Tested pH Range Research Articles

Experimental investigation of sodium ion adsorption on polyacrylic acid grafted graphene oxide polymeric adsorbent: Kinetics, isotherms, and performance analyses

In this study, the sodium ion adsorption, as a desalination process of saline water, on polyacrylic acid grafted on graphene oxide (PAA-g-GO) was investigated. According to the results of GPC and FTIR analyses, it was confirmed that the synthesized adsorbent has a very effective function for Na+ adsorption. The remarkable finding about the synthesized adsorbent was that in all the tested pH range (8–10) and sodium ion concentrations (0.1–1 M), the measured adsorption capacities were reported to be more than 1750 mg/g. However, it is interesting that the maximum adsorption capacity was obtained a significant amount of 7462.31 mg/g at pH =10. According to the adsorption kinetics analysis results, the equilibrium time was obtained about 90 min. Also, by examining the effect of pH on the amount of sodium ion adsorption, it was found that it increased by increasing pH value. Adsorption data were also modeled with the Redlich-Peterson isotherm with R2 greater than 0.99 for all range of examined pHs. By examining the effect of adsorbent dosage on Na+ adsorption, it was found that the effect of the adsorbent dosage was very high at low initial concentrations (0.1 to 0.2 M), but this effect decreased by increasing the dosage.

Always positive covalent organic nanosheet enabling pH-independent adsorption and removal of Cr(Ⅵ)

Rapid and highly effective removal of hexavalent chromium (Cr(Ⅵ)) is extremely vital to water resources restoration and environmental protection. To overcome the pH limitation faced by most ionic absorbents, an always positive covalent organic nanosheet (CON) material was prepared and its Cr(VI) adsorption and removal capability was investigated in detail. As-prepared EB-TFB CON (TFB = 1,3,5-benzaldehyde, EB = ethidium bromide) shows strong electropositivity in the tested pH range of 1 ∼ 10, display a pH-independent Cr(VI) removal ability, and work well for Cr(VI) pollution treatment with good anti-interference capability and reusability in a wide pH range covering almost all Cr(VI)-contaminated real water samples, thus eliminating the requirement for pH adjustment. Moreover, the nanosheet structure, which is obtained by a facile ultrasonic-assisted self-exfoliation, endows EB-TFB CON with fully exposed active sites and shortened mass transfer channels, and the Cr(VI) adsorption equilibrium can be reached within 15 min with a high adsorption capacity of 280.57 mg·g−1. The proposed Cr(VI) removal mechanism, which is attributed to the synergetic contributions of electrostatic adsorption, ion exchange and chemical reduction, is demonstrated by experiments and theoretical calculations. This work not only provides a general Cr(VI) absorbent without pH limitation, but also presents a paradigm to prepare ionic CONs with relatively constant surface charges.

One-pot synthesis of quaternized microcrystalline cellulose obtained from soybean hulls

A novel quaternized microcrystalline cellulose (Q-MCC) was obtained through a one-pot synthesis using agro-industrial waste, specifically soybean hulls (SBH), as the starting material. This work focuses on discussing the synthesis, physicochemical characterization, and application of Q-MCC, particularly its potential use in the removal of industrial textile dyes. The material underwent various characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), optical microscopy, thermogravimetric analysis/differential thermal analysis (TGA/DTA), and differential scanning calorimetry (DSC). Additionally, Kjeldahl analysis, swelling measurements, and determination of the pH at the zero-point charge (pHzpc) were performed. FTIR spectroscopy confirmed the presence of attached quaternary ammonium groups. SEM and XRD analysis of Q-MCC revealed that the material consisted of short fibers with an average length of 30.93 µm and exhibited an increased crystallinity index of 76.4 %, respectively. Moreover, the pH at the point of zero charge (pHpzc) indicated that the adsorbent displayed a cationic nature across the tested pH range. The modification of SBH led to enhanced water absorption, and excellent dye removal results were achieved using two types of dyes: Direct Black 22 (DB 22) and Reactive Orange 122 (RO 122). To further investigate the behavior of Q-MCC in the adsorption of DB 22 dye, various studies were conducted, including kinetic, adsorption, thermodynamic analyses, and Weber-Morris intraparticle diffusion analysis. The kinetics results demonstrated that more than 90 % of the dye was adsorbed within just one minute of contact and were better represented by the pseudo-second order model, while the maximum adsorption capacity was approximately 470 mg/g. The experimental data fit very well with the Langmuir isotherm model. The adsorption process was determined to be exothermic, and the mechanism was proposed to be electrostatic interaction between the quaternary ammonium moiety and negatively charge anionic dyes. Finally, the Weber-Morris study suggested that both film diffusion and intraparticle diffusion contribute to the adsorption process.

Fluorescence intensity and fluorescence lifetime measurements of various carbon dots as a function of pH

Measurement and monitoring of pH are essential in both the industry and academia. It is therefore important to continue developing novel, low-cost pH sensors that provide increased accuracy over long periods of time. Particularly promising are sensors based on materials that show pH-dependent fluorescence intensity (FI) and lifetime (FL). Carbon dots (CDs) are emerging as promising candidates because of their low cost, ease of manufacturing, low toxicity, and negligible photobleaching. However, little has been done to quantify the FI and FL values of CDs. Here we report the characterisation of the pH-dependent FI and FL of four novel solvothermal synthesised CDs. The fifth CD is used as a reference sample and was synthesised following a published synthesis. The precursors for the CDs include disperse blue 1 dye, phloroglucinol, m-phenylenediamine (m-PD), N, and N-dimethylformamide (DMF). The average diameter size of the CDs ranges from 1.5 to 15 nm. An excitation wavelength of 452 nm with a bandwidth of 45 nm was used to quantify the fluorescence in the pH range 5–9. Three CDs show a decreasing trend in FI with pH, while two CDs show an increasing trend. None of the CDs shows strong FL dependence. The FL changes around 0.5 ± 0.2 ns across the tested pH range. We suggest that the differences in the fluorescence trends can be attributed to the precursors chosen for synthesising the CDs.

A novel route for the facile synthesis of NH2-MIL-53(Fe) and its highly efficient and selective adsorption of congo red

Metal-organic frameworks (MOFs) have shown attractive advantages in adsorbing dyes from wastewater. However, their complex synthesis processes and poor stability have limited their applications. Herein, we proposed a novel two-step route to prepare NH2-MIL-53(Fe) at room temperature and investigated its dye adsorption performance. The prepared NH2-MIL-53(Fe) displayed high water stability in the pH range of 3–11. Moreover, NH2-MIL-53(Fe) showed a significantly higher adsorption capacity and faster adsorption rate towards congo red (CR) than the other selected dyes, with more than 99 % of CR being removed by NH2-MIL-53(Fe) within 20 min. The maximum adsorption capacity of NH2-MIL-53(Fe) for CR was 1877 mg·g−1. Besides, the removal efficiency of CR could maintain higher than 80 % within the tested pH range (3 to 11), and removal efficiency was consistently higher than 95 % at different NaCl concentrations (0 to 0.4 M). The dynamic CR adsorption process matched the pseudo-second-order kinetic model and fitted well using the Langmuir model, suggesting that the adsorption of CR onto NH2-MIL-53(Fe) was a monomolecular-layer chemical adsorption process. More importantly, NH2-MIL-53(Fe) showed high removal efficiency and good reusability towards CR in both synthetic and model wastewater. Mechanistic studies suggested that the removal of CR was attributed to the synergistic effects of the π-π stacking interactions, hydrogen bonds and electrostatic interactions between CR and NH2-MIL-53(Fe). Overall, the present study provides a novel strategy for the facile synthesis of NH2-MIL-53(Fe), highlights the excellent adsorption performance and reusability towards CR and underlies the adsorption mechanisms involved.

Competition between electrostatic interactions and halogen bonding in the protein–ligand system: structural and thermodynamic studies of 5,6-dibromobenzotriazole-hCK2α complexes

CK2 is a member of the CMGC group of eukaryotic protein kinases and a cancer drug target. It can be efficiently inhibited by halogenated benzotriazoles and benzimidazoles. Depending on the scaffold, substitution pattern, and pH, these compounds are either neutral or anionic. Their binding poses are dictated by a hydrophobic effect (desolvation) and a tug of war between a salt bridge/hydrogen bond (to K68) and halogen bonding (to E114 and V116 backbone oxygens). Here, we test the idea that binding poses might be controllable by pH for ligands with near-neutral pKa, using the conditionally anionic 5,6-DBBt and constitutively anionic TBBt as our models. We characterize the binding by low-volume Differential Scanning Fluorimetry (nanoDSF), Isothermal Calorimetry (ITC), Hydrogen/Deuterium eXchange (HDX), and X-ray crystallography (MX). The data indicate that the ligand pose away from the hinge dominates for the entire tested pH range (5.5–8.5). The insensitivity of the binding mode to pH is attributed to the perturbation of ligand pKa upon binding that keeps it anionic in the ligand binding pocket at all tested pH values. However, a minor population of the ligand, detectable only by HDX, shifts towards the hinge in acidic conditions. Our findings demonstrate that electrostatic (ionic) interactions predominate over halogen bonding.

Enhanced desorption of cationic and anionic metals/metalloids from co-contaminated soil by tetrapolyphosphate washing and followed by ferrous sulfide treatment

In this study, a novel approach was employed for the remediation of cationic and anionic metals/metalloids co-contaminated soil by tetrapolyphosphate enhanced soil washing coupled with ferrous sulfide treatment. Tetrapolyphosphate could simultaneously enhance the desorption of cationic metals (Pb and Zn) and anionic metal/metalloid (Cr and As) from the contaminated soil in the whole tested pH range of 2–10. With addition of 0.15 mol/L tetrapolyphosphate at pH 7.0, the removal ratio of Pb, Zn, As and Cr could achieve 83.1%, 70.4%, 75.7% and 66.4% respectively. The fractionation analysis of heavy metals/metalloids demonstrated the release of exchangeable and Fe/Mn bound forms contributed to most desorption of Pb and Zn. The decreases of non-specifically sorbed form and amorphous and poorly-crystalline hydrous oxides of Fe and Al bound form were responsible for most removal of As. The comparison with other common washing agents (EDTA, oxalate and phosphate) under their respective optimal dosage could confirm that tetrapolyphosphate was superior to simultaneously desorb the cationic and anionic metals/metalloids with higher efficiency. After 12 h, applying 150 mg/L FeS at pH 3.5 could totally remove Pb, Zn, As and Cr from the washing effluent by sulfide precipitation, reduction and adsorption processes. Higher pH would inhibit the removal of As and Cr by FeS. Meanwhile, the residual of tetrapolyphosphate could be totally recovered from the washing effluent by employing anion exchange resin. This study suggests tetrapolyphosphate enhanced soil washing coupled with ferrous sulfide treatment is a promising approach for remediation of cationic and anionic metals/metalloids co-contaminated soil in view of its high efficiency and simple operation.

Aluminum sampling by Chelex, titanium dioxide and zirconium oxide DGT: Influence of pH on accumulation behaviors

Diffusive gradient in thin film (DGT) is used for aluminum monitoring in waters, where content can reach more than 1 mg L −1 , but no information is available concerning its limit of linear accumulation, leading to a risk of an underestimation of the water concentration. Furthermore, this limit can be strongly affected by the pH due to changes of the aluminum speciation and global charge of the binding phase. The linear accumulation capacities of three types of DGT, based on Chelex-100® (DGT-Ch), titanium dioxide (DGT-Ti) and zirconium oxide (DGT-Zr), were determined as a function of pH by time-series accumulation over 30 days. For DGT-Ch, it decreased with increasing pH: around 16 μ g at pH 4.1, 5 μ g at pH 5.3 and null at pH 8.6. The DGT-Ti and DGT-Zr had similar performances and could accumulate aluminum over the whole tested pH range, but with a significantly higher limit of linear accumulation at pH 8.6 ( ≈ 15 μ g) compared to pH 4.1 ( ≈ 1 μ g). The evolution of the accumulated mass over time agreed with the predicted values except for DGT-Zr at pH 4.1 and 5.3, where a ca 30% higher accumulation was observed. Application in natural freshwaters containing various aluminum species and potential competitors confirmed the linear limits for the three types of DGT and also the DGT-Zr tendency to over-estimate aluminum (up to 200% in some freshwater samples compared to DGT-Ch and DGT-Ti). This phenomenon observed for DGT-Zr cannot be explained yet. Currently, DGT-Zr is not recommended for aluminum monitoring. • Linear accumulation capacities of three binding phases were determined according to pH. • Up to ten-fold variations between pH 4.1 and 8.6 for DGT-Ti and DGT-Zr. • Similar capacities and accumulation behaviors in NaNO 3 and in natural waters. • DGT-Zr was tested for the first time and seems to overestimate Al concentration.

The Influence of pH on Zinc Lability and Toxicity to a Tropical Freshwater Microalga.

Increased focus on the development and application of bioavailability-based metal water quality guideline values requires increased understanding of the influence of water chemistry on metal bioavailability and toxicity. Development of empirical models, such as multiple linear regression models, requires the assessment of the influence of individual water quality parameters as toxicity-modifying factors. The present study investigated the effect of pH on the lability and toxicity of zinc (Zn) to a tropical green microalga (Chlorella sp.). Zinc speciation and lability were explored using the Windermere Humic Aqueous Model (WHAM7), ultrafiltration, and diffusive gradients in thin films (DGT). Zinc toxicity increased significantly with increasing pH from 6.7 to 8.3, with 50% growth inhibition effect concentrations decreasing from 185 to 53 µg l-1 across the pH range. Linear relationships between DGT-labile Zn and dissolved Zn did not vary across the tested pH range, nor did the linear relationship between dissolved (<0.45 µm) and ultrafiltered (<3 kDa) Zn. Our findings show that Zn toxicity to this freshwater alga is altered as a function of pH across environmentally realistic pH ranges and that these toxicity changes could not be explained by Zn speciation and lability as measured by DGT and WHAM7. Environ Toxicol Chem 2021;40:2836-2845. © 2021 SETAC.

Insights into the Conformation and Self-Association of a Concentrated Monoclonal Antibody using Isothermal Chemical Denaturation and Nuclear Magnetic Resonance

The purpose of this investigation was to highlight the utility of nuclear magnetic resonance (NMR) as a multi-attribute method for the characterization of therapeutic antibodies. In this case study, we compared results from isothermal chemical denaturation (ICD) and NMR with standard methods to relate conformational states of a model monoclonal antibody (mAb1) with protein-protein interactions (PPI) that lead to self – association in concentrated solutions. The increase in aggregation rate and relative viscosity for mAb1 was found to be both concentration and pH dependent. The free energy of unfolding (∆G⁰) from ICD and thermal analysis in dilute solutions indicated that although the native state predominated between pH 4 – pH 7, it was disrupted at the CH2 and unfolded noncooperatively under acidic conditions. One-dimensional (1D) 1H NMR and two-dimensional (2D) 13C-1H NMR performed, in concentrated solutions, confirmed that PPI between pH 4–7 occurred while mAb1 was in the native state. NMR corroborated that mAb1 maintained a dominant native state at formulation-relevant conditions at the tested pH range, had increased global molecular tumbling dynamics at lower pH and confirmed increased PPI at higher pH conditions. This report aligns and compares typical characterization of an IgG1 with assessment of structure by NMR and provided a more precise assessment and deeper insight into the conformation of an IgG1 in concentrated solutions.

Pycnogenol - extract from French maritime pine bark (Pinus pinaster), as an effective antioxidant against superoxide radical

Background: Interest in the positive impact of naturally occurring polyphenols is still increasing in the scientific community. Research is focused mainly on their antioxidant properties, due to their significant effects in the prevention of diseases associated with oxidative stress. Pycnogenol is an extract from French maritime pine bark (Pinus pinaster), which is composed of a mixture of phenolic compounds: monomers (catechin, epicatechin, taxifolin), flavonoids (classed as procyanidins/proanthocyanidins), phenolic or cinnamic acids and their glycosides. Due to its composition, it has a high antioxidant capacity, and is used in traditional folk medicine, cosmetics and medicine.Purpose of the study: The aim is to study the antioxidant properties of pycnogenol in order to obtain experimental information on the antioxidant effect of pycnogenol in terms of concentration dependence and pH conditions.Methods: In our study, we used a methionine-riboflavin superoxide generator, and focused on determining the antioxidant capacity of Pycnogenol against the superoxide radical in different pH values (range 6.5 – 8) using the spectroscopic method.Results: Our results showed that the antioxidant properties increased with a higher concentration of the tested compound in the tested pH range. Amongst all tested pH values, the most appropriate for pycnogenol antioxidant capacity is slightly basic pH (pH 8).Conclusion: Information on the antioxidant and prooxidant properties of naturally occurring compounds is very important for understanding their activity and their proper use in prevention, disease treatment, and detection of pathological processes. The antioxidant activity of pycnogenol depends on the structure and concentration of antioxidants; it only slightly changes at different pH values. Increasing concentration of pycnogenol enhances its antioxidant properties.Keywords: Pycnogenol, reactive oxygen species, spectrophotometry, pH dependency

Physicochemical and Antioxidative Characteristics of Potato Protein Isolate Hydrolysate.

This study investigated the physicochemical characteristics of potato protein isolate hydrolysate (PPIH) and its antioxidant activity. Potato protein isolate (PPI) was hydrolyzed into PPIH by the proteases bromelain, Neutrase, and Flavourzyme. Compared with PPI, the resulting PPIH had a lower molecular weight (MW, from 103.5 to 422.7 Da) and smaller particle size (<50 nm), as well as a higher solubility rate (>70%) under acidic conditions (pH 3–6). PPIH presented good solubility (73%) across the tested pH range of 3–6. As the pH was increased, the zeta potential of PPIH decreased from −7.4 to −21.6. Using the 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical-scavenging assay, we determined that the half-maximal effective concentration (EC50) values of ascorbic acid, PPIH, and PPI were 0.01, 0.89, and >2.33 mg/mL, respectively. Furthermore, PPIH (50 μg/mL) protected C2C12 cells from H2O2 oxidation significantly better than PPI (10.5% higher viability rate; p < 0.01). These findings demonstrated the possible use of PPIH as an antioxidant in medical applications.

The influence on biosorption potentials of metal-resistant bacteria Enterobacter sp. EG16 and Bacillus subtilis DBM by typical red soil minerals

Due to the inevitable interaction between bacteria and soil minerals, whether bacteria could exert the excepted functions in the soil is yet to be confirmed and how minerals affect biosorption potential is needed to be investigated. The purposes of this study were to explore the adsorption behavior and mechanism of metal-resistant bacteria attaching to typical red soil minerals under different conditions and to discuss whether biosorption potential would be altered after the addition of functional bacteria to soil. Here, we tested equilibrium adsorption along with zeta potential analysis, scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and desorption to investigate the adsorption of two metal-resistant bacteria (Gram-negative Enterobacter sp. EG16 and Gram-positive Bacillus subtilis DBM) onto typical red soil minerals including goethite, kaolinite, and gibbsite under different environmental factors. We found that the minerals adsorbed more EG16 cells than DBM, and the adsorption capacities followed the sequence of goethite > kaolinite > gibbsite. Both the surfaces of bacteria and mineral were pH-dependent in our tested pH range (4.0–7.0), and the maximum adsorption was at pH 4.0. Increasing ionic strength resulted in less adsorption of bacteria onto goethite, whereas bacterial adsorption onto kaolinite was the opposite. These observations elucidated that electrostatic interaction was the dominant contributor. The adsorption conformed to the Langmuir and pseudo-second-order kinetic model implying chemical adsorption, and the result of FTIR also supported that. Desorption experiment has suggested the significant contribution of electrostatic force and the minor dominator of functional groups for bacteria–mineral combination. The results of this study indicated that electrostatic interaction was the dominant contributor to bacteria–mineral combination and functional groups coordination contributed less than 10%. This finding suggested most adhered bacteria could still provide active sites for heavy metal biosorption. Thus, although 50–90% of added functional bacteria has adhered to minerals, the bacteria–mineral combination had a limited impact on biosorption.

Enhanced removal of chromium(III) for aqueous solution by EDTA modified attapulgite: Adsorption performance and mechanism

Ethylenediaminetetraacetic acid modified attapulgite (EDTA-ATP) was developed as a novel and promising adsorbent for removal of aqueous Cr(Ш). The structure and surface properties of EDTA-ATP were characterized and the results indicated that EDTA moieties have been successfully anchored on the surface of ATP. Adsorption of Cr(III) on EDTA-ATP and aminopropyl-modified attapulgite (APTES-ATP) monotonously reduced with decreasing pH, and Cr(III) adsorption on EDTA-ATP is substantially higher than APTES-ATP in tested pH range, especially at lower pH. Presence of citric acid and gelatin had no obvious influence on Cr(III) adsorption to EDTA-ATP, but significantly reduced Cr(III) adsorption on APTES-ATP. Coexisting cations resulted in decreased Cr(III) adsorption on EDTA-ATP by competition with Cr(III) for surface-bound EDTA groups of the adsorbent. Adsorption isotherm of Cr(III) on EDTA-ATP followed the Langmuir model and the maximum adsorption capacity of the adsorbent for Cr(III) was 131.37 mg/g at 25 °C and pH 3.0. Cr(Ш) loaded adsorbent could be regenerated easily in HCl solution and the regenerated adsorbent still exhibited high adsorption capacity for Cr(III). XPS analysis confirmed that the enhanced Cr(III) adsorption on EDTA-ATP was ascribed to form the stable complexes between Cr(III) and surface-bound carboxyl and amino groups of the adsorbents.

Homogeneous catalytic activation of peroxymonosulfate and heterogeneous reductive regeneration of Co2+ by MoS2: The pivotal role of pH

The application of MoS2 to enhance Co(II)/peroxymonosulfate (Co(II)/PMS) system for organic pollutants degradation was developed, and the mechanism for pH dependent catalytic activity in the MoS2 co-catalyzed Co(II)/PMS processes was systematically investigated. It was found that MoS2 presented enhancement effect for Co(II)/PMS system in the tested pH range from 4.0 to 7.0, especially at pH 5.5 and 6.0. The pseudo first order reaction rates for Rhodamine B (RhB) degradation in MoS2-Co2+/PMS system at pH 5.5 and 6.0 were 3.2 and 1.8 times that in Co2+/PMS system (Co2+ 2 μmol L−1, PMS 0.2 mmol L−1, MoS2 0.5 g L−1). The redox recycle of Co3+/Co2+ was promoted by Mo(IV) and S(-II) on MoS2 surface and regenerated Co2+ induced homogeneous activation of PMS for the robust production of free radical with the major of hydroxyl radicals. Increasing MoS2 dosage, Co2+ and PMS concentration can linearly raise RhB degradation rate in MoS2-Co(II)/PMS system. Moreover, MoS2 exhibited excellent catalytic and chemical stability in recyclability and reuse for catalytic decontamination in MoS2-Co(II)/PMS system. This work gains new insight into the enhancement effect of MoS2 in the meal ions/PMS system, and provides a high performance wastewater treatment process of Co(II)/PMS at low concentrated Co2+.

Novel edible pickering high-internal-phase-emulsion gels efficiently stabilized by unique polysaccharide-protein hybrid nanoparticles from Okara

The development of high-performance and biocompatible Pickering stabilizers for O/W high internal phase emulsions (HIPEs) has attracted fast increasing interests in the food colloid areas, due to their potential applications in food and pharmaceutical formations. This work reports that a kind of nanoparticles (ISPN; with a size of about 160 nm), facilely fabricated by a high power ultrasonication treatment from the insoluble soy polysaccahrides of Okara (a byproduct of soybean processing), could perform as an outstanding Pickering stabilizer for HIPEs. The structure of the nanoparticles, mainly composed of polysaccharides and proteins, was stable over the test pH or ionic strength range (pH 2.0–12.0 or 0–500 mM). The formation, microstructure and rheology of the HIPE gels stabilized by the ISPN were investigated in terms of visual and microscopic observations, laser diffraction technique, and dynamic oscillatory measurements. The results indicated that the HIPE gels with soy oil as the dispersed phase could be formed at a particle concentration (c) as low as 0.25 wt%, and increasing the c (from 0.25 to 1.5 wt%) led to a progressive strengthening of their gel network, as well as a progressive decrease in their droplet size. The HIPE gels could be formed over the whole test pH (2.0–12.0) or ionic strength (0–500 mM) range, and their gel network could not be dispersed by 6.0 M urea or 1.0 wt% SDS. In addition, the fabricated HIPE gels exhibited an excellent stability upon a prolonged storage and heating at temperatures ranging from 50 to 90 °C, as well as an unique temperature responsiveness. All the observations demonstrated that the ISPN exhibited a great potential to perform as Pickering stabilizers for HIPEs, with the emulsification performance and ability to form the HIPE gels much better than those reported previously. The findings would be of interest not only for the development of a kind of novel edible HIPEs suitable for health food formulations, but also for guiding the high-added-value ultilization of the byproduct (Okara) of soybean processing industries.

Direct UV photolysis of pharmaceutical compounds: Determination of pH-dependent quantum yield and full-scale performance

When using municipal wastewater as a potable water source, advanced treatment is mandatory for the removal of trace organic contaminants, including pharmaceuticals. UV-radiation (254 nm) is frequently used in combination with hydrogen peroxide at the end of the advanced treatment train for simultaneous disinfection and degradation of trace organic contaminants. In this work, a comprehensive study on the direct UV photolysis of eleven organic compounds (including ten pharmaceuticals and N-Nitrosodimethylamine (NDMA)) was conducted at varying pH of 5–8 using a collimated beam apparatus. Molar extinction coefficient (ε) and quantum yield (QY) values of different ionic forms (cationic, neutral and anionic) for eleven organic compounds were estimated in the tested pH range. Furthermore, direct UV photolysis at a full-scale UV photoreactor with 30 low-pressure UV lamps was performed at pH 6.2 and 7.8 by varying water flow rates (375–2700 L min−1) and UV fluences (400–4000 mJ cm−2). A process model was developed to determine the log reduction of the test compounds. The model combines a Lagrangian fluence model in the photoreactor with a pH-dependent photochemical kinetic model that ulilized the measured molar extinction coefficient and quantum yield values. The observed log reductions matched well with the model predictions for most of the tested compounds.

Sulfonation of Phenolated Kraft Lignin to Produce Water Soluble Products

Kraft lignin is water insoluble and has limited end-use applications. To produce water soluble lignin-based products, the modification of softwood kraft lignin through phenolation followed by sulfonation of sulfuric acid or sodium sulfite treatment were investigated in this work. Fourier transform infrared (FTIR) spectrophotometer, nuclear magnetic resonance (NMR), and thermo-gravimetric analysis were also considered for characterizing the lignin-based products. The results showed that phenolation pretreatment was effective to generate sulfonated lignin (SAP-lignin) by sulfuric acid treatment with a high charge density (3.12 meq/g) and solubility, which is due to the addition of sulfonation sites on the phenolic ring. However, sodium sulfite treatment of phenolated lignin generated sulfonated lignin (SSP-lignin) with the charge density of 1.20 meq/g due to hindered sulfonation by occupation of reactive α-position. SAP-lignin was soluble across the tested pH range of 1–13, but SSP became insoluble at a pH lower than 3. Thermogravimetric analysis revealed that phenolation pretreatment reduced the thermal resistance of modified lignin when compared to kraft lignin, while SAP-lignin exhibited the highest thermal resistance due to condensation under sulfuric acid treatment. SAP- and SSP-lignin were successfully used as a coagulant for dye removal from simulated solutions as they could remove 72.1 and 90.4% of ethyl violet from a simulated dye solution, respectively.

Effect of Bath pH on Electronic and Morphological Properties of Electrodeposited Cu2O Thin Films

The ability to systematically vary the flatband potential and the band edge positions of Cu2O by varying the deposition bath pH is considered important in the context of using Cu2O for photocatalytic water splitting. Capacitance-voltage (C-V) and dark and light current-voltage measurements were taken in order to investigate the electronic properties of electrodeposited Cu2O thin films grown in an acetate bath containing a 0.01 M Cupric Acetate having different bath pH values. The Mott-Schottky plots resulting from C-V measurements revealed that the flatband potential and doping density of the films strongly depended on the deposition bath pH. For pH values lower than 7.2, conductivity of Cu2O films remained n-type while it changed to p-type for higher pH values indicating that change of n-type to p-type character of the Cu2O films can be controlled by the bath pH. With increasing pH value, the grain size decreased, while crystal shapes transformed from truncated octahedral to cubic within the tested pH range. A well ordered cubic structure was observed in films deposited at pH 7.8. The rate of deposition decreased at higher pH values leading to thinner films indicating the effect of pH on the film thickness. Calculated band edge positions of conduction and valance bands of the Cu2O films were −4.19 eV and −6.29 eV respectively with respect to the vacuum level.

Removal of bacteriophage f2 in water by Fe/Ni nanoparticles: Optimization of Fe/Ni ratio and influencing factors

Pathogenic viruses in water are seriously harmful to human health and highly resistant to conventional disinfections. As a kind of promising attempts for pollution remediation, Fe-based nanoparticles show excellent performance in removing contaminants. In this study, the Fe/Ni nanoparticles (Fe/Ni NPs) were synthesized using the self-designed device and used for bacteriophage inactivation in water. Scanning electron microscope (SEM) and X-ray diffraction (XRD) showed that the as-prepared Fe/Ni particles were spherical and the average particle size was 93 nm. The synthesized Fe/Ni NPs achieved much higher removal efficiency of bacteriophage f2 than nanoscale zero-valent iron (nZVI), while Ni nanoparticles (Ni NPs) showed no removal effect on the bacteriophage f2. The highest removal efficiency of bacteriophage f2 by Fe/Ni NPs was obtained when the primary ratio of Fe:Ni was 5:1. In addition, the removal efficiency of phage f2 under aerobic condition was significantly higher than that under anaerobic condition with Fe/Ni NPs, and the role of Ni was proved as a catalyst in the system. Besides, the effect of initial pH, initial concentration of bacteriophage f2, particles dose, rotation rate, and temperature on the removal efficiency of bacteriophage f2 were studied. The result showed that the removal efficiency of bacteriophage f2 did not change obviously in the test pH range (5–8), and was positively related with the rotation rate and negatively related with the initial concentration of bacteriophage f2. The particles dose could increase the removal efficiency of phage f2, but the removal efficiency would decrease when the dose was too much due to the aggregation of nanoparticles. The increase of temperature could increase the removal efficiency initially, but decrease the removal efficiency finally due to the accelerated corrosion of iron.