10 m2/g and contained 11 ± 1 wt% MNPs with an average core size of 10 nm. VFAs adsorption from a dilute aqueous solution (containing 0.25 wt% of each acid) reached a saturation capacity of 43 g carboxylic acid per kg adsorbent,. The two-stage desorption was started with alternating magnetic field (AMF) heating at 25 mT and 52 kHz, followed by a hot N2 stripping stage removed 90 ± 9% of the water that had physically filled the pores during adsorption, and only 11 ± 2% of the loaded VFAs. Subsequently, 89 ± 3% of the VFAs were recovered almost water free using hot N2 stripping. Compared to sorbent regeneration and vapor fractionation by nitrogen stripping with a temperature gradient only, this new approach offers a much sharper acid fractionation from water, facilitating large energy savings in downstream operations.

Experimental, equilibrium modelling, and column design for the reactive separation of biomass‐derived 2‐furoic acid

AbstractElectrochemical conversion of biomass to value‐added chemicals has gained impetus in recent years. Herein, we present a methodology for recovering biomass‐derived 2‐furoic acid from the dilute aqueous stream by reactive extraction. The reactive extraction was performed using a chemical extractant, trioctylamine (TOA), with diluents (octanol, chloroform, and diethyl ether). Equilibrium parameters influencing the recovery of 2‐furoic acid were evaluated. Using TOA in various diluents, the 2‐furoic acid was recovered with 85%–99% efficiency. A 1:1 complex of the 2‐furoic acid—TOA was formed in the organic phase, and the experimental equilibrium complexation constant was compared with that obtained from the relative basicity and Langmuir models. The equilibrium parameters were used for column design to estimate the solvent to feed ratio (S/F) and the number of theoretical stages (NTS). The NTS required is 12 to attain 99% recovery of 2‐furoic acid in counter‐current extraction. The present study sheds light on the reactive extraction process adopted for process intensification with electrochemical conversion, paving the way for the commercialization of valuable products obtained from biomass.

Reactive Distillation for Solvent Regeneration after Biphasic Carboxylic Acid Esterification

AbstractEmulsion‐enhanced biphasic esterification has proven to be applicable for carboxylic acid recovery from dilute aqueous process streams. The carboxylic acid is esterified with 1‐octanol in an emulsified regime with 4‐dodecylbenzenesulfonic acid (4‐DBSA) or Ni(DBSA)2 as catalyst. After phase separation, the laden solvent phase must be regenerated. This study presents a regeneration concept based on reactive distillation with transesterification of the octyl ester‐laden solvent with methanol. The regenerated solvent is reused in the extraction step.

Conceptual design of a dual reactive dividing wall column for downstream processing of lactic acid

Methodologies for designing intensified processing units are necessary to enable the industrial application of process intensification concepts. This article presents a ruled-based systematic methodology for the synthesis and conceptual design of a dual reactive dividing wall column (dual R-DWC). A decomposition approach is used to identify the tasks required for the separation by introducing a reactive separating agent to exploit a reversible reaction to enhance the driving forces. A combination of shortcut and rigorous simulations led to the conceptual design of a novel dual R-DWC in which the forward and reverse reactions and the separation occur at once.The methodology was demonstrated in a case study for the separation of lactic acid from dilute aqueous streams and a reactive impurity that hinders the lactic acid conversion and its recovery, while the byproducts may bring new challenges for the desired separations.This study is the first to investigate the effect of reactive impurities on the reaction and the separation, hence adding a more realistic framework to the design. The flowsheet produced was evaluated against benchmark processes and showed a significant process improvement in terms of energy savings (ranging 13-27 %), material intensity (28-32 % reduction), and water consumption (22-36 % reduction), while the reactive impurities are effectively removed.

Vapor–liquid behavior of phenol and cumene in ternary and quaternary mixtures

AbstractBACKGROUNDAlthough phenol is a key intermediate in the plastics and polycarbonate industry, it is also a toxic component that requires removal from dilute aqueous streams, potentially by liquid–liquid extraction (LLX). For LLX, cumene is suggested as a solvent as it is already present in processes in the polycarbonate industry. For the recovery of cumene from phenol by distillation, knowledge on vapor–liquid equilibrium (VLE) behavior is important, in combination with how this is affected by other components possibly present as an impurity or explicitly added as a solvent. This was investigated in this work.RESULTSThe binary cumene–phenol system shows a tangent pinch in the binary VLE diagram. Addition of a range of impurities and solvents showed that hydrogen bond accepting compounds strongly improve the relative volatility of the mixture, whereas dodecane, not capable of forming hydrogen bonds, has a negative effect on the relative volatility.CONCLUSIONAddition of polar components with hydrogen bonding abilities, i.e. ketones or ethers, affected the relative volatility of cumene over phenol the most positively. Combining two types of components results in similar effects, and clear synergistic effects could not be shown based on current VLE measurements. Addition of an apolar component in combination with polar components with hydrogen abilities had only a minor effect on the relative volatility. © 2021 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Novel Hybrid Reactive Distillation with Extraction and Distillation Processes for Furfural Production from an Actual Xylose Solution

Furfural is only derived from lignocellulosic biomass and is an important chemical used in the plastics, agrochemical, and pharmaceutical industries. The existing industrial furfural production process, involving reaction and purification steps, suffers from a low yield and intensive energy use. Hence, major improvements are needed to sustainably upgrade the furfural production process. In this study, the conventional furfural process based on a continuous stirred tank reactor and distillation columns was designed and optimized from an actual aqueous xylose solution via a biomass pretreatment step. Subsequently, a reactive distillation (RD) and extraction/distillation (ED) configuration was proposed for the reaction and purification steps, respectively, to improve the process efficiency. RD can remove furfural instantly from the reactive liquid phase and can separate heavy components from the raw furfural stream, while the ED configuration with toluene and butyl chloride used as extracting solvents can effectively separate furfural from a dilute aqueous stream. The results showed that the hybrid RD-ED process using a butyl chloride solvent saves up to 51.8% and 57.4% of the total investment costs and total annual costs, respectively, compared to the conventional process. Furthermore, environmental impacts were evaluated and compared for all structural alternatives.

Removal of Cadmium, Zinc, and Manganese from Dilute Aqueous Solutions by Foam Separation

As environmental regulations are becoming stricter, new techniques must be developed for the removal of trace concentrations of heavy metals from mineral processing effluents. Foam separation techniques are an interesting alternative to more conventional processes such as ion exchange because of their efficiency to treat dilute aqueous streams. In this paper, the simultaneous removal of Cd2+, Mn2+, and Zn2+ from dilute aqueous solutions was investigated by using sodium dodecyl sulfate as collector and triethylenetetramine as auxiliary ligand via a series of batch-mode flotation experiments. Experimental results showed that Cd2+, Mn2+, and Zn2+ can be completely removed in one step under the following conditions: pH 9.50, flotation time = 120 min, auxiliary concentration 0.1 mmol L−1, collector-to-metals molar ratio 2:1, ethanol concentration 0.5% (v/v), and a nitrogen gas flowrate set at 25 mL min−1. An excess in auxiliary ligand concentration yielded to low removal efficiency. The modeled speciation of the examined system suggested that the metals are separated from the bulk solution to the foam phase via a combination of ion flotation and precipitate flotation.Graphical Abstract

Experimental perspective for reactive separation of malonic acid using TBP in natural non-toxic solvents

Recent technological advancement allows the synthesis of malonic acid from the bio-fermentation route by using cost-effective raw material like biomass, which enhances its overall production. The dilute aqueous stream of malonic acid produced from the biological route needs to be recovered. Process intensification with precise operating conditions and low toxicity such as reactive separation is applied for extraction of malonic acid from the dilute aqueous stream by using non-toxic natural solvents like canola oil, sunflower oil, and soybean oil with the tributyl phosphate (TBP) extractant. An in-depth experimental analysis is performed in the present study to evaluate extraction complexation equilibrium constant (KE(MA)), extraction efficiency (E(MA)%), distribution coefficient (KD(MA)), and loading ratio (Z(MA)). The overall loading ratio is less than 0.5 for all solvents, which signifies the formation of 1:1 complexation. KD(MA) and E(MA)% with soybean oil are in range of 0.265–0.832, and 20.683–43.850, for sunflower oil is 0.208–0.763 and 17.227–42.340, for canola oil is 0.301–0.875 and 22.878–45.106. The behavior of TBP-malonic acid complexation equilibrium in the reactive separation process is predicted by comparing relative basicity model values with experimental outputs. The separation process requires a continuous column operation, and the number of transfer stages is evaluated to be 2. Furthermore, the diffusion coefficients (D(MA)) of malonic acid to the natural, non-toxic solvents with variable TBP concentrations are evaluated by employing various empirical correlations. The present study paves the way for future research in continuous in-situ product recovery of malonic acid produced via biological route.

Statistical Optimization of Lactic Acid Extraction Using Green Solvent and Mixed Extractants (TOA and TOMAC)

Since some previous years, reactive extraction has become more attractive and competitive technique for the separation and purification of lower carboxylic acids from fermentation broth as well as from dilute aqueous streams. This paper shows the results of investigation of reactive extraction of lactic acid (LA) from an aqueous solution using the synergistic mixture of the extractants (TOA (tri-n-octylamine) and TOMAC (Tri-n-octylmethylammonium chloride)) and a non-toxic and biocompatible green solvent (soybean oil). Three-level Box-Behnken design (BBD) under response surface methodology (RSM) was opted for the experimental design and to interpret the mutual effect of seven independent process parameters on the LA distribution coefficient (KD). The maximum values of LA distribution coefficient (KD=2.51) and its extraction efficiency (ηη=71.5%) were obtained for the optimum values of various process parameters such as 0.02 [M] initial LA concentration (CC1), 0.5 (v/v) extractant ratio (α), 28.66% (v/v) mixed extractants concentration (ψ), 2 (v/v) phase ratio (φ), 270C temperature (T), 102 rpm stirring speed (ω), and 63 mincontact time (τ). This present investigation will provide a noble discussion on LA reactive extraction using green solvent and on various influencing process parameters for gaining the enhanced value of LA distribution coefficient (KD).
 Chemical Engineering Research Bulletin 21(2019) 20-35

Reactive Extraction of Malic Acid using Trioctylamine in 1\u2013Decanol: Equilibrium Studies by Response Surface Methodology Using Box Behnken Optimization Technique

Reactive extraction is a significant technique employed for the removal of organic acids such as carboxylic acid which are usually present in low concentrations in aqueous solutions. This technique was explored by applying Response Surface Methodology (RSM) in process parameter optimization for malic acid recovery from aqueous streams using Trioctylamine as extractant and 1-decanol as organic diluent. Malic acid, a C4 dicarboxylic acid has a wide variety of applications in the polymer, food, chemical and pharmaceutical industries. The optimization of the response function: extraction efficiency was systematically carried out using three process parameters for reactive extraction: temperature, initial malic acid concentration and extractant (Trioctylamine) composition. Response Surface Methodology in combination with Box-Behnken design involving seventeen experimental runs was employed for malic acid reactive extraction in this study. A statistical second-order polynomial predicted an extraction efficiency of 97.53%. The optimum conditions of the process variables were found to be: temperature: 304.73 K, acid concentration: 0.25 kmol/m3, Trioctylamine composition: 23.54% (v/v). Under these optimum conditions, the experimental response of extraction efficiency of 93.25% was obtained. The experimental results obtained was in close conformity with the predicted values by numerical optimization using Response Surface Methodology. These findings can pave the way for the reactive separation process design for recovery of carboxylic acids from dilute aqueous waste streams as well as a fermentation broth.

Reactive extraction of propionic acid using trioctylamine in 1–decanol by response surface methodology optimization technique

Abstract Reactive extraction, a novel technique, was experimentally investigated for the removal of propionic acid, which is usually present in low concentrations in aqueous solutions. The experiments were conducted according to statistical design to develop an appropriate regression model. This was aimed at analyzing and optimizing the process variables and extraction efficiency for propionic acid reactive extraction from dilute aqueous streams using trioctylamine as extractant and 1-decanol as organic diluent. Response surface methodology in combination with Box–Behnken design involving 17 experimental runs was utilized for the propionic acid reactive extraction in this study. Three independent process variables were chosen as temperature (T), initial propionic acid concentration (CPAO) in the aqueous phase and trioctylamine composition (CTOA) in the organic phase. The statistical design analysis demonstrated that the propionic acid concentration and TOA composition had a significant effect while temperature had an insignificant effect on the response value as well as an interactive and quadratic effect on the response. The optimum conditions for propionic acid extraction were established as T = 300.752 K, CTOA = 18.252 %v/v, CPAO = 0.408 kmol/m3. Under these optimum conditions, the propionic acid experimental extraction yield was 89.788 %, which was in close conformity with the predicted yield value of 91.939 %.

Adsorption performance of packed bed column for benzylformic acid removal using CaO2 nanoparticles

Abstract A packed bed column for the recovery of benzylformic acid from the dilute aqueous stream was operated using CaO2 nanoparticles adsorbent. CaO2 nanoparticles were synthesized and characterized by XRD and HR-FESEM. HR-FESEM confirmed that the average size of 32 nm for CaO2. The adsorption breakthrough curve was determined by varying the operating parameters: initial benzylformic acid concentration (9.53–13.47 mg/mL), flow rate (2.5–3.5 mL/min), and bed height (10–20 cm). The bed depth service time (BDST) model at 40%, 50%, and 90% breakthrough provided a good fit to experimental data. Five mathematical models; Thomas, Yoon–Nelson, Clark, Bohart–Adams, Wolborska model was applied to the experimental data using linear regression and the optimum parameters of the column were determined. Analysis of the regression coefficients indicated that the regressed lines provided excellent fits to the experimental data with R2 values ranging from 0.947–0.996 using Thomas model. The experimental and predicted breakthrough time (tb) value of Thomas is in close agreement than Yoon–Nelson, Clark, Bohart–Adams and Wolborska models. The Thomas has been found more appropriate for α-toluic acid removal in a packed bed column. The results are useful for the design of packed column for adsorption, which can be further extended to other systems.

Reactive Extraction of Gallic Acid Using Tributyl Phosphate in Different Classes of Diluents

Gallic acid is an important carboxylic acid used in pharmaceutical industries owing to its medicinal properties. The separation of gallic acid from fermentation broth and dilute aqueous streams is a challenging task. Therefore, in the present study the reactive extraction of gallic acid from an aqueous solution by using tributyl phosphate in octanol, ethyl acetate, n-hexane, and toluene as diluents, respectively, has been carried out at constant temperature (303 ± 1 K). The results were compared with those of the extraction using pure diluents in order to compute the intensification of extraction obtained. Experiments were performed to investigate the effect of initial acid concentration, extractant concentration, and diluent type. TBP + hexane was found to be most suitable solvent system resulting in the highest distribution coefficient (KD = 24) when TBP was employed at a concentration of 1.516 mol·kg–1. The equilibrium complexation constant (KE) was observed to be in the ranges of 3.18–8.8 for n-hexane...

Experimental Study on Reactive Extraction of Malonic Acid with Validation by Fourier Transform Infrared Spectroscopy

Malonic acid is an essential carboxylic acid that is used as a backbone reactant in deriving multiple higher-order carboxylic compounds. The successful attempt of producing malonic acid from a biological route has attracted the scientific community to extract malonic acid from a fermentation broth or dilute aqueous stream. Experimental study on the recovery of malonic acid by reactive extraction was performed, and the effects of TBP concentration, diluents (alkane, ketone, and alcohol), and malonic acid concentration were investigated. The equilibrium models (relative basicity and mass action law models) and the number of theoretical units (NTU) were also evaluated. Fourier transform infrared spectroscopy provided evidence for the formation of significant bonds among extractant–diluent–acid complexation systems which support the experimental outcomes. The results of extraction equilibrium are discussed regarding dimerization constant (DMA), partition coefficient (PMA), extraction efficiency (EMA%), distri...

Water-Based Synthesis of Hydrophobic Ionic Liquids [N8888][oleate] and [P666,14][oleate] and their Bioprocess Compatibility.

The conversion of organic waste streams into carboxylic acids as renewable feedstocks results in relatively dilute aqueous streams. Carboxylic acids can be recovered from such streams by using liquid–liquid extraction. Hydrophobic ionic liquids (ILs) are novel extractants that can be used for carboxylic acid recovery. To integrate these ILs as in situ extractants in several biotechnological applications, the IL must be compatible with the bioprocesses. Herein the ILs [P666,14][oleate] and [N8888][oleate] were synthesized in water and their bioprocess compatibility was assessed by temporary exposure to an aqueous phase that contained methanogenic granular sludge. After transfer of the sludge into fresh medium, [P666,14][oleate]‐exposed granules were completely inhibited. Granules exposed to [N8888][oleate] sustained anaerobic digestion activity, albeit moderately reduced. The IL contaminants, bromide (5–500 ppm) and oleate (10–4000 ppm), were shown not to inhibit the methanogenic conversion of acetate. [P666,14] was identified as a bioprocess‐incompatible component. However, our results showed that [N8888][oleate] was bioprocess compatible and, therefore, has potential applications in bioprocesses.

Ion Transport and Competition Effects on NaTi2(PO4)3 and Na4Mn9O18 Selective Insertion Electrode Performance.

We evaluate the efficiency and capacity of electrochemically reversible insertion electrodes for use in targeted ion removal applications in aqueous solutions. The relative attributes of insertion material chemistry are evaluated by comparing the performance of two different sodium insertion materials, NaTi2(PO4)3 and Na4Mn9O18, in different electrolyte environments. We performed experiments over a range of solution compositions containing both sodium and other non-inserting ions, and we then developed mechanistic insight into the effects of solution concentration and composition on overpotential losses and round trip Coulombic efficiency. In dilute aqueous streams, performance was limited by the rate of ion transport from the bulk electrolyte region to the electrode interface. This leads to slow rates of ion removal, large overpotentials for ion insertion, parasitic charge loss due to water electrolysis, and lower round trip Coulombic efficiencies. This effect is particularly large for insertion electrodes with redox potentials exceeding the water stability window. In solutions with high background concentrations of non-inserting ions, the accumulation of non-inserting ions at the electrode interface limits inserting ion flux and leads to low ion removal capacity and round trip Coulombic efficiency.

Chemical vs. Biological Crystals, all the Same?

Using microorganisms to mediate crystallisation of metals and minerals in open-culture bioreactors has potential to recover recyclable materials from dilute aqueous streams, but also to prevent their emission to the environment. Although this potential is already exploited in practice to some extent, biological crystallization for metal recovery is still largely a black box technology with limited understanding of the role of the microorganisms in the crystallization, and the differences with chemical crystallisation. Using biocrystallisation of scorodite (FeAsO4.2H2O) and sphalerite (ZnS) as examples we propose that the role of microorganisms strongly depends on established saturation state of the solution. For scorodite, microorganisms are used to exert control over the crystallization as their ferrous iron-oxidizing activity keeps the solution slightly oversaturated. Also, the oversaturation level is kept homogeneous because of continuous biological formation of the reactant ferrous iron throughout the solution. In continuous bioreactor experiments on which we reported previously, scorodite crystal sizes still increased after 72 days of bioreactor operation indicating that indeed crystal growth was favored over nucleation. On the other hand, in our experiments with zinc sulfide, crystallization proceeded in highly oversaturated solutions in a continuous sulfate reducing bioreactor fed with a zinc sulfate solution and H2/CO2 as electron donor and carbon source. The high oversaturation likely resulted in dominant primary nucleation in the bulk solution, with little or no control over crystal growth, even though agglomeration may still have occurred. This was exemplified by particle sizes which decreased in the bioreactor experiment and remained stable after already about 2 weeks of operation.

Removal of pyridine from dilute aqueous streams using hollow fiber supported liquid membranes

The removal of pyridine from aqueous phase using hollow fiber supported liquid membranes has been investigated. Effect of several parameters such as feed concentration, extractant concentration, type of extractants, etc. has been studied. Organic solvents such as, 2-nonyl phenol (2-NP), 4-nonyl phenol (4-NP), stearic acid (SA), and di-(2-ethylhexyl) phosphoric acid (D2EHPA) were used as extractants. It was observed that the initial flux of pyridine increased with an increase in extractant concentration. The investigations showed that phenolic-based extractants (4-NP or 2-NP) were better for pyridine removal as compared to other extractants. The equilibrium experiments have been carried out by varying stirring speed and time in order to find the reaction kinetics and equilibrium time. Mass transfer-based model was used to explain the removal of pyridine for three different modules. Scale-up experiment shows nearly similar flux values of pyridine at both the scales. The model results were found to be in good agreement with the experimental observations. The results have been explained on the basis of steric effects, acidity of the extractant molecules along with the overall mass transfer resistance for the transport of pyridine.