Solution pH Research Articles

Investigating the Formation of Polymer-Nanoparticle Complex Coacervate Hydrogels Using Polymerization-Induced Self-Assembly-Derived Nanogels with a Succinate-Functional Core.

This paper reports polymer-nanoparticle-based complex coacervate (PNCC) hydrogels prepared by mixing anionic nanogels synthesized by polymerization-induced self-assembly (PISA) and cationic branched poly(ethylenimine) (bPEI). Specifically, poly(3-sulfopropyl methacrylate)58-b-poly(2-(methacryloyloxy)ethyl succinate)500 (PKSPMA58-PMES500) nanogels were prepared by reversible addition-fragmentation chain-transfer (RAFT)-mediated PISA. These nanogels swell on increasing the solution pH and form free-standing hydrogels at 20% w/w and pH ≥ 7.5. However, the addition of bPEI significantly improves the gel properties through the formation of PNCCs. Diluted bPEI/nanoparticle mixtures were analyzed by dynamic light scattering (DLS) and aqueous electrophoresis to examine the mechanism of PNCC formation. The influence of pH and the bPEI-to-nanogel mass ratio (MR) on the formation of these PNCC hydrogels was subsequently investigated. A maximum gel strength of 1300 Pa was obtained for 20% w/w bPEI/PKSPMA58-PMES500 PNCC hydrogels prepared at pH 9 with an MR of 0.1, and shear-thinning behavior was observed in all cases. After the removal of shear, these PNCC gels recovered rapidly, with the recovery efficiency being pH-dependent.

Aging Ni(OH)2 on 3C-SiC Photoanodes to Achieve a High Photovoltage of 1.1 V and Enhanced Stability for Solar Water Splitting in Strongly Alkaline Solutions.

Photoelectrochemical (PEC) water splitting is a promising approach to directly convert solar energy to renewable and storable hydrogen. However, the very low photovoltage and serious corrosion of semiconductor photoelectrodes in strongly acidic or alkaline electrolytes needed for water splitting severely impede the practical application of this technology. In this work, we demonstrate a facile approach to fabricate a high-photovoltage, stable photoanode by depositing Ni(OH)2 cocatalyst on cubic silicon carbide (3C-SiC), followed by aging in 1.0 M NaOH at room temperature for 40 h without applying electrochemical bias. The aged 3C-SiC/Ni(OH)2 photoanode achieves a record-high photovoltage of 1.10 V, an ultralow onset potential of 0.10 V vs the reversible hydrogen electrode, and enhanced stability for PEC water splitting in the strongly alkaline solution (pH = 13.6). This aged photoanode also exhibits excellent in-air stability, demonstrating identical PEC water-splitting performance for more than 400 days. We find that the aged Ni(OH)2 dramatically promotes the hole transport at the photoanode/electrolyte interface, thus significantly enhancing the photovoltage and overall PEC performance. Furthermore, the oxygen evolution reaction (OER) activity and the phase transitions of the Ni(OH)2 electrocatalyst before and after aging are systematically investigated. We find that the aging process is critical for the formation of the relatively stable and highly active Fe-doped β-NiOOH, which accounts for the enhanced OER activity and stability of the PEC water splitting. This work provides a simple and effective approach to fabricate high-photovoltage and stable photoanodes, bringing new premise toward solar fuel development.

Efficient removal of Cr(VI) containing tunnel wastewater by sludge biochar loaded with ferrous sulfate

The ease of agglomeration reduced the removal of pollutants by FeS particles. Hence, sludge biochar was employed as a support to produce FeS-loaded biochar composites (FeS@BC) using a solvothermal method, for removing Cr(VI) from wastewater. The performance and mechanism of Cr(VI) removal on FeS@BC were investigated through adsorption experiments and characterization techniques. The adsorption tests revealed that under optimal conditions of solution pH of 3 and dosage of 40 mg, FeS@BC achieved a removal efficiency of over 97 % for 50 mg/L Cr(VI). The presence of Cl- and NO-3 did not affect Cr(VI) removal, whereas sulfate, phosphate, and carbonate inhibited the removal process. Low concentrations of humic acid (1–5 mg/L) held a negligible influence on removing, but elevated concentrations of humic acid inhibited Cr(VI) removal. The behavior of FeS@BC in removing Cr(VI) complied with to the pseudo-second-order and the Langmuir model. At 308.15 K, the largest removal capability of FeS@BC for Cr(VI) reached 185.874 mg/g. Thermodynamic studies confirmed that the Cr(VI) removing processes on FeS@BC were a spontaneous, entropy-driven, endothermic chemical adsorption. The primary mechanism for removing Cr(VI) on FeS@BC included reduction, electrostatic adsorption, complexation, and precipitation, with the reduction process playing a crucial role. This indicated that sludge biochar loaded with FeS was an ideal material for removing Cr(VI) from wastewater.

Investigation on novel chitin and chitosan from dung beetle Heteronitis castelnaui (Harold, 1865) and its potential application for organic dyes removal from aqueous solution

Chitosan, a natural polysaccharide, has attracted considerable attention as an environmentally friendly and highly efficient adsorbent for dye removal. It is usually produced by deacetylation or partial deacetylation of chitin. However, conventional sources of chitin and chitosan are limited, prompting the need for alternative sources with improved adsorption capabilities. Herein, this study focuses on exploring a novel chitin and chitosan source derived from the dung beetle and evaluates its potential for organic dye removal from aqueous solutions. The research involves the extraction and characterization of chitin and chitosan from dung beetle Heteronitis castelnaui (Harold, 1865) using various analytical techniques, including SEM, FT-IR, TGA, XRD, NMR, deacetylation degree and elemental analysis. The chitosan obtained was used for the formation of hydrogels with sodium alginate via cross-linking with calcium chloride. And then the prepared hydrogels were evaluated for its adsorption capacity through batch adsorption experiments using methylene blue as a model pollutant. The adsorption capacity for methylene blue was 1294.3 mg/g at room temperature with solution pH = 12, MB concentration of 1800 mg/L. Furthermore, the kinetics of the adsorption process were analyzed using pseudo-first-order and pseudo-second-order models to understand the rate of adsorption. The maximum adsorption capacities were determined using Langmuir and Freundlich isotherm models. This study provides valuable insights for the development of sustainable dye adsorption technologies, specifically investigating a novel chitosan source derived from the dung beetle.

Effect of Non-Essential Alloying Elements and Solution pH on Corrosion Behavior of Al-Mg Alloys Fabricated by Cold Spray Deposition

ABSTRACT This paper highlights the difference in corrosion behavior of cold spray (CS) deposited AA5083 and Al-5.0 wt.% Mg alloys with an emphasis on the effect of non-essential alloying elements and solution pH. CS process is an emerging technology to repair damaged structures via solid-state deposition. While recent works have focused on CS Al alloys, less attention has been paid to CS Al binary alloys in comparison to Al engineering alloys, which have important implications for the integrity of structural components repaired by the CS process. Herein, the microstructure of CS AA5083 and Al-5.0 wt.% Mg binary alloy was analyzed by various microstructure characterization techniques. Corrosion behavior was assessed using electrochemical and immersion tests in 0.6 M NaCl (pH 8.3 and 11.5) solution. Intermetallic phases, such as Fe- and Si-containing phases, in CS AA5083 decreased corrosion resistance by increasing cathodic kinetics in near-neutral solution. In addition, immersion tests demonstrated lower corrosion resistance in CS AA5083 than in CS Al-5.0 wt.% Mg whereas an alkaline environment showed the presence of a secondary passive layer on CS AA5083, providing higher corrosion resistance compared to CS Al-5.0 wt.% Mg.

Efficient sorption and secure immobilization of strontium ions onto nanoporous alumino-borosilicate as a new matrix

The objective behind developing the nanoporous alumino-borosilicate (AlBS) was to remove strontium ion (Sr2+) from liquid waste and subsequently stabilize it. The sorption capacity of the nanoporous AlBS was assessed in relation to various experimental factors, including contact time, temperature, initial pH solution, and initial concentration of Sr ions. According to the obtained results, nanoporous AlBS shows a maximum Sr2+ sorption capacity of 163.08 mg/g. In order to achieve stable immobilization of the sorbed Sr ions, heat treatments at different temperatures were applied to the Sr-containing nanoporous AlBS. Various eluents were used in the leach tests to examine the Sr ions leaching from heat-treated materials. Only 3.43% of the Sr ions initially adsorbed in the nanoporous AlBS matrix was washed out with 1 M sodium chloride eluent, showing that heating the sample to around 1100 °C successfully trapped Sr ions in the nanoporous AlBS matrix.

Optimized Lithium(I) Recovery from Geothermal Brine of Germencik, Türkiye, Utilizing an Aminomethyl phosphonic Acid Chelating Resin

ABSTRACT This study investigates the performance of Lewatit TP 260 ion exchange resin for the efficient recovery of lithium (Li(I)) from geothermal water sourced from the Germencik Geothermal Power Plant in Türkiye. A series of batch sorption experiments were performed to evaluate the influence of key parameters, including resin dosage, solution pH, temperature, initial Li(I) concentration, and contact time, on the Li(I) recovery process. The optimal conditions were determined to be a resin dose of 0.5 g per 25 mL of geothermal water, pH in the range of 6–8, and a temperature of 25°C. Under these conditions, the resin achieved a maximum Li(I) recovery rate of 71% from the geothermal water. Sorption isotherms were further analyzed using the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) models. Among these, the Langmuir model provided the best fit (R² = 0.9841), suggesting a maximum sorption capacity (qm) of 4.31 mg/g. Continuous recovery experiments conducted in column mode confirmed the practical applicability of Lewatit TP 260, achieving a total sorption capacity of 0.41 mg Li(I)/mL resin. The findings exhibit the potential of this resin as a viable sorbent for sustainable Li(I) extraction from geothermal brines, supporting the development of green energy technologies and contributing to the circular economy.

Transformation of waste thermocol into activated carbon for electrochemical detection of ammonia in an aqueous solution

In this study, waste thermocol sheets are used to synthesize activated carbon (AC) for the electrochemical detection of ammonia in an aqueous solution. The AC is characterized for its morphology, structure, and chemical composition via standard characterization techniques. AC shows promise for detecting ammonia in aqueous solutions due to its high adsorption capacity from large surface area and porosity. The electrochemical approach used to detect ammonia (NH3) in electrolyte solutions uses an AC electrode and is based mostly on the electro-oxidative conversion of ammonia species at the electrode's interface. AC electrodes fabricated on flexible conductive fabric (CF) are used for the electrochemical detection of ammonia at pH 6. The electrochemical sensing of ammonia in aqueous solutions involves its oxidation on the electrode's surface. Cyclic Voltammetry (CV) experiments were conducted over a pH range of 5 to 8, revealing optimal current responses at pH 6. Therefore, phosphate-buffered saline (PBS) at pH 6.0 was employed for all electrochemical analyses. Various concentrations of ammonia (10–100 ppm) were investigated within a voltage window of −0.3 V to 0.3 V, with current signals increasing proportionally with ammonia concentration. The limits of detection (LOD) and quantification (LOQ) were determined to be 28.55 ppm and 86.54 ppm, respectively. An incubation period of 3 min was observed for ammonia concentrations ranging from 0 to 40 ppm. Selectivity evaluations were conducted by assessing interference effects from ethanol (E), methanol (M), toluene (T), and uric acid (UA), revealing ammonia's distinctive peak, indicative of superior selectivity. Notably, the electrode exhibited remarkable stability, retaining approximately 95 % of the original signal over a 5-week duration. The reproducibility of the fabricated electrodes shows significant results. The repeatability was performed at room temperature in a buffer solution of pH 6 and at a 40-ppm concentration of ammonia and has shown almost similar results. Therefore, the fabricated AC sensing electrode has shown prominent stability, reproducibility, and repeatability. These sensing electrodes can be very beneficial for sensing applications.

Probing the Interfacial Interaction Mechanisms of Nitrogen with Dodecane/Toluene: Implications for Foam Flooding.

Interfacial interactions between deformable bubbles and oil drops have attracted much attention in foam flooding. However, interactions involving nitrogen bubbles have not been reported. In this work, the interaction forces between nitrogen and dodecane/toluene in aqueous solutions were quantified using the atomic force microscopy bubble probe technique. The effects of the solution pH, ionic type, and solution concentration on the interactions were analyzed. The van der Waals (vdW), electric double layer (EDL), and hydrophobic (HB) interactions were involved in the low-concentration solutions. The EDL repulsion in NaCl increased with solution pH, while in CaCl2 and MgCl2, the EDL repulsion in general decreased and then increased with pH, attributed to the adsorption of OH- and divalent cations and their hydration products. The adsorption of divalent cations at the toluene/water interface was pronounced by cation-π interactions. At pH 10, precipitated divalent cation hydroxides at the bubble/water and oil/water interfaces adsorbed more cations, causing the increase of the surface potential. At high salinity, the EDL interaction was suppressed and the vdW repulsion became predominant. The vdW force of nitrogen with toluene was stronger than that with dodecane. Under all of the solution conditions, the attractive interaction could not overcome the total repulsive interaction at the minimum separation, and thus no bubble attachment was observed, which implied that a stable bubble/liquid/oil film was essential for maintaining foam stability. This work provides useful insights into the interfacial interaction mechanisms in nitrogen foam flooding. The findings can be readily extended to other engineering systems such as oil flotation and bubble-oil-water emulsions.

A time-resolved investigation at multiple-length scales of the structure of liquid foam stabilized by albumins from pea

HypothesisThe structural details of foams made with pea albumins are affected by the pH of the initial solution and followed heat treatment. ExperimentsAn in situ, time-resolved investigation of foams prepared with pea albumins was conducted using small-angle neutron scattering (SANS) in combination with imaging and conductance measurements. Solutions were tested at pH three pH values (3, 4.5, and 8) before and after heating (90 °C for 1 and 5 min). FindingsThe characteristic structures present in the foam from the nano to the meso-scale differed during drainage depending on solution pH. Foams obtained at pH 3, had the largest bubble radius and thinnest plateau border, as well as the highest extent of liquid drainage. At pH 4.5, close to the isoelectric point of the proteins, foams displayed similar bubbles’ behavior to those at pH 8, but with the largest film thickness. In this case, the proteins were extensively aggregated. Heating of the solutions prior to foaming did not significantly affect the foam aging regardless of pH. The quantification of specific surface areas and film thickness over time without sample disruption shows to be a powerful approach to designing foam structures.

Effect of morphology on the optical limiting of BiVO4 films

Precise control over the morphology and crystal structure of semiconductor-based optical materials is essential for optimizing their nonlinear optical properties. Morphological factors significantly affect the material’s interaction with light, influencing nonlinear absorption, harmonic generation, and optical confinement. In this study, the nonlinear optical (NLO) properties and optical limiting (OL) performance of bismuth vanadate (BiVO4) films depending on precursor solution pH condition, powder morphology and weight percentage of the BiVO4 powders in PMMA (10–30 wt.%) were investigated. The BiVO4 powders were synthesized via the hydrothermal method and the effect of precursor solution pH (pH of 1, 7.5 and 12) was investigated on the size and morphology of the BiVO4 powders. BiVO4 films were prepared using the spin coating method utilizing the BiVO4 powders and PMMA. The bandgap values of films were found to change from 3.39 to 3.56 eV depending on the BiVO4 growth solution pH. The nonlinear absorption coefficients (βeff), saturation intensity thresholds (ISAT) and optical limiting (OL) threshold were obtained using the open aperture (OA) Z-scan experiment. It has been observed that the nonlinear absorption and optical limitation performance of the BiVO4 films can be altered by changing the powder morphology and BiVO4 weight concentration. BiVO4 thin films fabricated using a precursor solution pH 12 and weight concentration of 30 wt.% showed the best performance among all fabricated films with the highest nonlinear absorption coefficient (βeff), saturation density threshold (ISAT) and lowest OL threshold value.

400 Effect of pH on in vitro ruminal metabolism of trans-10 18:1 and trans-11 18:1

Abstract Dietary C18 unsaturated fatty acids are extensively biohydrogenated by rumen microbiota into 18:0 and trans-18:1 isomers. Usually, the biohydrogenation (BH) pathways produce mostly 18:0 and trans-11 18:1 as the main intermediate. However, when fed low-forage diets that decrease the rumen pH, the main BH intermediate often is the trans-10 18:1 isomer. This change in BH, called the trans-10 shift, is associated with milk fat depression, but despite that, little is known about the triggers of the trans-10 shift and its ecological role in rumen microbiota. Microbiota stressed by low rumen pH may benefit from increased trans-18:1 availability favoring the production of the trans-18:1 isomer with a slower rate of BH. Thus, we hypothesize that at low rumen pH conditions, the BH of trans-10 18:1 will be slower than that of trans-11 18:1. We tested that with an in vitro experiment using batch incubation in Hungate tubes, replicated in 5 wk. In each run, 24 tubes were allocated at 6 treatments and 4 incubation times (0, 6, 24 and 48 h). The treatments resulted from the combination of 2 buffering solution pH (6.74 vs. 5.85) and 3 substrates: 1) Control (60 mg feed DM) 2) T10 (Control plus 1.2 mg of trans-10 18:1) and 3) T11 (Control plus 1.2 mg of trans-11 18:1). Volatile fatty acids (VFA) and long-chain fatty acids were analyzed by gas chromatography. Data were analyzed using the 2 × 3 factorial arrangement for each incubation time. Low pH resulted in less 30 to 37% DM disappearance than those with high pH at all incubation times (P < 0.05). The decrease in VFA with low pH was less expressive (≈17%) and only evident at 24 and 48 h incubation times. The low pH also decreased (P < 0.05) the BH of 18:1n-9 (less ≈47 to 53%), 18:2n-6 (less 30 to 34%) and 18:3n-3 (less 20 to 22%) at 24h and 48h incubation times, respectively. The disappearance of trans-11 18:1 was 14.6% at 6 h, 29.0% at 24 h and 32.8% at 48 h and was not affected by pH. The disappearance of trans-10 18:1 was dependent on pH. At 6 h and high pH the disappearance of both was similar, but at low pH the disappearance of trans-10 18:1 was much less (9.8%) than that of trans-11 18:1. However, at 48 h and low pH, the disappearance was similar between isomers and the disappearance of trans-10 18:1 was much greater (46.6%) than trans-11 18:1. In summary, the BH of trans-10 18:1 is less at low pH than at high pH, and this could in part explain its abundance in some practical ruminant feeding conditions. Acknowledgements: Fundação para a Ciência e a Tecnologia (FCT) funding through PTDC/CAL-ZOO/29654/2017(RumOmics), PTDC/CAL-ZOO/4515/2021(Gene2Rumen), UIDB/00276/2020 (CIISA), and LA/P/0059/2020 (AL4Animals) projects.

Spectrophotometric determination for green hydrophobic deep eutectic solvent-based microextraction of Brilliant Blue FCF (E133) from beverages

In this study, a simple, sensitive, and rapid method called green hydrophobic deep eutectic solvent-based liquid-liquid microextraction was developed to extract Brilliant Blue FCF dye from beverages. This method utilizes hydrophobic DES obtained by forming tetrabutylammonium bromide and 1-octanol in a 1:5 ratio as green extraction solvent. The transition of Brilliant Blue FCF to the DES phase occurred on its own, without the need for any reagents such as added salt or tetrahydrofuran. Several crucial factors were tried to get the best extraction efficiency, including species, DES volume and molar ratio, solution pH, ultrasonication, and centrifugation time. Under optimum conditions, extraction recoveries were achieved in the range of 95.1–101.3 % with the method developed for Brilliant Blue FCF. The detection and determination limits were observed to be 4.1 μg l-1 and 12.1 μg l-1, respectively. In addition, the relative standard deviation values for the method's accuracy were found to be 2.23 % and 3.48 % within and between days, respectively. It has been established that the developed method is highly environmentally friendly thanks to the application of the Analytical GREENness (AGREE) and Green Analytical Procedure Index (GAPI) tools. This study shows that DES applications can be carried out without the use of emulsifiers and dispersants by prioritizing the use of hydrophobic DES compounds as environmentally friendly and green extraction solvents in food samples.

Multivariate calibration in smartphones using digital images for the determination of pH of drinking water

The execution of calibration models was previously restricted to computers, but with technological advances, applications on mobile devices have made this process more accessible. Photometrix PRO stands out as an innovative tool for creating calibration models from digital images. The colorimetric chart, widely used to determine the pH of solutions by visual analysis, can present subjectivity in interpretation. This study aims to develop and evaluate calibration models (PLS) using Photometrix PRO to accurately correlate the visual information of a colorimetric pH chart from the company AlfaKit. The application was used to acquire images, generate calibration curves and obtain pH values from prediction and validation sets. The curves presented R2, RMSEC and RMSECV that indicated good fit of the models. The t-test, with 95% confidence, showed that there was no significant difference between the results of the models and the colorimetric method. The Residual Prediction Deviation (RPD) ranged from 1.12 (RGB) to 5.37 (RGBHSVLI), making the model (RGBHSVLI) suitable for quality control. The study successfully demonstrated the feasibility and effectiveness of smartphone-based multivariate calibration (PLS) for determining pH in drinking water.

Ultrahigh-purity ammonia recovery from synthetic coke wastewater via membrane contactor: Overcoming phenolic interference and assessing cost efficiency

Ammonia recovery from industrial wastewater using membrane contactor processes is emerging as a promising method owing to the diverse applications of ammonia. This study uniquely addressed ammonia recovery from coke plant wastewater, which is challenging due to the presence of numerous toxic and volatile phenolic compounds. Experiments were conducted using a synthetic coke plant effluent to assess the effects of various pH levels and temperatures on ammonia recovery. Specifically, the aim was to achieve high-purity ammonia recovery while minimizing the permeation of phenolic compounds. The results demonstrate that ammonia recovery in the membrane contactor processes is highly efficient, even in the presence of phenolic compounds. During temperature variations at 25 °C and 40 °C, the recovery of ammonia increased from 42.36% to 52.97% at pH 11. Additionally, increasing the pH of a feed solution from 7 to 12 significantly increased the ammonia content to 58.3%. At this pH, the recovered ammonia was of exceptional purity (>99%), with phenol, p-Cresol, and 2,4-xylenol present at negligible concentrations (0.001%, 0.002%, and 0.004%, respectively). This was attributed to the ionization of phenolic compounds at higher pH levels, which prevents their permeation through the hydrophobic membrane. The estimated cost analysis revealed that the membrane contactor process at pH 12 was approximately 1.41 times more cost-effective than conventional air-stripping processes over eight years of operating period (pH-12 membrane contactor: $19.79; pH-12 air stripping: $23.75). This study provides a detailed analysis of the optimal conditions for selective ammonia recovery from complex wastewater, highlighting both effective treatment and sustainable resource recovery and offering a superior alternative to traditional methods.

Efficient separation of HEPES and CO2-derived fructose by nanofiltration: Optimizing pH for improved separation and proposing a potential mechanism

Utilization of an in vitro multi-enzyme catalytic system for the synthesis of fructose from carbon dioxide is a promising approach towards achieving carbon neutrality. However, the lack of effective separation methods for the buffer HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) and the product fructose within the system has hindered the industrialization of in vitro multi-enzyme catalytic synthesis systems. This study aimed to separate and recover HEPES and fructose using nanofiltration technology. We investigated the influence of various parameters, including total solution concentration, solute concentration ratio, pH, and temperature, on the nanofiltration separation performance. Experimental results revealed that increasing the pH to 9.0 significantly decreased the fructose retention rate while maintaining a nearly complete HEPES retention rate. The HEPES-fructose mixed solution was further subjected to diafiltration using a spiral-wound membrane, ultimately yielding fructose and HEPES solutions with purities of 90.22 % and 92.93 %, respectively. Combining separation test results with models such as DSPM-DE, and using characterization methods such as ATR-FTIR and pore size distribution analysis, we observed pore swelling during nanofiltration of the HEPES-fructose solution at pH 9.0. A mechanism for this pore swelling, induced by the dissociation of HEPES under the influence of pH, was proposed: Dissociated HEPES in the solution interacts with the membrane surface at the liquid-membrane interface, causing reversible swelling of the membrane pores at the membrane surface, thereby reducing the retention rate of fructose. The nanofiltration process developed in this study effectively separates HEPES and fructose, enabling resource recycling and cost reduction. Furthermore, this study provides theoretical foundations and practical guidance for the design of nanofiltration separation strategies for similar systems using HEPES as a buffer, holding significant scientific and practical value.

Establishment of circular economy by utilising textile industry waste as an adsorbent for textile dye removal

This study explored the use of waste from the textile industry (silkworm byproducts) as a promising raw feedstock for the production of carbon-based adsorbents (biochar). The silk excreta biochar generated at 600 and 700 °C (referred to as SEB-600 and SEB-700, respectively) were evaluated in terms of their efficacy in adsorbing cationic (methylene blue) and anionic (Congo red) textile dyes. Although the functional groups on the surfaces of SEB-600 and SEB-700 were not significantly different, the specific surface area of SEB-700 was greater than that of SEB-600. The dye adsorption capacity of SEB-700 was higher than that of SEB-600. The adsorption of methylene blue and Congo red on SEB-700 followed Freundlich isotherms (R2 ≥ 0.963) and pseudo-second-order kinetics (R2 = 0.999), indicating chemisorption with multilayer characteristics. The mechanism for the adsorption of methylene blue on SEB-700 may involve interactions with the negatively charged functional groups on the surface and the mesopores of SEB-700. For the adsorption of Congo red, the mesopores in the biochar and the electrostatic interaction between biochar (positively charged because of the dye solution pH < pHzpc) and the anionic dye could affect adsorption. The maximum adsorption capacities of SEB-700 for methylene blue and Congo red were determined to be 168.23 and 185.32 mg g−1, respectively. Utilising the waste generated from the textile industry to remove pollutants will build a sustainable loop in the industry by minimising waste generation and pollutant emissions.

Alteration of the upper critical solution temperature (UCST) behavior of the nonionic polymer poly(N-acryloyl-nipecotamide) by its terminal group

Influences of the terminal group of non-ionic polymer with upper critical solution temperature on cloud points (CPs) has been one of curious research topics, however, detailed investigation has not been conducted so far. This study investigates the effect of the terminal group of poly(N-acryloyl-nipecotamide)s (PNANAms) on their CPs in aqueous solution. PNANAms with different molecular weights (Mn) ranging from 4,100 to 34,300 and different terminal end groups were successfully synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. The temperature-dependent optical transmittance of aqueous solutions of the PNANAms revealed that their CP was influenced by their terminal group, in addition to their Mn and polymer concentration. PNANAms with low Mn (Mn ≥ 7,500) and a hydrophobic (dodecyl) terminal group exhibited poor solubility, whereas PNANAms with a moderate Mn (Mn ≤ 10,200) and hydrophilic (maleimide or carboxylic) terminal groups were readily soluble in aqueous solution. However, PNANAms with a high Mn (Mn = 34,300) were hardly soluble in aqueous solution. The poor solubility of such PNANAms suggests that strong inter- and intramolecular hydrogen bonds were formed among the polymer chains, increasing their CP. PNANAm with a low Mn (Mn = 4,100) and the hydrophobic terminal and that with a moderate Mn (13,200 ≤ Mn ≤ 18,200) and hydrophilic terminal groups exhibited CPs in aqueous solution. The CP of PNANAms with carboxylic terminal groups was also influenced by the solution pH owing to the deprotonation of these groups. The size of polymeric aggregates was directly observed using phase-contrast microscopy, and the temperature-dependent aggregation and dispersion of the polymers were described in terms of the inter- and intramolecular hydrogen bonds formed among PNANAm chains. Finally, a cell viability assay was conducted to explore the possibility of the applications of PNANAm in the fields of biomaterials and regenerative therapy.

A Novel Process for the Separation of Rare Earth Elements to Recover Pure Nd(III) Solution from the NdFeB Magnets

ABSTRACT FeNdB magnets are one of the important secondary resources containing rare earth elements (REEs). The REEs present in FeNdB magnets can be separated from other metals by double salt precipitation. In order to recover pure Nd(III) solution from the double salts, separation experiments were done with the leaching solutions of the double salts containing Ce(III), Nd(III), and Pr(III). The REEs present in the double salts were completely dissolved using 0.5 M HCl solution at room temperature. First, Ce(III) was separated by oxidative precipitation of CeO2 and Ce(OH)4 by using NaClO and NaOH as an oxidizing and neutralizing agent. Complete separation of Ce(III) from the leaching solution of the double salts was possible by controlling solution pH at 5 under the following conditions: 11 for the molar ratio of NaClO/Ce(III) and 400 rpm at 40°C for 60 min. Second, all the Nd(III) and Pr(III) ions present in the filtrate were completely extracted by using saponified D2EHPA. Third, four stages of cross-current scrubbing of the loaded D2EHPA with pure Nd(III) solution removed most of the Pr(III) from the loaded D2EHPA. Finally, pure Nd(III) solution was obtained by stripping the scrubbed D2EHPA with weak HCl solution. The optimum conditions for the extraction, scrubbing, and stripping were obtained. A simple process was proposed to recover Nd(III) solution with purity higher than 99.9% from FeNdB magnets.

Analysis of the Structure of 14 Therapeutic Antibodies Using Circular Dichroism Spectroscopy.

Understanding the impact of the manufacturing environment on therapeutic monoclonal antibody (mAb) structures requires new process analytical technology. Here, we describe the creation of a new reference set for the circular dichroism (CD) spectra of mAbs. Data sets of the highest quality were collected by synchrotron radiation CD for 14 different mAbs in both native and acid-stressed states. Deconvolution of far-UV spectra for the mAb cohort identified two current reference sets (SP175 and SMP180) as assigning accurate secondary structures, irrespective of the analysis program employed. Scrutiny of spectra revealed significant variation in the far-UV and especially near-UV CD of the 14 mAbs. Two spectral features were found to be sensitive to changes in solution pH, i.e., the far-UV positive peak at 201-202 nm and the near-UV negative exciton couplet around 230-240 nm. The latter feature offers attractive possibilities for in-line CD-based monitoring of the mAb structure during manufacture.