Aqueous Phosphate Research Articles

Sanky (Corryocactus brevistylus) Peel as Low-Cost Adsorbent for Removal of Phosphate from Aqueous Solutions

This study aimed to evaluate the adsorption capacity of an adsorbent obtained using sanky peel for the removal of phosphate from aqueous solutions. The study was conducted in two stages: (1) adsorbent preparation considering yield, phosphate removal, adsorption capacity, and textural characteristics; (2) an assessment of the effectiveness of using sanky peel as an adsorbent for removing phosphates from aqueous solutions. Batch adsorption was studied in aqueous solutions containing phosphate and calcium ions with the selected adsorbent. Adsorption kinetics and equilibrium isotherms were studied using mathematical models. The adsorption kinetics followed the pseudo-second-order, Elovich, and Weber–Morris models, thus demonstrating that adsorption rates were not controlled by multiple processes. Adsorption equilibrium data fitted best with the Dubinin–Radushkevich model. Finally, a Fourier transform infrared spectroscopy analysis revealed the presence of brushite spectra bands after adsorption. The results of this study can help better understand the use of sanky peel as an adsorbent and good alternative for aqueous phosphate adsorption.

Pyrolyzed Ca-impregnated lignite for aqueous phosphate removal: Batch and column studies

Lignite is an abundant carbon material with a variable surface structure and low cation density The introduction of metal (hydr)oxide phases has improved the anionic binding potential of lignite. In this study, activated lignite (A−L), Ca2+−modified lignite (Ca−L), and Ca2+−modified activated lignite (Ca−A−L) were synthesized to remove aqueous phosphate. Lignite was first activated (KOH: lignite, mass ratio, 3:1) at 750 ºC to prepare A−L, improving its surface area by ~984-fold. Ca−L (27 wt% Ca) showed a large phosphate uptake (227.3 mg/g) (adsorbent dose 50 mg, 25 mL of 10–1500 ppm phosphate, 24 h, 25 °C, initial pH 6), due to the large amounts of micro-sized CaCO3, Ca(OH)2, and CaO particles in Ca−L. These particles actively precipitate phosphate/hydrophosphate as CaHPO4/Ca3(PO4)2. The breakthrough capacity of a 2.0 g Ca−L bed column (bed height 2.5 cm, diameter 1 cm) was 58.2 mg/g (flow rate 1.5 mL/min, 25 ºC, initial [PO43-] = 46.6 mg/L, particle size, 125–150 µm), ~4 fold lower than the maximum Langmuir sorption capacity. An interference study indicated that Ca−L is highly selective for phosphate. Spent Ca−L may improve soil fertility as it retains more phosphate species for later slow-release to the soil. Unit weight of phosphate can be removed by Ca−L more inexpensively than Norit ROW and Darco KB (two commercial activated carbon carbons). Precipitated Ca2+ phosphates/hydrophosphates in exhausted Ca−L can be recovered using HCl and Ca−L recycled. Moreover, low-cost lignite is a promising carbon support for the future synthesis of different value-added products.

Revisiting the Complexation of Cm(III) with Aqueous Phosphates: What Can We Learn from the Complex Structures Using Luminescence Spectroscopy and Ab Initio Simulations?

The coordination chemistry of Cm(III) with aqueous phosphates was investigated by means of laser-induced luminescence spectroscopy and ab initio simulations. For the first time, in addition to the presence of Cm(H2PO4)2+, the formation of Cm(H2PO4)2+ was unambiguously established from the luminescence spectroscopic data collected at various H+ concentrations (-log10 [H+] = 2.52, 3.44, and 3.65), ionic strengths (0.5-3.0 mol·L-1 NaClO4), and temperatures (25-90 °C). Complexation constants for both species were derived and extrapolated to standard conditions using the specific ion interaction theory. The molal enthalpy ΔRHm0 and molal entropy ΔRSm0 of both complexation reactions were derived using the integrated van't Hoff equation and indicated an endothermic and entropy-driven complexation. For the Cm(H2PO4)2+ complex, a more satisfactory description could be obtained when including the molal heat capacity term. While monodentate binding of the H2PO4- ligand(s) to the central curium ion was found to be the most stable configuration for both complexes in our ab initio simulations and luminescence lifetime analyses, a different temperature-dependent coordination to hydration water molecules could be deduced from the electronic structure of the Cm(III)-phosphate complexes. More precisely, where the Cm(H2PO4)2+ complex could be shown to retain an overall coordination number of 9 over the entire investigated temperature range, a coordination change from 9 to 8 was established for the Cm(H2PO4)2+ species with increasing temperature.

Carbon‐ZnO Composite Synthesized from ZIF‐8 Depositing Vegetable Biomass for Efficient Removal of Phosphate from Aqueous Solution

AbstractIn order to combine the advantage of biochar and zeolitic imidazolate frameworks (ZIF‐8), the carbon‐ZnO composite were prepared by calcination the hybrid of two vegetable biomasses (rape, Ra, Brassia campestris L. and Chinese cabbage, Cc, Brassica rapa pekinensis) and ZIF‐8. The characterization results showed Cc‐ZnO and Ra‐ZnO had the random, irregular and hollow structure. The adsorptive removal of carbon‐ZnO composite for aqueous phosphate was performed using batch equilibrium method. Both Cc‐ZnO and Ra‐ZnO showed higher adsorption capacities than the pristine biochars and ZIF‐8, and Ra‐ZnO can remove phosphate quickly within 60 min. The adsorption kinetic data were consistent to the pseudo‐second‐order equation and the isothermal data followed the Langmuir and Freundlich models. The main interactions of phosphate adsorption by Cc‐ZnO and Ra‐ZnO were electrostatic attraction and surface complexation. The above results indicated the carbon‐ZnO composite could be used as a promising adsorbent to treat wastewater containing phosphate.

Phosphate Elimination and Recovery Lightweight (PEARL) membrane: A sustainable environmental remediation approach

Aqueous phosphate pollution can dramatically impact ecosystems, introducing a variety of environmental, economic, and public health problems. While novel remediation tactics based on nanoparticle binding have shown considerable promise in nutrient recovery from water, they are challenging to deploy at scale. To bridge the gap between the laboratory-scale nature of these nanostructure solutions and the practical benchmarks for deploying an environmental remediation tool, we have developed a nanocomposite material. Here, an economical, readily available, porous substrate is dip coated using scalable, water-based processes with a slurry of nanostructures. These nanomaterials have tailored affinity for specific adsorption of pollutants. Our Phosphate Elimination and Recovery Lightweight (PEARL) membrane can selectively sequester up to 99% of phosphate ions from polluted waters at environmentally relevant concentrations. Moreover, mild tuning of pH promotes at will adsorption and desorption of nutrients. This timed release allows for phosphate recovery and reuse of the PEARL membrane repeatedly for numerous cycles. We combine correlative microscopy and spectroscopy techniques to characterize the complex microstructure of the PEARL membrane and to unravel the mechanism of phosphate sorption. More broadly, through the example of phosphate pollution, this work describes a platform membrane approach based on nanostructures with specific affinity coated on a porous structure. Such a strategy can be tuned to address other environmental remediation challenges through the incorporation of other nanomaterials.

Control of retention mechanisms on an octadecyl-bonded silica column using ionic liquid-based mobile phase in analysis of cytostatic drugs by liquid chromatography

This study assesses the potential of using ionic liquids (ILs) as mobile phase additives to control the retention mechanism of four cytostatic drugs: doxorubicin hydrochloride (DOX), epirubicin hydrochloride (EPI), daunorubicin hydrochloride (DAU) and idarubicin hydrochloride (IDA). Chromatographic separations were performed on a C18 analytical column (Discovery C18 150 × 4.6 mm, 5 µm) using six IL anions and four methyl-substituted IL cations with different alkyl chain lengths (alone or with the additional methyl group on the aromatic ring), or with an allyl group added as a cationic substituent. Thus, a total of 17 different ILs were assessed. The aqueous formic acid solution and phosphate buffer were used to compare how mobile phase composition affected the behavior of the analyzed cytostatic agents in the presence of ILs. In addition, the impacts of IL concentration, phosphate buffer concentration, and phosphate buffer pH on the final results were also considered. The ability to change analyte retention without negatively impacting peak shape or analytical efficiency was also controlled via the tailing factor and number of theoretical plates. Based on the results, the tested ILs were classified as either effective or ineffective mobile phase additives for separation of anthracyclines and identification by LC-FL technique.

Montmorillonite-iron crosslinked alginate beads for aqueous phosphate removal

Phosphate runoff from agriculture fields leads to eutrophication of the water bodies with devastating effects on the aquatic ecosystem. In this study, naturally occurring montmorillonite clay-incorporated iron crosslinked alginate biopolymer (MtIA) beads were synthesized and evaluated for aqueous phosphate removal. Batch experiment data showed an efficient phosphate removal (>99%) by the MtIA beads from solutions with different initial phosphate concentrations (1 and 5 mg PO43−-P/L, and 100 μg PO43−-P/L). The kinetic data fitted well into the pseudo-second-order kinetic model indicating chemisorption played an important role in phosphate removal. Based on analyses of results from the Elovich and intra-particulate diffusion models, phosphate removal by the MtIA beads was found to be chemisorption where both film diffusion and intra-particulate diffusion participated. The isotherm studies indicate that MtIA surfaces were heterogeneous, and the adsorption capacity of the beads calculated from Langmuir model was 48.7 mg PO43−-P/g of dry beads which is ~2.3 times higher than values reported for other clay-metal-alginate beads. Electron microscopy (SEM-EDS) data from the beads showed a rough-textured surface which helped the beads achieve better contact with the phosphate ions. Fourier-transform infrared spectroscopy (FTIR) indicated that both iron and montmorillonite clay participated in crosslinking with the alginate chain. The MtIA beads worked effectively (>98% phosphate removal) over a wide pH range of 2–10 making it a robust adsorbent. The beads can potentially be used for phosphate recovery from eutrophic lakes, agricultural run-off, and municipal wastewater.

Green microfluidic liquid-phase microextraction of polar and non-polar acids from urine.

In this work, hippuric acid (log P = 0.5), anthranilic acid (log P = 1.3), ketoprofen (log P = 3.6), and naproxen (log P = 3.0) were simultaneously extracted by a green microfluidic device based on the principles of liquid-phase microextraction (LPME). Different deep eutectic solvents (DESs) were investigated as supported liquid membrane (SLM), and a mixture of camphor and menthol as eutectic solvents in the molar ratio 1:1 was found to be highly efficient for the simultaneous extraction of non-polar and polar acidic drugs. LPME was conducted for 6min per sample. Urine sample was delivered to the system at 1μLmin-1, and target analytes were extracted exhaustively (75-100% recovery) across the DES SLM, and into pure aqueous phosphate buffer pH11.0 delivered as acceptor at 1μLmin-1. The acceptor was analyzed with liquid chromatography-UV detection. Interestingly, the DES enabled extraction of both the polar and non-polar model analytes at the same time; all chemicals were green and non-hazardous, and the chemical waste was less than 1mg per sample.

Facile synthesis of eggshell biochar beads for superior aqueous phosphate adsorption with potential urine P-recovery

Phosphorus (P) uptake from wastewater is a widespread concern due to the concurrent issues of P contamination and deficiency. A corn straw biochar-based eggshell bead composite (CS-E0.25-Ca(b)) was innovatively synthesized via a facile gelation-calcination method for efficient P recovery from urine solutions. Batch adsorption experiments showed that CS-E0.25-Ca(b) fabricated under optimal conditions exhibited a superior adsorption capacity (136.83 mg/g), which was 29.93 and 6.77 times that of pristine biochar (CSBC) and bead without the addition of eggshell respectively. CS-E0.25-Ca(b) exhibited favorable adsorption performance at pH 6.0–9.0 and in the presence of coexisting anion conditions, and showed good mass transfer performance in urine environment. Characterization results indicated that corn straw biochar matrix can lead to porous internal structure, which could facilitate better dispersion of CaO/Ca(OH)2 in eggshell to adhere on CS-E0.25-Ca(b). The comparison of FTIR and XPS analyses revealed that the surface precipitation with Ca-P products of hydroxyapatite (HAP) and amorphous calcium phosphate (ACP) was the predominant mechanism of phosphorus adsorption on CS-E0.25-Ca(b). In the slow-releasing experiment, the urine P-saturated CS-E0.25-Ca(b) displayed controllable and long-term slow-releasing property in neutral solution. Besides, CS-E0.25-Ca(b) after P release displayed favorable adsorption performance for common heavy metals, showing potential extra benefit for remediating heavy metal contaminated soils. All the results suggested that CS-E0.25-Ca(b) can realize superior P uptake from urine, also be potentially qualified as a promising slow-releasing fertilizer for soil P supply.

Electrospun Biomaterials from Chitosan Blends Applied as Scaffold for Tissue Regeneration.

Our objective in this work was to summarize the main results obtained in processing pure chitosan and chitosan/hyaluronan complex in view of biomedical applications, taking advantage of their original properties. In addition, an electrospinning technique was selected to prepare nanofiber mats well adapted for tissue engineering in relation to the large porosity of the materials, allowing an exchange with the environment. The optimum conditions for preparation of purified and stable nanofibers in aqueous solution and phosphate buffer pH = 7.4 are described. Their mechanical properties and degree of swelling are given. Then, the prepared biomaterials are investigated to test their advantage for chondrocyte development after comparison of nanofiber mats and uniform films. For that purpose, the adhesion of cells is studied by atomic force microscopy (AFM) using single-cell force spectroscopy, showing the good adhesion of chondrocytes on chitosan. At the end, adhesion and proliferation of chondrocytes in vitro are examined and clearly show the interest of chitosan nanofiber mats compared to chitosan film for potential application in tissue engineering.

High capacity aqueous phosphate reclamation using Fe/Mg-layered double hydroxide (LDH) dispersed on biochar

Phosphate is a primary plant nutrient, serving integral role in environmental stability. Excessive phosphate in water causes eutrophication; hence, phosphate ions need to be harvested from soil nutrient levels and water and used efficiently. Fe-Mg (1:2) layered double hydroxides (LDH) were chemically co-precipitated and widely dispersed on a cheap, commercial Douglas fir biochar (695 m2/g surface area and 0.26 cm3/g pore volume) byproduct from syn gas production. This hybrid multiphase LDH dispersed on biochar (LDHBC) robustly adsorbed (~5h equilibrium) phosphate from aqueous solutions in exceptional sorption capacities and no pH dependence between pH 1–11. High phosphate Langmuir sorption capacities were found for both LDH (154 to 241 mg/g) and LDH-modified biochar (117 to 1589 mg/g). LDHBC was able to provide excellent sorption performance in the presence of nine competitive anion contaminants (CO32–, AsO43−, SeO42−, NO3–, Cr2O72−, Cl−, F−, SO42−, and MoO42−) and also upon remediating natural eutrophic water samples. Regeneration was demonstrated by stripping with aqueous 1 M NaOH. No dramatic performance drop was observed over 3 sorption-stripping cycles for low concentrations (5 ppm). The adsorbents and phosphate-laden adsorbents were characterized using Elemental analysis, BET, PZC, TGA, DSC, XRD, SEM, TEM, and XPS. The primary sorption mechanism is ion-exchange from low to moderate concentrations (10–500 ppm). Chemisorption and stoichiometric phosphate compound formation were also considered at higher phosphate concentrations (>500 ppm) and at 40 °C. This work advances the state of the art for environmentally friendly phosphate reclamation. These phosphate-laden adsorbents also have potential to be used as a slow-release phosphate fertilizer.

Biofabrication of 3D printed hydroxyapatite composite scaffolds for bone regeneration

Biofabrication has been adapted in engineering patient-specific biosynthetic grafts for bone regeneration. Herein, we developed a three-dimensional (3D) high-resolution, room-temperature printing approach to fabricate osteoconductive scaffolds using calcium phosphate cement (CPC). The non-aqueous CPC bioinks were composed of tetracalcium phosphate, dicalcium phosphate anhydrous, and Polyvinyl butyral (PVB) dissolved in either ethanol (EtOH) or tetrahydrofuran (THF). They were printed in an aqueous sodium phosphate bath, which performs as a hardening accelerator for hydroxyapatite formation and as a retainer for 3D microstructure. The PVB solvents, EtOH or THF, affected differently the slurry rheological properties, scaffold microstructure, mechanical properties, and osteoconductivity. Our proposed approach overcomes limitations of conventional fabrication methods, which require high-temperature (>50 °C), low-resolution (>400 μm) printing with an inadequate amount of large ceramic particles (>35 μm). This proof-of-concept study opens venues in engineering high-resolution, implantable, and osteoconductive scaffolds with predetermined properties for bone regeneration.

Effect of filter extraction solvents on the measurement of the oxidative potential of airborne PM2.5

Solvent extraction of PM2.5 samples collected on the filter is a preliminary step for assessing the PM2.5 oxidative potential (OP) using cell-free assays, as the dithiothreitol (DTT) and the ascorbic acid (AA) assays. In this study, we evaluated the effect of the solvent choice by extracting ambient PM2.5 samples with different solvents: methanol, as organic solvent, and two aqueous buffers, i.e., phosphate buffer (PB) and Gamble’s solution (G), as a lung fluid surrogate solution. Both the measured volume-based OPVDTT and OPVAA responses varied for the different extraction methods, since methanol extraction generated the lowest values and phosphate buffer the highest. Although all the tested solvents produced intercorrelated OPVDTT values, the phosphate buffer resulted the most useful for OPDTT assessment, as it provided the most sensible measure (nearly double values) compared with other extractions. The association of the measured OPV values with PM chemical composition suggested that oxidative properties of the investigated PM2.5 samples depend on both transition metals and quinones, as also supported by additional experimental measurements on standard solutions of redox-active species.

Polyethylene Glycol Coated Magnetic Nanoparticles: Hybrid Nanofluid Formulation, Properties and Drug Delivery Prospects.

Magnetic nanoparticles (MNPs) are widely used materials for biomedical applications owing to their intriguing chemical, biological and magnetic properties. The evolution of MNP based biomedical applications (such as hyperthermia treatment and drug delivery) could be advanced using magnetic nanofluids (MNFs) designed with a biocompatible surface coating strategy. This study presents the first report on the drug loading/release capability of MNF formulated with methoxy polyethylene glycol (referred to as PEG) coated MNP in aqueous (phosphate buffer) fluid. We have selected MNPs (NiFe2O4, CoFe2O4 and Fe3O4) coated with PEG for MNF formulation and evaluated the loading/release efficacy of doxorubicin (DOX), an anticancer drug. We have presented in detail the drug loading capacity and the time-dependent cumulative drug release of DOX from PEG-coated MNPs based MNFs. Specifically, we have selected three different MNPs (NiFe2O4, CoFe2O4 and Fe3O4) coated with PEG for the MNFs and compared their variance in the loading/release efficacy of DOX, through experimental results fitting into mathematical models. DOX loading takes the order in the MNFs as CoFe2O4 > NiFe2O4 > Fe3O4. Various drug release models were suggested and evaluated for the individual MNP based NFs. While the non-Fickian diffusion (anomalous) model fits for DOX release from PEG coated CoFe2O4, PEG coated NiFe2O4 NF follows zero-order kinetics with a slow drug release rate of 1.33% of DOX per minute. On the other hand, PEG coated NiFe2O4 follows zero-order DOX release. Besides, several thermophysical properties and magnetic susceptibility of the MNFs of different concentrations have been studied by dispersing the MNPs (NiFe2O4, CoFe2O4 and Fe3O4) in the base fluid at 300 K under ultrasonication. This report on the DOX loading/release capability of MNF will set a new paradigm in view that MNF can resolve problems related to the self-heating of drug carriers during mild laser treatment with its thermal conducting properties.

Lignite, thermally-modified and Ca/Mg-modified lignite for phosphate remediation

Aqueous phosphate uptake is needed to reduce global eutrophication. Negatively charged adsorbent surfaces usually give poor phosphate sorption. Chemically- and thermally-modified lignite (CTL) was prepared by impregnating low-cost lignite (RL) with Ca2+ and Mg2+ cations, basified with KOH (pH ̴ 13.9), followed by a 1 h 600 °C pyrolysis under nitrogen. CTL has a positive surface (PZC = 13) due to basic surface Ca and Mg compounds, facilitating the aqueous phosphate uptake. CaCO3, MgO, Ca(OH)2, and Mg(OH)2 surface phases with 0.22 μm particle sizes were verified by XRD, XPS, SEM, TEM, and EDX before and after phosphate uptake. Higher amounts of these mineral phases promoted more CTL phosphate uptake than raw lignite (RL) and thermally treated lignite (TL) without Ca/Mg modification. Phosphorous uptake by Ca2+/Mg2+ occurs not by classic adsorption but by stochiometric precipitation of Mg3(PO4)2, MgHPO4, Ca3(PO4)2, and CaHPO4. This offers the potential of substantial uptake capacities. CTL's phosphate removal is pH-dependent; the optimum pH was 2.2. Water-washed CTL exhibited a maximum Langmuir phosphate uptake capacity of 15.5 mg/g at pH 7, 6 and 14 times higher than that of TL and RL, respectively (particle size <150 μm, adsorbent dose 50 mg, 25 mL of 25–1000 ppm phosphate concentration, 24 h, 25 °C). The unwashed CTL exhibited a maximum Langmuir phosphate removal capacity (80.6 mg/g), 5.2-times greater than the washed CTL (15.5 mg/g). Insoluble Ca2+ and Mg2+ phosphates/hydrophosphate particles dominated CTL's phosphate removal. Phosphates were recovered from both exhausted unwashed and washed CTL better in HCl than in NaOH. P-laden washed CTL exhibited a slow phosphate leaching rate under initial pH of 6.5–7.5 (52–57% over 20 days) after phosphate uptake, indicating it could serve as a slow-release fertilizer. Unwashed CTL retained more phosphates than washed CTL (cumulative qe for 4 cycles = 391.8 mg/g vs 374.7 mg/g) and potentially improves soil fertility more.

In vitro kinetic release study of ketoprofen enantiomers from alginate metal complexes

BackgroundTo explore the release behavior of ketoprofen enantiomers from alginate-metal-complexes. Five mathematical models of drug release kinetics were investigated.ResultsBeads of alginate-metal complexes, loaded with racemic ketoprofen, were prepared by the ionotropic method. Divalent (Ca, Ba, Zn) and trivalent (Fe, Al) metals were used in the preparation of single-metal and mixed-metal alginate complexes. In vitro release experiments were carried out in an aqueous phosphate buffer medium at pH = 7.4. The concentrations of ketoprofen released enantiomers were determined using chiral HPLC technique. The obtained data were used to simulate the release kinetic of ketoprofen enantiomers using various mathematical models. The Korsmeyer-Peppas model was the best fit for Ca, Al, and Fe beads. Moreover, alginate-iron beads tend to release the drug faster than all other cases. In contrast, the drug release for alginate-barium complex was the slowest. The presence of barium in alginate mixed-metal complexes reduced ketoprofen release in the case of Fe and Zn, while it increased the release in the case of Al complex.ConclusionIn all the studied cases, ketoprofen showed very slow release for both enantiomers over a period exceeded 5 h (10 days in some cases). The release rate modification is possible using different multivalent metals, and it is also feasible by using two different metals for congealing either consecutively or simultaneously.

Metamaterial-Inspired Microwave Sensor for Detecting the Concentration of Mixed Phosphate and Nitrate in Water

This is the first report of the construction of a metamaterial-inspired microwave sensor for concentration measurements of aqueous phosphate, nitrate, and mixed phosphate and nitrated solutions. The design of the proposed device is based on a microstrip line (ML) coupled square complementary split-ring resonator (SCSRR), which is squeezed to the narrow width of the slot in the active area. Phosphate, nitrate, and mixed phosphate and nitrate with different liquid sample concentrations inside a cylindrical tube modify the transmission coefficient ( S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> ) and resonance frequency ( f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ) of the SCSRR. The method utilizes a microwave frequency in the range of 1.0-1.2 GHz with different sample concentrations ranging from 0 to 1 mg/ml. The change of electromagnetic properties can be used to monitor the phosphate, nitrate, and mixed phosphate and nitrate concentrations. Principle component analysis (PCA) is used for sample classification. This chemical sensing concept is potentially useful in biochemistry, medicine, agriculture, and the environment.

Flow Process Development and Optimization of A Suzuki-Miyaura Cross Coupling Reaction using Response Surface Methodology

A custom-made tubular flow reactor was utilized to develop a mathematical model and optimize the Suzuki-Miyaura cross coupling reaction. In this study, the experimentation was designed and executed through the statistical design of experiments (DoE) approach via response surface methodology. The effect of molar ratios of phenylboronic acid (1) and 4-bromophenol (2), temperature, the catalyst tetrakis(triphenylphosphine)palladium, and equivalence of aqueous tripotassium phosphate was studied in detail. The flow reactor profile was in good agreement with batch conditions and significant improvements to the overall reaction time and selectivity towards desired [1-1-biphenyl]-4-ol (3) was achieved. The Suzuki coupling reaction in batch condition would take on an average of 4 to 6 hours to complete, which was effectively accomplished in 60 to 70 minutes in this tubular reactor setup and could be operated continuously. The reaction model is in good agreement with the reaction conditions. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Trace Co2+ coupled with phosphate triggers efficient peroxymonosulfate activation for organic degradation

Cobalt-mediated activation of peroxymonosulfate (PMS) has been widely used to remove the refractory organic pollutants from contaminated waters. However, the residual cobalt usually at a trace level inevitably brings about secondary pollution to be disposed of. In this study we found that the presence of phosphate could trigger a more efficient catalytic activation of PMS at trace Co2+ dosages (0.17–1.7 μM). Fast degradation of atrazine (ATZ) was observed in the Co2+/PMS/phosphate system, with the pseudo first-order kinetic rate constant as high as 5.4 and 15.4 times that in Co2+/PMS and phosphate/PMS systems respectively under otherwise similar conditions. The presence of phosphate promoted the production of sulfate radical (SO4·-), accompanying the enhanced formation of by-product 1O2 simultaneously. Using a competition reaction kinetics approach, the contribution of SO4·- to ATZ oxidation was determined as 96.5%, suggesting that SO4·- was the main reactive species responsible for ATZ removal. Such favorable effect was partially ascribed to the specific ligand structure of six coordination structure between phosphate and cobalt, which facilitated electron transfer in the CoIII/CoII reduction. In addition, it was dependent upon the aqueous phosphate levels, and low level (< 0.5 mM) was insufficient to drive the CoIII/CoII cycle, whereas the higher level (> 15 mM) showed negative effect since the excessive phosphate could quench SO4·- and·OH. This study is believed to advance the fundamental understanding of the ligand effect on the cobalt-mediated sulfate radicals-based advanced oxidation process.

Energy‐Efficient Preparation Method of Water‐Swellable Starch Phosphate Carbamate Particles

AbstractA simple preparation method for highly water‐swellable starch phosphate carbamate (SPC) particles is proposed. In this method, a mixture of starch, urea and aqueous phosphate solution is heated in the form of gel particles under ambient pressure. The physical properties of SPC and the reaction kinetics are compared with those of the conventional method in which the thermal reaction is carried out in the form of paste. The reaction mechanism is studied by elemental analysis, Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy. The high efficiency of the proposed method and the excellent balance of water absorption capacity and shear modulus of the product are attractive from an industrial point of view.