Aqueous Streams Research Articles

Co-Fermenting Pyrolysis Aqueous Condensate and Pyrolysis Syngas with Anaerobic Microbial Communities Enables L-Malate Production in a Secondary Fermentative Stage

The pyrolytic conversion of lignocellulosic biomass into fuels and chemicals is a promising option for the valorization of agricultural and forestry residues. However, technological developments are still needed to maximize product recovery and carbon fixation of the pyrolysis process. The pyrolysis aqueous condensate (PAC), a pyrolysis by-product, has a high water content and is highly toxic, hampering its use. The anaerobic digestion of PAC from different biomasses has been proven a viable technology for PAC valorization and detoxification, but its toxicity limits the methanogenic potential. Alternatively, methanation or VFA production from syngas by anaerobic mixed cultures are technologies of scientific interest. This study investigates the potential of a two-stage process to convert the carbon and energy in syngas and PAC into L-malate. PAC and syngas were co-fermented by two mixed cultures at 37 and 55 °C, identifying kinetic inhibitions and the effects of increasing PAC concentrations on the product pool. The media from selected mixed culture fermentations were then inoculated with Aspergillus oryzae for L-malate production. The results show that mixed cultures can perform simultaneous syngas fermentation and PAC detoxification. While PAC concentrations above 2% completely inhibited methanogenesis, CO consumption was inhibited at PAC concentrations above 5%, regardless of the temperature. In fermentations where PAC inhibited methanation, the mixed cultures channelled the carbon and electrons from syngas and PAC to volatile fatty acids or acetate/H2 production, depending on the incubation temperature. Substantial detoxification of PAC was observed under PAC concentrations up to 10% independently of the rates of syngas metabolism. PAC detoxification enabled the further valorization of the acetate produced via syngas and PAC fermentations into L-malate, achieving yields up to 0.17 mM/mM. These results are promising for the development of an integrated process that simultaneously detoxifies and recovers value from gaseous and aqueous waste streams originating from pyrolysis.

Preparation and Performance of PU/Cpsf Blend Ultrafiltration Membranes for Removal of Heavy Metal Ion Rejection Studies

The performance of membranes for a specific application can be determined with the help of structural properties such as molecular weight cut-off (MWCO), morphology, and pore statistics. Heavy metal ions from aqueous streams can be separated with the help of ultrafiltration membranes. In the presence and absence of the various components of the additive poly (ethylene glycol) 600, MWCOs and pore statistics of polyurethane (PU) and carboxylated polysulfone (CPSf) blend ultrafiltration (Total Polymer Concentration = 17.5 wt %) were studied with the help of dextran of different molecular weights ranging from 19 kDa to 150 kDa. The derived pore size, porosity, and the number of pores have a remarkable relationship with the MWCO, morphology, and the flux performance of the membranes. The blend membranes rejected certain toxic divalent heavy metal ions such as copper, cadmium, nickel, and zinc by complexing them into a polymeric ligand, poly(ethyleneimine) (PEI). The effect of polymer blend compositions and additive concentrations on metal ions' rejection and permeate flux are discussed

Utilisation of Ammonium Carbonate in a Solid Oxide Cell

Production of coke required for steel manufacturing generates coke oven gas (COG) as by-product. Cleaning of COG yields an aqueous waste stream containing ammonia, water, phenol, carbon dioxide and trace components. Currently, this waste stream is disposed of by incineration. Due to the presence of carbon dioxide, a significant fraction of the ammonia is present as ammonium carbonate, (NH4)2CO3. This work investigates the utilisation of aqueous (NH4)2CO3 in a commercially-available solid oxide cell at 750 °C. The cell performance was characterised by current-voltage (I-V) curves and was shown to have excellent electrical performance in electrolysis mode. Online quadrupole mass spectrometry (QMS) measurements show (NH4)2CO3 catalytically decomposed to form nitrogen, hydrogen and carbon dioxide, with electrolysis at 1.4 V increasing hydrogen production by 50 vol%. The cell had very good performance in fuel cell mode, although this was tempered due to OCV losses caused by the carbon dioxide present.

Coupled Adsorption and Surface-Bound Radical-Mediated Oxidation on Biomass-Derived Porous Carbon: A Selective Approach for Sulfamethoxazole Removal

The development of selective oxidation processes is significant for the efficient removal of organic micropollutants from aqueous streams. Here, we propose a novel catalytic system that involves highly efficient adsorption followed by surface radical-mediated oxidation via conjunction of biomass-derived porous carbon (BPC) and peroxydisulfate (PDS). A series of BPC samples were prepared via pyrolyzing biomass at different temperatures (600 °C, 700 °C, 800 °C). BPC800 had the best reactivity for sulfamethoxazole removal: The maximum adsorption capacity of BPC800 was 529.3 mg/g, which is more than four times that of activated carbon (125.4 mg/g). The co-presence of PDS changed the major removing mechanism from adsorption to degradation. Mechanistic studies using quenching tests, electrochemical characterization, and fluorescence microscopy showed that surface-bound radicals were the dominant reactive species. Efficient performance was also achieved during the treatment of real wastewater and several other micropollutants. The results suggest a novel approach for highly-efficient selective removal of micropollutants from polluted wastewater and offer new insights into the generation of reactive species during the activation of PDS by carbonaceous materials.

LED based optical dip-probe spectrophotometer for in situ monitoring of uranyl and uranous ions in aqueous process stream

A miniature setup for the “transmission absorption spectrophotometry” was developed for in situ monitoring of U(VI) and U(IV) concentrations in the aqueous process streams of extraction, conversion, reprocessing, refinement and electro-chemical production of U(IV). The miniature setup used in the present work consisted of a LED light source (λmax = 471.5 nm for U(VI) and 665 nm for U(IV)), miniature spectrophotometer, mirror fitted and PEEK sheath protected dip-probe assembly or flow cell, and optical fibers with connectors. The characteristics absorbance peaks of U(VI) were used for concentration monitoring in the samples taken from the aqueous feed of uranium extraction process. There was a reasonable good agreement in the sensitivity values obtained by using the flow cell, dip probe and cuvette at 415, 466, and 485 nm having upper measurement limits of 25, 100 and 400 g/L of U(VI), respectively, in 2 mol/L HNO3. The absorbance peak at 485 nm did not exhibit any significant dependency on the HNO3 concentrations ranging from 0.5 to 3 mol/L. However, other absorbance peaks varied with the HNO3 concentrations. The various parameters such as effect of variation in HNO3 concentration and analytical range of the uranium concentration in the feed were studied. The robustness and analytical performance of the present method were studied by statistically analyzing the results of the real off-line samples from different batches of the feed of uranium extraction plant. From the results of statistical analyses, it could be seen that the measured U(VI) concentrations were in the good agreement with the other off-line methods such as gamma spectrometry, EDXRF and ICP-AES, and all the measured U(VI) concentrations results obtained were within ± 3σ values. There was no observable bias in the results with respect to concentration, acidity, date of experiment etc. This setup was also studied for the continuous monitoring of the production of U(IV) from the electrolytic reduction of U(VI) by monitoring 665 nm absorbance peak using a LED light source.

Theoretical and Experimental Considerations for Investigating Multicomponent Diffusion in Hydrated, Dense Polymer Membranes.

In many applications of hydrated, dense polymer membranes—including fuel cells, desalination, molecular separations, electrolyzers, and solar fuels devices—the membrane is challenged with aqueous streams that contain multiple solutes. The presence of multiple solutes presents a complex process because each solute can have different interactions with the polymer membrane and with other solutes, which collectively determine the transport behavior and separation performance that is observed. It is critical to understand the theoretical framework behind and experimental considerations for understanding how the presence of multiple solutes impacts diffusion, and thereby, the design of membranes. Here, we review models for multicomponent diffusion in the context of the solution-diffusion framework and the associated experiments for characterizing multicomponent transport using diffusion cells. Notably, multicomponent effects are typically not considered when discussing or investigating transport in dense, hydrated polymer membranes, however recent research has shown that these effects can be large and important for understanding the transport behavior.

Biosorption and biomagnetic recovery of La3+ by Magnetospirillum magneticum AMB-1 biomass

Biosorption is a simple, efficient, and eco-friendly method for aqueous waste stream treatment. However, the main drawback is the need for biomass removal after adsorption, which can be expensive and energy intensive. In the present study, biomass from the magnetotactic bacterium Magnetospirillum magneticum AMB-1 is evaluated for trivalent lanthanum (La3+) removal and recovery from an aqueous solution, as this naturally magnetic biomass can be easily separated from solution after adsorption using an external magnet. This is the first report of this common magnetotactic strain utilized for biosorption of a rare earth element. The adsorption capacity is 6.0 ± 0.15 mg La3+/g wet biomass (37.2 ± 1.2 mg La3+/g dry biomass) using 10 g/L AMB-1 wet biomass (1.6 g/L dry basis) in a 100 mg/L La3+ solution at pH 6.0, which is greater than that reported for some other bacterial species. Only a minor decrease in biosorption is observed when the salinity is increased to 1.5 M NaCl, and temperature variations up to 50 °C have little to no impact, suggestive of potential applications for biosorption from saline waste streams. The equilibrium biosorption data best fits the Langmuir isotherm model, and thermodynamic analysis indicates thermodynamically favorable lanthanum binding to AMB-1. Binding of La3+ to the AMB-1 biomass occurs through carboxyl, phosphate, and amide functional groups naturally present in the biomass. AMB-1 biomass can be used for at least five rounds of La3+ adsorption and desorption, as well as the separation and concentration of a mixture of rare earth elements. Rapid adsorption and desorption times of 8 min, as well as a simple magnetic separation, make M. magneticum AMB-1 biomass a promising biosorbent for rare earth metals in aqueous waste streams.

Polyaniline/Multi Walled Carbon Nanotubes-A Promising Photocatalyst Composite for Reactive Blue 4 Oxidation.

For the photocatalytic removal of the Reactive Blue 4 dye from an aqueous stream, new polyaniline/multi walled carbon nanotube nanocomposites (PANI-MWCNTs) were applied as a promising photocatalyst. The PANI-MWCNT nanocomposites were fabricated by aniline oxidation in the presence of MWCNTs using the typical direct oxidation polymerization route. The morphology, the Fourier transform infrared (FTIR) spectra and the UV-Vis absorbance spectra of the fabricated nanocomposites were studied and the attained data confirmed the good interaction between the MWCNTs and PANI matrix. The PANI-MWCNTs nanocomposites were varied according to the wt%, the MWCNTs, which ranged from 0–10 wt% and the corresponding resultant samples are labeled as P-0, P-3, P-5, P-5, P-7 and P-10, respectively. Such composites showed the high potential for the removal of the Reactive Blue 4 dye containing pollutants from wastewater. The starting concentration of the dye pollutants was halved during the first 5 min of UV illumination. The oxidation technique of Reactive Blue 4 over the prepared nanocomposites were processed in a different way and the highest catalytic activity corresponded to P-7. The process reached the complete dye removal in low concentrations of contaminants. The kinetics of the removal followed the pseudo-second order regime which possesses high correlation coefficients with the k2 in the range of 0.0036–0.1115 L.mg−1.min−1 for the Reactive Blue 4 oxidation. In this regard, the combination of the PANI and MWCNTs showed a superior novel photocatalytic activity in the oxidation of commercial textile dying wastewater, namely Reactive Blue 4. This study is the starting point for future applications on an industrial scale since the successful performances of the PANI-MWCNT on commercial dye oxidation.

Application of emulsion liquid membrane for removal of malachite green dye from aqueous solution: Extraction and stability studies

Malachite green (MG) dye has various applications as a dyeing material, medical disinfectant and biocide but is also recognized as a teratogenic, carcinogenic, mutagenic and respiratory toxic material which creates dire effects on human beings, aquatic flora and fauna. Hence, the main objective lies in the removal of MG dye from an aqueous stream. In the current investigation, emulsion liquid membrane (ELM) technique was used and the effect of different factors like concentration of carrier, surfactant, stripping phase and its type and volume ratio of membrane to stripping solution on the removal of MG dye were studied. MG extraction efficiency of 94.99% was achieved using emulsion consisting of 2% w/v Span 80, 2% w/v D2EHPA, 0.1 N HCl and membrane phase to stripping phase volume ratio 1. Microscopic studies of the emulsion revealed the formation of well-defined and large number of globules with very less coalescence which resulted in high removal of MG dye. The physical stability of the emulsion was analysed and the phase separation was comparatively less at various time intervals suggesting that the conditions used for preparing the emulsions are suitable. Fourier transform infrared spectroscopy established the bonding and presence of various functional groups. The current study intends to fulfill the gap by exploring the removal of MG dye by ELM technique.

Encapsulation of Frankincense Essential Oil by Microfluidic and Bulk Approaches: A Comparative Study

Herbs and hand-made herbal remedies have been long used for disease control, treatment, and health improvement. Evidence suggests that a single herb’s compounds can have synergistic functions with probably no adverse effect. Unfortunately, the traditional administration of essential oil (EO) does not follow a regulatory dose regimen, causing reduced bioavailability due to EO evaporation or denaturation in harsh biological environments. Hence, encapsulation can help enhance EO stability and dose dependence. Here, chitosan nanoparticles (ChNPs) were used to encapsulate frankincense essential oil (FEO) to preserve its remarkable therapeutic effects. Also, traditional bulk preparation methods were compared with microfluidic with central aqueous stream configuration (CAS). The results indicated the higher quality of microfluidic-based nanoparticles with uniform, spherical, and separated morphologies. The size of bulk and microfluidic nanoparticles ranged from 86 to 118 nm, the surface charge varied from 12.5 to 19.5 for different amounts of FEO, and the as-prepared colloid remained stable for three days. Narrow size distribution (PDI≤0.28) and high encapsulation efficiency (EE≤99 %) were achieved using the microfluidic process compared to the bulk method (PDI=0.74, EE≤90 %). The microfluidic nanoparticle also indicated a burst release rate greater than the bulk method (≤30 %). It was concluded that the high-performance microfluidic approach provided higher quality and more control over nanoparticle properties.

Extracting extremophilic lipases from aqueous streams by using biocompatible ionic liquids

In this work, biocompatible ionic liquids based on aminoacids were employed as extractants to separate extremolipases from aqueous streams. First, the influence of aminoacid and dipeptide-based ionic liquids (cholinium glycinate, ChGly, and cholinium glycylglycinate, ChGlygly) on the lipolytic activity of a commercial lipase from Candida antarctica (CaLB) and in-house synthesized extremophilic lipases from Thermus thermophilus HB27 (TtHB27L) and Halomonas sp. LM1C (HL) was investigated. The combination of thermophilic enzyme with ChGly turned out to be the optimum combination for maximizing the biocatalytic performance, clearly improving the levels attained when water was exclusively employed as solvent and also surpassing the activity levels provided for the commercial enzyme CaLB. The salting out capacity of ChGly in aqueous solutions of biodegradable surfactants Tergitol 15S7 and Tergitol 15S9 was discussed, recording immiscibility areas almost covering all the ternary diagrams. The aqueous biphasic systems were experimentally characterized by determining both tie-lines and solubility curves at several temperatures and the data was modelled with relevant equations like Merchuk, Othmer-Tobias and Bancroft ones, as they are the most common ones to describe this kind of equilibrium data. So, ChGly was applied to extract thermophilic and commercial lipases from aqueous solutions at 313.15 K, achieving very high extraction levels (about 100 %) for TtHB27L, which clearly surpasses the maximum extraction values observed for the commercial enzyme (about 80 %). Finally, the process was simulated at real scale through SuperPro Designer v.8.5 for the production of 385 Kg/year of extremolipase.

Vegetable Oil-Ionic Liquid-Based Emulsion Liquid Membrane for the Removal of Lactic Acid from Aqueous Streams: Emulsion Size, Membrane Breakage, and Stability Study.

In this study, we present a highly stable vegetable oil ionic liquid (IL)-based emulsion liquid membrane (VOILELM) for the removal of lactic acid from water streams. The system developed as a part of this work comprises a non-ionic surfactant Span 80, sodium hydroxide as an internal stripping agent, sunflower canola oil as a green diluent, and IL—tetramethylammonium acetate [TMAm][Ac]—as a carrier. VOILELM stability was evaluated in terms of breakage, emulsion diameter, and standalone stability. The effect of various parameters, namely, concentration of the surfactant, concentration of the internal stripping agent, concentration of the carrier, phase ratio, homogenizer speed, and homogenization time, on the VOILELM stability was studied. The results revealed that VOILELM was highly stable, with 1.34% minimum breakage, 1.16 μm emulsion diameter, and 131 min standalone stability. The optimal process parameters were 0.1 wt % Span 80, 0.1 M NaOH, 0.3 wt % IL, 0.25 phase ratio, 5000 rpm homogenizer speed, and 5 min homogenization time. At these optimized conditions, 96.08% lactic acid extraction efficiency was achieved. Thus, a highly effective VOILELM was developed, with minimal breakage and emulsion diameter and maximum stability.

Localized Heating to Improve the Thermal Efficiency of Membrane Distillation Systems

Membrane distillation (MD) is a thermal-based membrane operation with high potential for the treatment of aqueous streams. However, its implementation is limited and only few examples of MD pilots can be found in desalination. One of the reasons behind this is that MD requires thermal energy for promoting the evaporation of water, which implies higher energy consumption with respect to pressure-driven membrane operations, like reverse osmosis (RO). Recently, among the different methods investigated to improve the thermal efficiency of MD, attempts for obtaining a localized heating of the feed, close to the membrane surface, were carried out. This work reviews experimental activities on the topic, dealing with both modified membranes, used under solar irradiation or coupled to an electric source, and specifically designed heated modules. The main results are reported and points of action for further optimization are identified. In particular, although at an early stage, this type of approach led to improvements in membrane flux and to a reduction of energy consumption with respect to conventional MD. Nevertheless, long tests to ensure a stable performance time, the optimization of operating conditions, the development of methods to control fouling issues, and the identification of the best module design, together with the scale-up of membranes/modules developed, represent the main research efforts needed for future implementation of localized heating strategy.

Laboratory- to Pilot-Scale Fractionation of Lignocellulosic Biomass Using an Acetone Organosolv Process

Acetone organosolv fractionation of beech and birch wood at the lab-scale results in high sugar yields from the (hemi)cellulose and the isolation of a high-purity lignin. In this study, the process is scaled up to validate the technology at the pilot scale using industrial-size beech and birch wood chips and low liquid-to-solid ratios as a next step toward commercialization. Translation of the fractionation process to the pilot-scale showed a similar performance as compared to the lab-scale processing with a good conversion of the wood polymeric pentoses to mostly monomeric sugars and a high delignification. Continuous lignin precipitation by solvent evaporation using the LigniSep process resulted in the formation of nonsticky lignin aggregates with a good filterability. The improved lignin yields and advanced process design as compared to the traditional dilutive lignin precipitation approaches are likely to translate to a better process economy. The pulp washing efficiency and the recovery of (nonprecipitable) lignin from the aqueous hemicellulose stream still need to be improved for an efficient process design. However, the fractionation performance and high product concentrations in the spent liquor provide an excellent start position for improved process design at the commercial scale.

Compendium data and preliminary results based on alum sludge and gravel continuous fixed-packed-bed column substrate as sustainable practice for constructed wetland development in northern Egypt

The present investigation represents the valuable reclaims of the aluminum-based waterworks sludge that is so called “alum sludge” to close the loop concerning the sludge waste production and the sustainable ecosystem. In this study the adsorption behaviors of aluminium based sludge, namely alum sludge (AS) and gravel as cost-efficient adsorbents regarding dye elimination from aqueous synthetic stream were analyzed in fixed bed column. The influence of variable boundaries such as column pack depth and influent concentration on the effluent concentrations via breakthrough curves were examined. It is estimated that the removal uptake and sorption capabilities elevated as the initial influent loading of the dye dismissed for the fixed bed height of the both adsorbents, namely, gravel and AS. Thereafter, a preliminarily results were checked to investigate the feasibility of the adsorption column in Reactive Blue 4 (RB4) adsorption. The maximum adsorption capacities were observed around 4 mg L-1 for sample with pH 7.5 that is signified as the natural pH of the synthetic stream. However, increasing the initial dye loading increasing the adsorption capacity which reached to 5.5 mg L-1 for the dye loading 27.8 mg L-$$$1 of Reactive Blue 4 (RB4). Thus, the first results will be a valued scheme in the development of adsorption systems to build up a constructed wetland facility.

Reactive extraction of caproic acid using tri n-octylamine + 2 octanol system

Recovery of dilute caproic acid from waste streams by reactive extraction using tri n-octyl amine (TOA) as an extractant and 2 octanol as a diluent is attempted in this work. 0.005–0.0572 mol/lit concentration of caproic acid found in aqueous streams of fermentation broth is left untreated or found too expensive to recover by conventional methods. Reactive extraction is an intensified technology implemented for maximum recovery of acid. An identical concentration range of caproic acid was used for batch experiments using toluene, benzyl alcohol, 2 octanol, and decanol as diluents in independent experimental runs. A comparative experimental study was made by adding TOA as an extractant. The results revealed 2 octanol to be the suitable diluent among selected diluents for extraction of very dilute acid concentrations of 0.005 mol/lit. Hence, 2 octanol was selected for further study of reactive extraction experiments. Nearly 54–87 % degree of extraction was observed in physical extraction when 2 octanol alone was used as a diluent. However, reactive extraction using TOA in 2 octanol exhibited a synergetic effect on the recovery of the acid. The degree of extraction enhanced nearly by 30% and is reported in the range 86 to 98.60 % whereas the distribution coefficient is in the range 6.5–67. Encouraging results were achieved in a continuous counter-current extraction experiment, extraction efficiency was found to be 91% for very dilute acid (0.005 mol/lit). The novelty of the work is in exploring the TOA + 2 octanol system for extraction of caproic acid in batch and continuous mode of operation. Experimental work on reactive extraction of carboxylic acid using counter-current packed column is rarely reported and hence we have explored this technology in a continuous mode of operation.

Development of an aqueous lignin mixture thermophysical model for hydrothermal liquefaction applications using uncertainty quantification tools

A thermophysical model is developed that can predict the properties of two lignin mixtures, black liquor and lignosulfonates, up to 50% mass fractions, at hydrothermal conditions. An uncertainty quantification framework linked with classic thermodynamical modelling was included to account for the extreme variability of the raw material. An idealised flow simulation verified the model, where hot compressed water mixes with a cold, aqueous lignin stream in a T-piece reactor configuration. The uncertainty quantification procedure determined that density and heat capacity uncertainty significantly influence residence time, and viscosity uncertainty mainly affects mixing. Micromixing time is fivefold and ten-fold higher for black liquor and lignosulfonates mixtures, respectively, compared to pure water mixing. The uncertainty in all simulated quantities of interest caused by the thermophysical model is reduced by increasing flow rates. This study predicted chemical reactor behaviour under varying thermophysical conditions and their final effect in terms of confidence intervals.

Experimental investigation on recovery of bio‐based protocatechuic acid using ionic liquids

AbstractBACKGROUNDThe production of protocatechuic acid (PCA) (which has significant applications in organic intermediates, chemical reagents, pharmaceuticals, dye synthesis, etc.) by fermentation is a potential replacement to the conventional petrochemical routes of carboxylic acid production. However, the extraction processes of these carboxylic acids from fermentation broths and dilute waste water using organic solvents imply additional environment hazards. Ionic liquids (ILs) have come to the focus because of their superior properties as well as environmentally friendly nature, and are being intensively used for separation processes. The equilibrium extraction efficiency for bio PCA using two imidazolium ILs – 1‐butyl‐3‐methylimidazolium tetrafluoroborate (bmimBF4) and 1‐butyl‐3‐methylimidazolium hexafluorophosphate (bmim‐PF6) – was investigated under isothermal conditions in diluent octanol. The distribution coefficient and extraction efficiency were determined to be much greater than those obtained with traditional extractants and diluents.RESULTSThis work is the first of its type to use ILs for PCA isolation. From the equilibrium extraction experiments conducted it was observed, in octanol, that the average distribution coefficients (KD) values for bmimBF4 and bmim‐PF6 were 5.3 and 5.36, respectively, with average extraction efficiencies of 83.84% and 84.08% at a lower IL concentration of 10% by volume, and the findings may be utilised to develop an extraction purification system for PCA separation from aqueous streams. Multiple stages of separation may lead to almost 100% recovery.CONCLUSIONPCA was efficiently extracted from aqueous solutions using bmimBF4 and bmim‐PF6 in octanol, providing preliminary practical information and theoretical support for PCA separation, purification and recovery. © 2022 Society of Chemical Industry (SCI).

Aquananotechnology: oriented-sawdust waste valorization into magnetic nanocellulosic particles for Synozol Red K-HL sorption prospect

High loaded textile dying effluents should undergo for treatment prior to final disposal into the environment. The current study aimed to apply naturally abundant and cheap by-product material namely sawdust (SWD) to develop magnetized cellulosic nano-adsorbent based on magnetite nanoparticles for reactive dye removal namely Synozol Red K-HL (R K-HL). The powder of SWD, which is available through various industries, was modified via pre-treatment with acid hydrolysis and bleaching before blending them with magnetite particles which is synthesized via co-precipitation route. Sawdust (SWD) conjugated with Fe3O4 at different weight percentages (wt%), i.e. SF-(1:1), SF-(2:1), SF-(3:1), SF-(5:1) and SF-(1:2), then subjected to microwave technique, and then characterized by X-ray diffraction spectroscopy (XRD); transmission electron microscope (TEM); Fourier transform infrared (FTIR). Thereafter, the effects of system parameters on adsorption capability, i.e. pH, temperature and dye loading were studied using the modified adsorbents. The SF-(2:1) adsorbent showed the highest affectivity which achieved the highest (21.71 mg g−1) adsorption uptake with a catalyst dosage of 1 g L−1. Moreover, a complete dye removal (100%) was attained at low initial dye loading in the aqueous medium. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D-R) isotherm models and their corresponding constants were calculated and discussed. The experimental results showed that the Langmuir isotherm model is well expressed in the experimental data. The kinetics of R K-HL dye removal was found to depend on operational temperature. A study of three kinetic models has been made, and the Bangham’s kinetic model was found to describe the adsorption of dye R K-HL on all the adsorbents applied. The adsorption of reactive R K-HL onto magnetized sawdust adsorbents was spontaneous and exothermic in nature as concluded from thermodynamic assays. Experimental results verified that dye R K-HL could be successfully eliminated feasibly from the aqueous stream in economic way.

A pathway to improve detoxification processes by selective extraction of phenols and sugars from aqueous media using sustainable solvents

Integrated biorefineries are the current trend to produce energy, biochemicals and biofuels. A variety of sugar-rich biorefinery streams can be further valorized by fermentation but the presence of inhibitory compounds hinders the fermentation yields. This paper proposes a detoxification method by selective liquid extraction of phenolic compounds using sustainable solvents to improve the fermentation of sugar-rich aqueous streams. Specifically, three hydrophobic eutectic solvents constituted by binary mixtures of octanoic, decanoic or dodecanoic acid (octanoic: decanoic acid 1:1, octanoic: dodecanoic acid 3:1, decanoic: dodecanoic acid 2:1) and three bio-based solvents (2-methyltetrahydrofuran, cyclopentyl methyl ether and limonene) were selected to analyze their capacity to extract representative phenolic compounds (phenol, o-cresol, guaiacol, syringol and vanillin) from aqueous solutions. Extraction efficiencies of individual compounds and mixtures of them were evaluated at different concentrations and temperatures using the proposed solvents. Finally, the liquid extraction of a solution containing 500 mg/L of phenolic compounds and 50 g/L of glucose, as a representative concentration in biorefinery streams, was performed. The distribution of the target compounds in each phase after the extraction process was analyzed by HPLC-DAD in the case of phenolic compounds and HPLC-RI for glucose, and discussed in terms of selectivity. The results obtained are very promising, as the studied solvents can easily extract phenolic compounds but not glucose, which could improve the subsequent sugar fermentation process. In particular, the bio-based solvent cyclopentyl methyl ether provided extraction efficiencies of phenolic compounds above 93%, while that of glucose remained lower than 4%. Finally, all the experimental results were analyzed by means of COSMO-RS methodology, obtaining reliable trends and concluding that the ability of the solvents to form hydrogen bonds with phenolic compounds determines the extraction efficiencies.