Efficient and selective upcycling of waste polylactic acid into acetate using nickel selenide

The conversion of waste polylactic acid(PLA)plastics into high-value-added chemicals through electrochemical methods is a promising and sustainable approach.However,developing efficient and highly selective catalysts for lactic acid oxidation reaction(LAOR)and understanding the reaction process are challenging.Here,we report the electrooxidation of waste PLA to acetate at a high current density of 100 mA cm-2 with high Faraday efficiency(~95%)and excellent stability(>100 h)over a nickel selenide nanosheet catalyst.In addition,a total Faraday efficiency of up to 190%was achieved for carboxylic acids,including acetic acid and formic acid,by coupling with the cathodic CO_(2) reduction reaction.In situ experimental results and theoretical simulations revealed that the catalytic activity center of LAOR was dynamically formed NiOOH species,and the surface-adsorbed SeO_(x) species accelerated the formation of Ni~(3+)species,thus promoting catalytic activity.The mechanism of lactic acid electrooxidation was further elucidated.Lactic acid was dehydrogenated to produce pyruvate first and then formed CH_3CO due to preferential C-C bond cleavage,resulting in the presence of acetate.This work demonstrated a sustainable method for recycling waste PLA and CO_(2) into high-value-added products.

Dancing bubble sonoluminescence in phosphoric acid solution

Sonoluminescence is more distinctly observed in phosphoric and sulfuric acid,which exhibit high viscosity and lower vapor pressures relative to water.Within an 85-wt%phosphoric acid solution saturated with argon(Ar),variations in the light-emitting regimes of bubbles were noted to correspond with increments in the driving acoustic intensity.Specifically,the bubbles were observed to perform a dance-like motion 2 cm below the multi-bubble sonoluminescence(MBSL)cluster,traversing a 25-mm^(2) grid during the camera exposure period.Spectral analysis conducted at the beginning of the experiment showed a gradual attenuation of CN(B^(2)S–X^(2)S)emission concurrent with a strengthening of Ar(4p–4s)atom emission lines.The application of a theoretical temperature model to the spectral data revealed that the internal temperature of the bubbles escalates swiftly upon their implosion.This study is instrumental in advancing the comprehension of the underlying mechanisms of sonoluminescence and in the formulation of a dynamic model for the behavior of the bubbles.

Poly(p-coumaric acid)nanoparticles alleviate temporomandibular joint osteoarthritis by inhibiting chondrocyte ferroptosis

Oxidative stress and inflammation are key drivers of osteoarthritis(OA)pathogenesis and disease progression.Herein we report the synthesis of poly(p-coumaric)nanoparticles(PCA NPs)from p-courmaic acid(p-CA),a naturally occurring phytophenolic acid,to be a multifunctional and drug-free therapeutic for temporomandibular joint osteoarthritis(TMJOA).Compared to hyaluronic acid(HA)that is clinically given as viscosupplementation,PCA NPs exhibited long-term efficacy,superior anti-oxidant and anti-inflammatory properties in alleviating TMJOA and repairing the TMJ cartilage and subchondral bone in a rat model of TMJOA.Notably,TMJ repair mediated by PCA NPs could be attributed to their anti-oxidant and anti-inflammatory properties in enhancing cell proliferation and matrix synthesis,while reducing inflammation,oxidative stress,matrix degradation,and chondrocyte ferroptosis.Overall,our study demonstrates a multifunctional nanoparticle,synthesized from natural p-coumaric acid,that is stable and possess potent antioxidant,anti-inflammatory properties and ferroptosis inhibition,beneficial for treatment of TMJOA.

Edaravone-loaded poly(amino acid) nanogel inhibits ferroptosis for neuroprotection in cerebral ischemia injury

Neurological injury caused by ischemic stroke is a major cause of permanent disability and death. The currently available neuroprotective drugs fail to achieve desired therapeutic efficacy mainly due to short circulation half-life and poor blood−brain barrier (BBB) permeability. For that, an edaravone-loaded pH/glutathione (pH/GSH) dual-responsive poly(amino acid) nanogel (NG/EDA) was developed to improve the neuroprotection of EDA. The nanogel was triggered by acidic and EDA-induced high-level GSH microenvironments, which enabled the selective and sustained release of EDA at the site of ischemic injury. NG/EDA exhibited a uniform sub-spherical morphology with a mean hydrodynamic diameter of 112.3 ± 8.2 nm. NG/EDA efficiently accumulated at the cerebral ischemic injury site of permanent middle cerebral artery occlusion (pMCAO) mice, showing an efficient BBB crossing feature. Notably, NG/EDA with 50 µM EDA significantly increased neuron survival (29.3%) following oxygen and glucose deprivation by inhibiting ferroptosis. In addition, administering NG/EDA for 7 d significantly reduced infarct volume to 22.2% ± 7.2% and decreased neurobehavioral scores from 9.0 ± 0.6 to 2.0 ± 0.8. Such a pH/GSH dual-responsive nanoplatform might provide a unique and promising modality for neuroprotection in ischemic stroke and other central nervous system diseases.

Synergism of Zinc Oxide/Organoclay-Loaded Poly(lactic acid) Hybrid Nanocomposite Plasticized by Triacetin for Sustainable Active Food Packaging

The synergistic effect of organoclay(OC)and zinc oxide(ZnO)nanoparticles on the crucial properties of poly(lactic acid)(PLA)nanocompositefilms was systematically investigated herein.After their incorporation into PLA via the solvent casting technique,the water vapor barrier property of the PLA/OC/ZnOfilm improved by a maximum of 86%compared to the neat PLAfilm without the deterioration of Young’s modulus or the tensile strength.Moreover,thefilm’s self-antibacterial activity against foodborne pathogens,including gram-negative(Escherichia coli,E.coli)and gram-positive(Staphylococcus aureus,S.aureus)bacteria,was enhanced by a max-imum of approximately 98–99%compared to the neat PLAfilm.Furthermore,SEM images revealed the homo-geneous dispersion of both nano-fillers in the PLA matrix.However,the thermal stability of thefilm decreased slightly after the addition of the OC and ZnO.Thefilm exhibited notable light barrier properties in the UV-Vis range.Moreover,the incorporation of a suitable biodegradable plasticizer significantly decreased the Tg and notably enhanced theflexibility of the nanocompositefilm by increasing the elongation at break approxi-mately 1.5-fold compared to that of the neat PLAfilm.This contributes to its feasibility as an active food packa-ging material.

Poly(lactic acid)-aspirin microspheres prepared via the traditional and improved solvent evaporation methods and its application performances

Drug-loaded microspheres are significant for the development of modern pharmaceutical products. It is well known that the taken of aspirin for long-term increases the risk of serious gastrointestinal complications, therefore a controllable delivery of aspirin is of importance to lighten those side effects. In this work, poly(lactic acid)(PLA) was chosen as the carrier to prepare PLA-aspirin microspheres by using the traditional and the improved solvent evaporation methods. It was found that no matter which experimental condition was, the encapsulation efficiency of aspirin was higher by using the improved method than that of the traditional method. Specifically, when the concentration of polyvinyl alcohol = 1%(mass),the polymer concentration = 1:20, the oil/water rate = 1:2.5, PLA-aspirin microspheres were obtained via the improved method with a high yield of 82.83%(mass) and an encapsulation efficiency of 44.09%. PLAaspirin microspheres were then prepared continuously using the improved method, which further enhanced the encapsulation efficiency to 54.56%. Approximate 85% aspirin released from microspheres within 7 days. Obvious degradation which was represented by reduction on hardness was observed by soaking microspheres in PBS for 60 days. This work is of interest because it provides a continuous route to prepare PLA-aspirin microspheres continuously with a high drug encapsulation efficiency.

Intensified reactive extraction of 4-hydroxypyridine with di(2-ethylhexyl) phosphoric acid in 1-octanol by using tributyl phosphate

The efficient separation of amphoteric organic compounds from dilute solutions is of great importance in the industrial field. In the present work, the reactive extractions of 4-hydroxypyridine(4-HP) with tributyl phosphate(TBP), di(2-ethylhexyl) phosphoric acid(D2EHPA) and TBP + D2EHPA dissolved in 1-octanol were investigated, respectively. The influences of the initial concentrations of TBP, D2EHPA and TBP + D2EHPA on distribution ratio(D) were discussed, as well as the reactive extraction mechanism were proposed. The obvious intensification effect was observed when the mixture of TBP and D2EHPA was used as extractant. The best extraction conditions were found to be of the molar ratio of D2EHPA and TBP at 2:1 and the equilibrium aqueous pH at 3.50-4.50. D values increased with the increase of the total concentration of TBP and D2EHPA in 1-octanol. Especially, the analysis on the extraction mechanisms clearly indicate(i) TBP in 1-octanol shows negligible reactive extraction toward 4-HP,(ii) D2EHPA in 1-octanol exhibits moderate extraction effect by forming 4-HP:D2EHPA(1:1) and 4-HP:2D2EHPA(1:2) type complexes, while(iii) D2EHPA in TBP/1-octanol demonstrates the maximum distribution ratio with the 4-HP:D2EHPA(1:1) type complex domination. The discussion provides new insights on the mechanism and opens a new way for the intensified extraction of amphoteric organic compounds by using the mixture of multiple extractants in the diluent.

High-performance and robust high-temperature polymer electrolyte membranes with moderate microphase separation by implementation of terphenyl-based polymers

Acid loss and plasticization of phosphoric acid(PA)-doped high-temperature polymer electrolyte membranes(HT-PEMs)are critical limitations to their practical application in fuel cells.To overcome these barriers,poly(terphenyl piperidinium)s constructed from the m-and p-isomers of terphenyl were synthesized to regulate the microstructure of the membrane.Highly rigid p-terphenyl units prompt the formation of moderate PA aggregates,where the ion-pair interaction between piperidinium and biphosphate is reinforced,leading to a reduction in the plasticizing effect.As a result,there are trade-offs between the proton conductivity,mechanical strength,and PA retention of the membranes with varied m/p-isomer ratios.The designed PA-doped PTP-20m membrane exhibits superior ionic conductivity,good mechanical strength,and excellent PA retention over a wide range of temperature(80–160°C)as well as satisfactory resistance to harsh accelerated aging tests.As a result,the membrane presents a desirable combination of performance(1.462 W cm^(-2) under the H_(2)/O_(2)condition,which is 1.5 times higher than that of PBI-based membrane)and durability(300 h at 160°C and 0.2 A cm^(-2))in the fuel cell.The results of this study provide new insights that will guide molecular design from the perspective of microstructure to improve the performance and robustness of HT-PEMs.

The Structure Development of Cellulose Dissolved in the Phosphoric Acid/Polyphosphoric Acid Solvent

Cellulose,being as the most abundant nature polymer material and the most promising oil substitute,attracts more and more interests.A new cellulose dissolution system,phosphoric acid(PA)/polyphosphoric acid(PPA) solvent,was investigated in this study.It had been found that a larger cellulose solid content could be dissolved quickly in a hypothermic situation.By evaluating the stability of regenerated cellulose film and the formation of anisotropic solution,the dissolution behavior of cellulose was investigated.Wide-angle X-ray diffraction(WAXD) and Fourier transform infrared spectroscopy(FT-IR) were employed to characterize the crystalline structure and morphology of regenerated cellulose.The measurement results revealed a transition from cellulose-Ⅰ of raw cellulose to cellulose-Ⅱ of regenerated cellulose and a decrease of crystallinity of cellulose after dissolved.This was attributed to the interaction between cellulose and acid solvent,which leaded to the breakage of cellulose intra-and inter-molecule hydrogen bonds and the conformation change of cellulose C6-OH.Moreover,the formation process of cellulose liquid crystal solution was illustrated by polarized light microscope(PLM).That may be induced by the rearranging movement of the cellulose macromolecular chains.

Removal of manganese from waste water by complexation-ultrafiltration using copolymer of maleic acid and acrylic acid

Copolymer of maleic acid and acrylic acid （PMA-100）, combining with polyvinyl butyral （PVB） ultrafiltration membrane was used for the removal of Mn（II） from waste water by complexation-ultrafiltration. The carboxylic group content of PMA-100 and the rate of complexation reaction were measured. Effects of the mass ratio of PMA-100 to Mn（II） （n）, pH, background electrolyte, etc on the rejection rate （R） and permeate flux （J） were investigated. The results show that carboxylic group content of PMA-100 is 9.5 mmol/g. The complexation of Mn（II） with PMA-100 is rapid and completed within 5 min at pH 6.0. Both R and J increase with pH increasing in the range of 2.5-7.0, and R increases with the increase of n at pH 6.0 while J is little affected. The background electrolyte leads to the decrease of R, and CaCl2 has much greater effect on R than NaCl at the same ionic strength.

Adsorption of Cr(Ⅵ) in Water with Phosphoric Acid Modified and Ordinary Walnut Shells

A comparison between the effects of ordinary walnut shell and phosphoric acid modified walnut shell on adsorption of Cr（Ⅵ） was carried out. The experimental results showed that owing to larger surface void of modified walnut shell its adsorption of Cr（Ⅵ） was better. When the temperature was 35 ℃, adsorbent particle size was 1.0-1.6 mm, shaker shock rate was 200 r/min, and dosage of walnut shell was 0.80 g, the Cr（Ⅵ） removal rate reached 99.4%. The fitting of adsorption isotherm and kinetics model showed that, Langmuir isotherm model could reflect the adsorption process of modified walnut shell; and both the adsorption processes of ordinary and modified walnut shells accorded with the pseudo-second-order kinetic equations.

Antimicrobial Expanded Polytetrafluoroethylene Film Prepared by 3-ray Radiation Induced Grafting of Poly（acrylic acid）

The simultaneous γ-ray-radiation-induced grafting polymerization of acrylic acid on ex- panded polytetrafluoroethylene （ePTFE） film was investigated. It was found that the degree of grafting （DG） of poly（acrylic acid） （PAA） can be controlled by the monomer concentration, absorbed dose, and dose rate under an optimal inhibitor concentration of [Fe2＋]=18 mmol/L. SEM observation showed that the macroporous structure in ePTFE films would be covered gradually with the increase of the DG of PAA. The prepared ePTFE-g-PAA film was im- mersed in a neutral silver nitrate solution to fabricate an ePTFE-g-PAA/Ag hybrid film after the addition of NaBH4 as a reduction agent of Ag＋ to Ag atom. SEM, XRD, and XPS results proved that Ag nanoparticles with a size of several tens of nanometers to 100 nanometers were in situ immobilized on ePTFE film. The loading capacity of Ag nanoparticles could be tuned by the DG of PAA, and determined by thermal gravimetric analysis. The quart- titative antibacterial activity of the obtained ePTFE-g-PAA/Ag hybrid films was measured using counting plate method. It can kill all the Escherichia coli in the suspension in 1 h. Moreover, this excellent antibacterial activity can last at least for 4 h. This work provides a facile and practical way to make ePTFE meet the demanding antimicrobial requirement in more and more practical application areas.

Arsenic removal from contaminated soil using phosphoric acid and phosphate

Laboratory batch experiments were conducted to study arsenic （As） removal from a naturally contaminated soil using phosphoric acid （H3PO4） and potassium dihydrogen phosphate （KHEPO4）. Both H3PO4 and KHEPO4 proved to reduce toxicity of the soil in terms of soil As content, attaining more than 20% As removal at a concentration of 200 mmol/L. At the same time, acidification of soil and dissolution of soil components （Ca, Mg, and Si） resulted from using these two extractants, especially H3PO4. The effectiveness of these two extractants could be attributed to the replacement of As by phosphate ions （PO4^3-）. The function of H3PO4 as an acid to dissolve soil components had little effects on As removal. KH2PO4 almost removed as much As as H3PO4, but it did not result in serious damage to soils, indicating that it was a more promising extractant. The results of a kinetic study showed that As removal reached equilibrium after incubation for 360 rain, but dissolution of soil components, especially Mg and Ca, was very rapid. Therefore dissolution of soil components would be inevitable if As was further removed. Elovich model best described the kinetic data of As removal among the four models used in the kinetic study.

Mechanism and kinetics study on removal of Iron from phosphoric acid by cation exchange resin

Iron element is one of the main impurities in wet-process phosphoric acid and it has a significant impact on the subsequent phosphorus chemical products. This paper studied the feasibility of using Sinco-430 cation exchange resin for iron removal from phosphoric acid. The specific surface area and the total exchange capacity of resin were 8.91 m2·g-1 and 5.18 mmol·g-1, respectively. The sorption mechanism was determined by FTIR and XPS and the results indicated that iron was combined with-SO3 H in resin. The removal process was studied as a function of temperature, H3 PO4 content and mass ratio between resin and solution. The unit mass of resin to remove iron was 0.058 g·g-1 resin when the operating parameters were T = 50 ℃, H3 PO4 content = 27.61 wt%and S/L = 0.1, respectively. Kinetics study demonstrated that pseudo-second-order reaction model fits this study best and the calculated activation energy of overall reaction is 29.10 kJ·mol-1. The overall reaction process was mainly controlled by pore diffusion.

Centrifugal extraction of rare earths from wet-process phosphoric acid

Phosphorite ore is a potential resource of rare earths （RE） as well as phosphate; therefore, the recovery of RE from wet-process phosphoric acid （WPA） is promising. This study investigated the influence of rotational speed, extractant concentration, flow ratio and phase contact time on the centrifugal extraction of RE from WPA and the separation of RE from impurities. The results indicate that higher rotational speed, higher extractant concentration and larger flow ratio are beneficial to the extraction of RE and impurities from phosphoric acid. It is found that the phase contact time for efficiently extracting RE and that for iron are of great difference, which provides an effective method for separating RE from iron using the non-equilibrium extraction process in centrifugal contactors. Compared with equilibrium extraction, the separation factor βRE/Fe is enhanced from 0.07 to 17.6.

Synergistic extraction of rare earth by mixtures of 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester and di-(2-ethylhexyl) phosphoric acid from sulfuric acid medium

The extraction of Nd^3＋ and Sm^3＋, including the extraction and stripping capability as well as the separation effect of Nd^3＋ or Sm^3＋, from a sulfuric acid medium, by mixtures of di-（2-ethylhexyl） phosphoric acid （HDEHP, H2A2（0）） and 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester （HEH/EHP, H2L2（0）） were studied. The distribution ratios and synergistic coefficients of Nd^3＋ and Sm^3＋ in different acidities were also determined. A synergistic extractive effect was found when HDEHP and HEH/EHP were used as mixed extractants for Sm^3＋ or Nd^3＋. The chemical compositions of the extracted complex were determined as Nd.（HA2）2-HL2 and Sm.（HA2）2-HL2. The extraction equilibrium constants, enthalpy change, and entropy change of the extraction reaction were also determined.

Insight into the formation mechanism of levoglucosenone in phosphoric acid-catalyzed fast pyrolysis of cellulose

The catalytic fast pyrolysis of cellulose impregnated with phosphoric acid (H3PO4) offers a promising method for the selective production of levoglucosenone (LGO),a valuable anhydrosugar product.However,the fundamental mechanism for selective LGO formation is unclear.Herein,quantum chemistry calculations and catalytic fast pyrolysis experiments were performed to reveal the formation mechanism of LGO in H3PO4-catalyzed cellulose pyrolysis.H3PO4 significantly decreased the energy barriers of the pyrolytic reactions and altered the competitiveness of the LGO formation pathways,promoting LGO formation.Through different pathways in the non-catalytic and H3P04-catalyzed conditions,LGO is mainly produced from the primary decomposition of glucose units of cellulose and secondary conversion of levoglucosan.The major catalytic formation pathways of LGO comprise similar reactions,with dehydration at the 3-OH+2-H site as the rate-determining step.Importantly,secondary conversion of 1,4;3,6-dianhydro-α-D-glucopyranose is not feasible for LGO formation,in contrast to previous reports.In addition,a high degree of polymerization is beneficial for the selectivity of LGO formation in the catalytic process,because the glycosidic bond is important for the formation of the bicyclic structure (1,5-and1,6-acetal rings).

Synthesis of the Biomimetic Polymer: Aliphatic Diamine and RGDS Modified Poly(d,l-lactic acid)

A novel poly（d, /-lactic acid） （PDLLA） based biomimetic polymer was synthesized by grafting maleic anhydride, butanediamine and arg-gly-asp-ser （RGDS） peptides onto the backbone of PDLLA, aiming to overcome the acidity and auto-accelerating degradation of PDLLA during degradation and to improve its biospecificity and biocompatibility. The synthetic copolymer was characterized by FTIR, ^13C NMR and amino acid analyzer （AAA）.

CLAY CATALYZED SYNTHESIS OF BIO-DEGRADABLE POLY(GLYCOLIC ACID)

Glycolic acid was polymerized under vacuum in the presence and absence of nano sized clay.The added clay catalyzed the condensation polymerization which can be confirmed by recording FTIR spectroscopy and intrinsic viscosity (Ⅳ)values.The relative intensity of C=O/CH is increased while increasing the amount of clay.DSC showed the appearance of multiple endotherms of poly(glycolic acid).TGA showed the percentage weight residue remain above 750℃for polymer-nano composite system was 21% and hence proved the fl...

Preparation and properties of short natural fiber reinforced poly(lactic acid) composites

The natural fiber/poly(lactic acid) (PLA) composites were prepared with ramie and jute short fiber as reinforcement and PLA as matrix. The mechanical and thermal properties of the composites were investigated. The results show that the properties of the composites are better than those of plain PLA. When the content of the fiber is 30%, the composites can get the best mechanical properties. The dynamic mechanical analysis results show that the storage moduli of the PLA/ramie and PLA/jute composites increase with respect to the plain PLA. The Vicat softening temperature of the composites is greatly higher than that of PLA. The results of thermogravimetric analysis show that adding fiber to the PLA matrix can improve the degradation temperature of PLA.