Sodium Persulfate Research Articles

Effects of sedimentary organic matter degradation and structure on nonylphenol degradation by sodium persulfate

The structure and constituents of sedimentary organic matter (SOM) in the degradation of benzene ring-14C labeled 4-nonylphenol (14C-NP) by sodium persulfate (Na2S2O8) were investigated. Na2S2O8 mineralized over 84 % of 14C-NP to 14CO2, and no parent unlabeled 4-nonylphenol (NP) compounds were detected in the water-soluble/supernatant phase or extractable residues. Organic carbon (OC) was sequentially separated from six sediment samples collected from the Pearl River (BET), estuary (GSD), continental shelf (S11 and S21), and deep sea (M9 and M10). Demineralized OC (DM), unstable OC (USOC), nonhydrolyzable OC (NHC), and resistant OC (ROC) were obtained and characterized using solid-state 13C nuclear magnetic resonance (SS-NMR). The correlations among USOC, NHC, and the degradation kinetic constant of 14C-NP (kNP) were significant (R2 > 0.86, p < 0.01), indicating that USOC and NHC were the main factors controlling 14C-NP degradation. SOM structure and constituent analyses indicated that O-alkyl C + OCH3/NCH C + COO/NC=O C and carbohydrate + protein were positively related to Ln(kNP) (R2 > 0.72, p < 0.05) because these structures were unstable. However, the stable structures (Alkyl C and Arom CC) and constituents (sporopollenin, algaenan, and char) hindered 14C-NP degradation because they were negatively related to Ln(kNP) (R2 > 0.81, p < 0.05). The OC removal rate was positively correlated with 14C-NP degradation (R2 > 0.86, p < 0.01), indicating that the NP was primarily degraded in parallel with the breakdown of SOM. Stoichiometric analysis showed that Na2S2O8 effectively oxidized over 58 % of the OC to CO2, and the electron transfer efficiency was 17.2–69.5 %. This study is the first to emphasize the importance of SOM degradation, structure, and constituents in the degradation of NP by persulfate.

Detection and analysis of moving reaction boundary-based electrophoresis distance using smartphone images

Electrophoresis titration (ET) based on the moving reaction boundary (MRB) theory can detect the analyte contents in different samples by converting content signals into distance signals. However, this technique is only suitable for on-site qualitative testing, and accurate quantification relies on complex optical equipment and computers. Hence, applying this method to real-time point-of-care testing (POCT) is challenging. In this study, we developed a smartphone-based ET system based on a visual technique to achieve real-time quantitative detection. First, we developed a portable quantitative ET device that can connect to a smartphone; this device consisted of five components, namely, an ET chip, a power module, a microcontroller, a liquid crystal display screen, and a Bluetooth module. The device measured 10 cm×15 cm×2.5 cm, weighed 300 g, and was easy to hold. Thus, it is suitable for on-site testing with a run time of only 2-4 min. An assistant mobile software program was also developed to control the device and perform ET. The colored electrophoresis boundary can be captured using the smartphone camera, and quantitative detection results can be obtained in real time. Second, we proposed a quantitative algorithm based on ET channels. The software was used to recognize the boundary migration distance of three channels, a standard curve based on two given contents of the standards was established using the two-point method, and the content of the test sample was calculated. Human serum albumin (HSA) and uric acid (UA) were used as a model protein and biosample, respectively, to test the performance of the detection system. For HSA detection, different HSA solutions were mixed with a polyacrylamide gel (PAG) stock solution, phenolphthalein was added as an indicator, and sodium persulfate and tetramethyl ethylenediamine (TEMED) were used to promote polymerization to form a gel. For UA detection, agarose gel was filled into the ET channel, the UA sample, urate oxidase, and leucomalachite green were added into the anode cell and incubated for 20 min. ET was then performed. The fitting goodness (R2) values of HSA and UA were 0.9959 and 0.9935, respectively, with a linear range of 0.5-35.0 g/L and a log-linear range of 100-4000 μmol/L. The limits of detection for HSA and UA were 0.05 g/L and 50 μmol/L, respectively, and the corresponding relative standard deviations (RSDs) were not greater than 2.87% and 3.21%, respectively. These results demonstrate that the detection system has good accuracy and sensitivity. Clinical samples collected from healthy volunteers were used as target blood samples, and the developed system was used to measure serum total protein and UA levels. Serum samples from five volunteers were selected, standard curves of total serum protein and UA were established, and the test results were compared with hospital standard testing results. The relative errors for serum total protein and UA were less than 6.03% and 6.21%, respectively, and the corresponding RSDs were less than 3.72% and 5.84%, respectively. These findings verify the accuracy and reliability of the proposed detection system. The smartphone-based ET detection system introduced in this paper presents several advantages. First, it enables the portable real-time detection of total serum protein and UA. Second, compared with traditional ET strategies based on colored boundaries, it does not rely on optical detection equipment or computers to obtain quantitative detection results; as such, it can reduce the complexity of the operation and provide portability and real-time metrics. Third, the detection of two biomarkers, serum total protein and UA, is achieved on the same device, thereby improving the multitarget detection potential of the ET method. These advantages render the developed method a promising detection platform for clinical applications and real-time POCT.

Heterogeneous Activation of Persulfate by Nickel Oxide/Strontium Carbonate Composite for Sulfamethoxazole Degradation in Water

The development of efficient heterogeneous persulfate activators is one of the main research topics in the wastewater treatment area. The present work deals with the heterogeneous activation of sodium persulfate (SPS) using nickel oxide/strontium carbonate (NiO/SrCO3) for the degradation of sulfamethoxazole (SMX), a representative compound from the group of antibiotics. Results showed that NiO/SrCO3 exhibited high performance towards the activation of SPS, leading to SMX elimination in brief time spans. The impact of SPS (25–100 mg/L), NiO/SrCO3 (50–250 mg/L), and SMX (0.25–3.00 mg/L) concentration, and initial pH on the decomposition of SMX was further examined. Experiments were also conducted in real matrices such as secondary effluent and bottled water, revealing the existence of retarding phenomena compared to ultrapure water. This behavior was further investigated with the addition of bicarbonates, chlorides, or humic acid in ultrapure water. It was found that organic matter significantly hampered SMX removal. The role of the main radicals (hydroxyl and sulfate radicals) was determined using appropriate radical traps (methanol and tert-butanol). These quenching experiments combined with the conducted electrochemical measurements revealed that both a radical and a non-radical mechanism contribute to the decomposition of SMX.

A new solvent-free pathway for inducing quaternized lignin-derived high molecular weight polymer

In this work, kraft lignin (KL) was polymerized with vinylbenzyl chloride (VBC) in a molar ratio of 1.8:1 (KL: VBC) using sodium persulfate (Na2S2O8) as an initiator at pH 9–10 and temperature of 80–90 °C for 3 h to produce polymer kraft lignin-g-poly(4-vinylbenzyl chloride) KL-poly(VBC) 1. Then, the grafting reaction was conducted with two different imidazole-based monomers of different side-chain lengths (methyl and n-butyl), namely, 1-methylimidazole (MIM), 1-n-butylimidazole (BIM), which led to the formation of novel polymers, kraft lignin-g-poly(4-vinylbenzyl-1-methylimidazolium chloride) KL-poly(VBC-MIM) 2a and kraft lignin-g-poly(4-vinylbenzyl-1-n-butyl imidazolium chloride) KL-poly(VBC-BIM) 2b. The polymer 2a generated a larger molecular weight polymer with a higher charge density and solubility than polymer 2b since the n-butyl group would cause steric hindrance and weaker monomer to react with intermediate polymer 1 in the second stage. The contact angle analysis confirmed more hydrophilicity of polymer 2a, and elemental analysis confirmed the more successful polymerization of polymer 2a. Applying the generated polymers as flocculants for a kaolin suspension confirmed that polymer 2a had similar performance with commercial cationic polyacrylamide (CPAM) flocculants, even though polymer 2a had a smaller molecular weight. This polymerization offers a promising pathway for generating cationic polymers with excellent performance as a flocculant for suspensions.

Enhancing nitrogen removal from sludge-derived hydrochar via hydrothermal carbonization fortified with advanced oxidation process pretreatment

In order to prepare low-nitrogen hydrochar, this study used sodium persulfate pretreatment coupled with hydrothermal carbonization (HTC) to destroy the sludge structure to release nitrogen-containing substances by free radical. Meanwhile, the effects of sodium persulfate concentration and free radical activation ways on nitrogen transition were also discussed. After the sludge was pretreated with 40 mmol/L sodium persulfate for 3 h under UV/heat synergistic activation, the maximum nitrogen removal efficiency of the hydrochar can reach 60.05 % at 240 °C hydrothermal temperature, which was 20.91 % higher than that of the original sample (39.14 %). Furthermore, in this condition, the ammonia nitrogen and total nitrogen in the aqueous phase reached the highest of 3008 mg/L and 6316 mg/L, respectively. During pretreatment, the persulfate radical (SO4·-) and hydroxyl radical (·OH) were the key to the destruction of the EPS structure, which realized the transfer of nitrogen from the solid to liquid. In addition, the acidic environment generated by the hydrolysis of sodium persulfate promoted the conversion of stubborn proteins to easily decomposed proteins (such as Nitrile-N) and the inhibition of the Maillard reaction. This study supplements relevant theories for the production of low nitrogen hydrochar by pretreating sludge with sodium persulfate.

Degradation of Rhodamine B by CuFe2O4 nanoparticles anchored on montmorillonite as an activator of sodium persulfate

Background: Advanced oxidation techniques based on sulfate radicals can be more effective in dealing with the threats posed by dye wastewater. Methods: In this study, a series of montmorillonite-loaded CuFe2O4 (CFO, 1-CFO/Mt, 2-CFO/Mt, 3-CFO/Mt) composites were prepared using a simple one-pot solvent method for the activation of sodium persulfate (PDS) for the removal of Rhodamine B (RhB) from water. Significant findings: The efficient catalytic activity of the composite catalyst was verified by the degradation of RhB with different systems, and the efficient adsorption of this catalyst accelerated the reaction process of pollutant degradation. The results showed that 97.7% of RhB could be removed within 25 min using 0.3 g/L of 2-CFO/Mt composite catalyst and 1 mM of PDS at the initial pH = 7.5; In addition, the composite catalyst can show good catalytic performance in a wide pH range. It still has high catalytic activity after 3 cycles. The involvement of SO4•−, •OH, 1O2, and O2•− in the degradation of RhB by the 2-CFO/Mt/PDS system was determined by radical quenching experiments as well as EPR test analysis, in which 1O2 dominated in the degradation of RhB by the 2-CFO/Mt/PDS system. Overall, 2-CFO/Mt has significant potential as a PDS activator in the treatment of RhB in water.

Структурно-морфологические свойства вторичного волокна из влагопрочного сырья при мягком размоле. Часть 2. Характеристика волокнистой мелочи

The process of recycled pulp refining is usually associated with a significant change in the morphological characteristics of the secondary fiber and the formation of additional amounts of fines. It is well known that fines have a great impact on the pulp properties, the papermaking process and the quality of the resulting paper. At the same time, the effect of fines both on the paper properties and on the papermaking process depends on the morphological characteristics of the fines. The aim of the study was to evaluate the changes in the morphological characteristics of the fines during gentle low-consistency refining of the recycled pulp. The recycled pulp was obtained from commercial wet-strength tissue paper, consisting of 100 % bleached softwood kraft pulp (BSKP) made from pine (Pinus sylvestris L.). The repulping of wet-strength paper was performed at 60 °C in three ways, namely, repulping with sodium hydroxide (indicated as RP (NaOH)), repulping with sodium hydroxide and sodium persulfate (RP (NaOH + Na2S2O8)), and finally repulping with sodium hydroxide and potassium monopersulfate (RP (NaOH + KHSO5)). Using an optical fiber analyzer, L&amp;W Fiber Tester, it was found that accelerated persulfate and monopersulfate repulping of the wet-strength paper led to an increase in fines content after pulp refining by 0.20…0.28 % on length and by 0.9…1.5 % on number of particles. In addition, some fines were not detected due to the limited resolution of the measuring device. The morphological characteristics of the recycled pulps showed that the studied fines were relatively straight particles (Sl = 93.5...94.0 %) with low length polydispersity ((Ll/Ln) = 1.08...1.09). Fines had a mean slenderness ratio (L/W)l and (L/W)w of about 7, which in some length classes reached 8...9. Taking into account the experimental data on fines length (Ll = 132…134 µm) and fiber width (Wl = 29.7…30.0 µm), as well as SEM images of recycled paper, we can conclude that these particles can form fines-assisted bridges between several close deposited fibers in the fiber network, thus strengthening the paper web. For citation: Penkin A.A., Kazakov Y.V. Changes in the Morphological Characteristics of Secondary Fiber Obtained from Wet-Strength Paper During Gentle Refining of the Recycled Pulp. Part 2. Fines Characteristics. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 4, pp. 169–179. (In Russ.). https://doi.org/10.37482/0536-1036-2023-4-169-179

Boron doped diamond electrode for efficient persulfate generation: The modulation of boron doping level on interfacial electron transfer

The inefficient Faradaic efficiency of electro-synthesis of sodium persulfate (Na2S2O8) hinders its industrial application. In this work, modulated high-performance boron-doped-diamond (BDD) electrodes were used to Na2S2O8 electro-synthesis. The effect of boron doping level of BDD electrode on Na2S2O8 generation was studied for the first time. Based on electro-synthesis results, BDD (0.05% B) electrode produced more Na2S2O8 (41.85 mM at 120 min) with the Faradaic efficiency of 90% that is the highest value reported in the literatures. Na2S2O8 was generated by ·OH mediated indirect oxidation, and the BDD (0.05% B) electrode produced more ·OH. Furthermore, the less C-O functional groups on the BDD (0.05% B) electrode surface inhibited the interfacial electron transfer of H2O to O2, and therefore promoted ·OH formation. These findings highlight the relationship between boron doping level, surface functional groups, interfacial electron transfer process and Na2S2O8 generation, providing a theoretical guidance for efficient Na2S2O8 electro-synthesis.

High-efficiency leaching of Li and Ni from spent lithium-ion batteries based on sodium persulfate

Herein, the preferential leaching of Li and Ni from spent lithium-ion batteries was put forward for the first time. Firstly, the stable structure of cathode material was destroyed by reduction roasting, and then Li and Ni in roasted product were leached in sodium persulfate solution. Through adjusting the redox potential and pH of the solution, Li and Ni could exist in the solution in the form of Li+ and Ni2+, while Co and Mn remained in the residue mainly in the form of Co3O4 and MnO2. The leaching efficiencies of Li and Ni were 95.07% and 96.02% under the optimized conditions, respectively. Kinetic analysis showed that the leaching process was controlled by surface chemical reaction. In addition, XPS, XRD, thermodynamic analysis, and SEM-EDS were used to explore the mechanism. This method could effectively simplify the recovery and separation process, providing a new thought for the utilization of spent lithium-ion batteries.

Combining electrochemistry and ultraviolet radiation for the degradation of per- and poly-fluoroalkyl substances in contaminated groundwater and wastewater

Electrochemical and ultraviolet-based methods are advanced oxidation processes emerging as viable water and wastewater treatment options. In this study, a combination of these two methods (EO-UV) using boron-doped diamond (BDD) electrodes and ultraviolet radiation at both 185 and 254 nm was assessed for the degradation of poly-fluoroalkyl substances (PFAS). Sodium persulfate (Na2S2O8) and sodium sulfate (Na2SO4) were used as electrolytes. The method was investigated on model solutions containing perfluorooctanoic acid (PFOA) and perfluorosulfonic acid (PFOS). The method's effectiveness was assessed by comparing PFAS removal efficiencies and energy demands associated with the use of separate and combined treatments. The results showed that the highest removal of PFOA and PFOS was 96 % and 85 % respectively, which was achieved using EO-UV and persulfate electrolytes. Average removal efficiencies were 1.5–2 times higher in EO-UV than in EO and 4–6 times higher than in UV treatment. The degradation of PFAS under EO-UV and persulfate applied to PFAS-contaminated groundwater and wastewater reached 94 % PFOA and 88 % PFOS in groundwater and 51 % and 63 % in wastewater. The removal of the sum of eleven PFAS was 86 % and 66 % in groundwater and wastewater, respectively. The combination of EO, UV and persulfate was the most effective option for PFAS treatment at lower energy consumption.

Simultaneous remediation of arsenic and organic chemicals contaminated soil and groundwater using chemical oxidation and precipitation/stabilization: a case study.

After the departure of industrial facilities, reuse of the land in developed cities in China is problematic, due to the land contamination issues. The rapid remediation of sites with complex contamination is crucial and urgently needed. Herein, the case of on-site remediation of arsenic (As) in soil, as well as benzo(a)pyrene, total petroleum hydrocarbons, and As in groundwater was reported. For contaminated soil, the oxidant and deactivator (consisting of 20% sodium persulfate, 40% ferrous sulfate (FeSO4), and 40% portland cement) were applied to oxidize and immobilize As. As a result, the total amount and lixivium concentration of As were constrained under 20 mg/kg and 0.01 mg/L, respectively. Meanwhile, for contaminated groundwater, As and organic contaminants were treated by FeSO4/ozone and FeSO4/hydrogen peroxide with mass ratios of 1:5 and 1:8, respectively. The continuous monitoring of contaminants in 22 monitoring wells shown that all contaminants in groundwater were treated to meet the standards. In addition, the risk of secondary pollution and operation cost was effectively reduced by proper disposal and resourceful utilization. The findings indicated that the method of oxidation and precipitation/stabilization is technically, environmentally, and economically feasible for the remediation of contaminated sites with similar complex pollutants.

Enhanced catalytic levofloxacin degradation via persulfate activation over amorphous potassium ferricyanide@ZIF‐67 nanocages

AbstractA facile method was used to synthesize amorphous potassium ferricyanide (PF)@ZIF‐67 nanocages, a novel metal–organic framework derivative. The structure, composition and morphology of PF@ZIF‐67 were analysed by scanning electron microscopy, transmission electron microscope, X‐ray diffraction and X‐ray photoelectron spectroscopy. The results show that PF@ZIF‐67 nanoparticles were successfully prepared and its nanostructure has high crystallinity. The prepared materials were employed as heterogeneous persulfate catalysts for the degradation of levofloxacin (LEV). The effects of some key parameters including sodium persulfate (PS) dosage, PF@ZIF‐67, initial solution pH and reaction time on LEV degradation were investigated. PF@ZIF‐67 showed higher catalytic capacity for LEV degradation compared to ZIF‐67, implying the iron‐cobalt synergy in the material. Under the optimized conditions of 8.4‐mM PS, 0.5 g/L PF@ZIF‐67 at an initial solution pH of 7.2, 85.8% of LEV could be removed within 240 min. The quenching experiments suggest that sulfate radicals were the predominant reactive species.

Natural coal gangue activated persulfate for tetracycline hydrochloride degradation: Mechanisms, theoretical calculations, and comparative study

The development of catalysts with low-cost and high-efficiency for advanced oxidation process is the key issue to remove organic pollutants. In this work, natural coal gangue (CG) was used to activate potassium monopersulfate (PMS) for the removal of tetracycline hydrochloride (TC). For comparison, sodium persulfate (PS), potassium persulfate (PDS), and hydrogen peroxide (H2O2) were also activated by CG to remove TC. The active species in the TC degradation processes in PMS/CG, PS/CG, PDS/CG, and H2O2/CG systems were investigated by capture experiments and electron spin resonance (ESR) tests. DFT calculation indicated that PMS was more easily adsorbed by CG in comparison with PS, PDS, and H2O2. In addition, Fukui function was adopted to determine how electrophilic, nucleophilic and free-radical attacks occurred on sites of TC molecules in detail. Mechanism investigation showed that the surface-bonded and structural hydroxyl groups of natural CG were favorable for the adsorption of PMS molecules onto the CG surface and thus facilitated the generation of active species, which were crucial in the TC degradation process. This paper sheds new light for natural minerals or solid wastes to participate in advanced oxidation process (AOPs) for wastewater treatment.

Activation of persulfate by iron‐loaded soybean straw biochar for efficient degradation of dye contaminants: Synthesis, performance, and mechanism

AbstractBiochar loaded with metal ions has been widely used to activate persulfate to degrade organic pollutants. However, the preparation conditions of catalysts are always controversial. In this study, the co‐heating conditions of soybean straw with high carbon and low nitrogen and nano‐iron oxide were systematically discussed by response surface method, and an efficient catalyst (Fe@BC) was obtained. Fe@BC can effectively activate sodium persulfate (PS) and degrade three synthetic azo dyes (Methyl orange (MO), Amino black 10B (AB10B), and Orange II) and rhodamine B (RhB). Under the optimum conditions, the removal rate of total organic carbon of these four dyes reached 41.1%–89.8% and the final degradation rate could reach 100%. The physicochemical properties of Fe@BC were studied by SEM, BET, XRD, XPS and TGA. The results revealed that the specific surface area of Fe@BC was 195.6m2/g. Further, reducing iron oxide by C generated C0.09Fe1.91 and zero‐valent iron. Free radical scavenging experiments and electron paramagnetic resonance (EPR) measurements showed that the main reactive oxide species (ROS) in the Fe@BC/PS system were hydroxyl radicals (•OH) and singlet oxygen (1O2). Finally, Several Fe@BC modification systems were explored, the optimum pH of Fe@BC/PS system was analyzed, and the effects of Fe@BC and PS dosage on degradation performance were also studied. This study provides a scientific basis for the production of efficient catalysts and biochar energy, and an effective treatment scheme for printing and dyeing wastewater.

Sonochemical degradation of the artificial sweetener acesulfame in aqueous medium and identification of transformation products

The sonochemical degradation of acesulfame (ACE), a widely used artificial sweetener, was investigated. The impact of power density (40 and 71 W/L), initial ACE concentration (1.5–30.6 μΜ), and initial solution pH (3–9) for the elimination of the target pollutant from water was studied. It was found that nearly complete degradation of ACE was achieved within 120 min of treatment under conditions suitable for high production of free radicals. Degradation follows a pseudo-first order kinetic model. Coupling sonochemical degradation at optimal conditions with sodium persulfate (0.2–1.0 mM) enhanced the rate of ACE oxidation by six times. The influence of water complexity was also examined; the natural occurrence of humic acid in the water matrix reduced the degradation rate, despite the fact that at least 42 % of ACE removal was achieved. Finally, LC-QToF-MS was used to evaluate the generated transformation products (TPs). Using HRMS suspect and non-target screening, seven ACE TPs were identified, and their time-trend formation profiles showed a rising trend throughout the experiment. According to the ECOSAR model, most of the identified transformation products exhibited lower toxicity than acesulfame, with one notable exception that was classified as harmful due to its acute toxicity on fish and green algae.

Light-activated extracellular matrix microcarriers with engineered MSCs loading for autoimmune psoriasis treatment

The stem-cell-therapy supported by hydrogel microcarriers has shown potentials in the regulation of autoimmune diseases. Trends in this field focus on enhancing the viability and the delivery controllability of stem cells. Herein, we proposed novel fish extracellular matrix (ECM) microcarriers loaded with mesenchymal stem cells (MSCs) that secrete programmed cell death-ligand 1 (PD-L1) for autoimmune disease treatment. We developed an optimized acellular method to extract the fish skin ECM, followed by mixing it with ruthenium (Ru)/sodium persulfate (SPS) to generate light-activated ECM bio-ink. By introducing this bio-ink into a droplet microfluidic device, porous ECM microcarriers could be generated after in-situ photocrosslinking. With the decoration of polydopamine, MSCs with enhanced PD-L1 expression by lentivirus transfection can adhere well to these ECM microcarriers, serving as ideal candidate for stem-cell-therapy. We have demonstrated that the engineered MSCs delivered through the ECM microcarriers have a higher survival rate compared with direct injection. Besides, these MSCs-loaded microcarriers can effectively inhibit the epidermis thickening and lower the PASI score in an in vivo psoriasis model. Therefore, the proposed engineered MSCs-loaded ECM microcarriers are anticipated to pave the way for promising clinical treatments of autoimmune psoriasis diseases.

Effects of various persulfate oxidation pretreatments on enzymatic saccharification efficiency of sugarcane bagasse biomass and the related mechanism

This study explored the impact of different persulfate pretreatments on the substrate characteristics and enzymatic sugar yield of sugarcane bagasse (SCB) and the related mechanisms. We analyzed the biomass composition, physicochemical properties of SCB, enzymatic saccharification efficiency, pure commercial cellulose and lignin degradation dynamics, and ·OH and SO4∙ − generation properties under different persulfate pretreatments. The results revealed that potassium peroxymonosulfate (2KHSO5·KHSO4·K2SO4, PPMS) pretreatment had a significant effect on SCB. Under the optimal pretreatment conditions, SCB pretreated with PPMS showed a reducing sugar yield of 67.98%, a sugar conversion rate of 90.29%, and a lignin removal rate of 87.49%, which were about 2–3 folds those under pretreatment with peroxydisulfate (PDS) including sodium persulfate (Na2S2O8, SPS) and ammonium persulfate ((NH4)2S2O8, APS). PPMS had higher selectivity for lignin degradation and stronger free radical generation ability than PDS, which may be the main contributor to its superior pretreatment performance.

3D bioprinting of tyramine modified hydrogels under visible light for osteochondral interface

Recent advancements in tissue engineering have demonstrated a great potential for the fabrication of three-dimensional (3D) tissue structures such as cartilage and bone. However, achieving structural integrity between different tissues and fabricating tissue interfaces are still great challenges. In this study, an in situ crosslinked hybrid, multi-material 3D bioprinting approach was used for the fabrication of hydrogel structures based on an aspiration-extrusion microcapillary method. Different cell-laden hydrogels were aspirated in the same microcapillary glass and deposited in the desired geometrical and volumetric arrangement directly from a computer model. Alginate and carboxymethyl cellulose were modified with tyramine to enhance cell bioactivity and mechanical properties of human bone marrow mesenchymal stem cells-laden bioinks. Hydrogels were prepared for extrusion by gelling in microcapillary glass utilizing an in situ crosslink approach with ruthenium (Ru) and sodium persulfate photo-initiating mechanisms under visible light. The developed bioinks were then bioprinted in precise gradient composition for cartilage-bone tissue interface using microcapillary bioprinting technique. The biofabricated constructs were co-cultured in chondrogenic/osteogenic culture media for three weeks. After cell viability and morphology evaluations of the bioprinted structures, biochemical and histological analyses, and a gene expression analysis for the bioprinted structure were carried out. Analysis of cartilage and bone formation based on cell alignment and histological evaluation indicated that mechanical cues in conjunction with chemical cues successfully induced MSC differentiation into chondrogenic and osteogenic tissues with a controlled interface.

The efficiency of Fenton, Fenton/MW and UV/oxidant processes in the treatment of a mixture of higher concentrations of azo dyes

The concentration of dyes in the degradation process, as found in the literature, higher than 10 – 30 ppm is rarely found in the literature. The present study attempts to establish the degradation efficiency of a mixture of two azo dyes, Acid Blue 29 and Ponceau Xylidine at higher concentrations by Fenton, Fenton-type, photolysis and microwave assisted Fenton processes, employing hydrogen peroxide (HP) and sodium persulphate (SPS) as oxidants. It was observed that mixing of dyes enhances decolorisation and retards chemical oxygen demand (COD) and total organic carbon (TOC) removal in Fenton process. Nevertheless, COD removal efficiency (CODeff) was higher at pH 3 than at pH 5.9, the respective values being 72.8 and 61.2% in 300 min. Although, the COD removal in Fe2+/HP system was faster in the early stages than in UV/HP system, the later shows higher CODeff than the former (96.6 and 72.8%, respectively, in 300 min). This result is in good agreement with the consumption pattern of HP in both systems. Although contradicting in nature, our finding, that the inhibition of degradation by persulphate, is remarkable. Although, microwave (MW) irradiation accelerated Fenton process, the overall COD removal was not increased. The effect of inorganic ions and hydroxylamine on the Fenton process has been reported in this study. Toxicity assessment by both colony forming units (CFUs) and light loss method shows that the detoxification efficiency of different processes are in the order UV/HP>Fe2+ /HP.

Persulfate-Induced Three Coordinate Nitrogen (N3C) Vacancies in Defective Carbon Nitride for Enhanced Photocatalytic H2O2 Evolution

In-situ photocatalytic H 2 O 2 production has been receiving increasing attention in recent years for sustainable H 2 O 2 synthesis. Graphitic carbon nitride (g-C 3 N 4 ) is regarded as one of the most promising semiconductor photocatalysts for H 2 O 2 evolution. Introducing N defects in g-C 3 N 4 has been proved to be an effective strategy to enhance photocatalytic activity. However, the photocatalytic mechanism of the N vacancies is ambiguous and different types of N vacancies in g-C 3 N 4 may exhibit different effects on photocatalytic activity. Herein, we develop a facile sodium persulfate eutectic polymerization method to prepare the g-C 3 N 4 with abundant three coordinate nitrogen (N3 C ) vacancies. This type of nitrogen vacancy has not been studied in g-C 3 N 4 for photocatalytic H 2 O 2 production. Our results showed that the introduction of N3 C vacancies in the g-C 3 N 4 successfully broadened the light absorption range, inhibited the photoexcited charge recombination with enhanced O 2 adsorption to promote oxygen activation. The photocatalytic H 2 O 2 evolution from the N3 C -rich g-C 3 N 4 is 4.5 times higher than that of the pristine g-C 3 N 4 . This study demonstrates a novel strategy to introduce N3 C vacancies in g-C 3 N 4 , which offers a new method to develop active catalysts for photocatalytic H 2 O 2 evolution.