Acid-alkali Treatment Research Articles

COMPARISON OF TWO METHOD FOR ISOLATION OF FIBRILLATED CELLULOSE FROM LIGNOCELLULOSIC BIOMASS

Fibrillated cellulose from distillery refuse based on maize starch was prepared by two different procedures. The effect of sonification was evaluated atacid-alkali extractionas well as the type of used acid. The results from the alkali-acid procedure were compared with these obtained by method of steam explosion at different temperatures. The acid-alkali method brings a better result regarding degradation of hemicellulose and lignin as well as cellulose. Lignin/hemicellulose were only released from lignocellulose network using steam explosion at 120-180°C. At higher temperature, the results were comparable with those obtained by acid-alkali method. Similarly pore size distribution of filter paper decreased more significantly when fibrillated cellulose from acid-alkali treatment was applied. After steam explosion, higher extend of longer still fibres remains.

Characterization of chitosan derived from mushroom sources: Physicochemical, morphological, thermal analysis

This research explores chitosan from mushrooms actively cultivated in Malaysia, focusing on its physicochemical, morphological, and thermal properties. The extraction method involves four stages of acid-alkali treatment (HCl and NaOH) with constant conditions across all samples. Chitosan from seven mushroom species and commercially available chitosan (labelled A1 to A8) are compared due to scarce data on mushroom chitosan. Chemical composition results reveal ash (0.65%–3.33%), moisture (4.29%–6.94%), degree of deacetylation (DD%) from 19.15% to 81.94%, and functional group peaks including hydroxyl, amine and carbonyl group. Physical properties present fat binding capacity (FBC) from 354.26% to 649.91%, water binding capacity (WBC) from 124.83% to 522.42%, solubility (50.02%–100.00%), intrinsic viscosity (ƞ) from 1.79 dL/g to 5.26 dL/g, average molecular weight (Mv) from 54.26 kDa to 215.26 kDa, and crystallinity index (CrI) from 49.07% to 75.67%. Structural analysis demonstrates rougher surfaces and irregular shapes for the majority of samples. The thermal analysis includes mass loss (68.07%–73.64%), decomposition temperature (220.98 °C–354.29 °C), and glass transition temperature (Tg) from 201.76 °C to 350.94 °C. Overall, mushroom chitosan could serve as an alternative source due to its superior FBC compared to animal-derived chitosan and better thermal stability than commercial chitosan, highlighting its versatility for various applications.

Activating Adsorption Sites of Waste Crayfish Shells via Chemical Decalcification for Efficient Capturing of Nanoplastics.

The property of being stubborn and degradation resistant makes nanoplastic (NP) pollution a long-standing remaining challenge. Here, we apply a designed top-down strategy to leverage the natural hierarchical structure of waste crayfish shells with exposed functional groups for efficient NP capture. The crayfish shell-based organic skeleton with improved flexibility, strength (14.37 to 60.13 MPa), and toughness (24.61 to 278.98 MJ m-3) was prepared by purposefully removing the inorganic components of crayfish shells through a simple two-step acid-alkali treatment. Due to the activated functional groups (e.g., -NH2, -CONH-, and -OH) and ordered architectures with macropores and nanofibers, this porous crayfish shell exhibited effective removal capability of NPs (72.92 mg g-1) by physical interception and hydrogen bond/electrostatic interactions. Moreover, the sustainability and stability of this porous crayfish shell were demonstrated by the maintained high-capture performance after five cycles. Finally, we provided a postprocessing approach that could convert both porous crayfish shell and NPs into a tough flat sheet. Thus, our feasible top-down engineering strategy combined with promising posttreatment is a powerful contender for a recycling approach with broad application scenarios and clear economic advantages for simultaneously addressing both waste biomass and NP pollutants.

Biowaste Valorization of Palm Tree Phoenix dactylifera L. for Nanocellulose Production.

The desire to reduce reliance on oil resources arises from the concerns about carbon footprint and nonrenewability. Conversely, the global presence of over 100 million palm trees poses a significant challenge due to the substantial amount of biowaste generated annually. Additionally, the use of nanocellulose (NC) as a cost-effective material is steadily gaining recognition for its growing adaptability over time. The main goal of this study is to biosynthesized NC from Iraqi date palm Phoenix dactylifera leaves waste with low-concentration acid-alkali treatment. The date palm leaves waste yields 20 g of NC from 100 g of leaves before acid hydrolysis treatment. The chemical components of biosynthesized NC were 47.90%, 26.78%, and 24.67% for α-cellulose, hemicellulose, and lignin, respectively. In order to study their properties, NC from raw date palm leaves was studied by microscopic techniques such as scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, and atomic force microscope (AFM). SEM results revealed rod-like structured NC as well as combined long-fine fibrous structures rather than compacted bundles with sizes ranging between 31 and 74 nm. With EDX, all spectra exhibit the peaks of carbon and oxygen as the main elements with 63.8% and 10.44%, respectively, in their compositions, which relate to the typical composition of cellulose. The 3D image of AFM NC with a tapping mode presented a highly uniform distribution of NC with a size of ∼15 nm. The statistical roughness analysis shows that the obtained roughness average is 7.20 nm with the root-mean-square roughness value of 21.56 nm, which corresponded relatively with the micrographs of SEM. The results of this study demonstrate the promise of using date palm waste as raw material to produce NC as green nanocomposite from biodegradable nanomaterials for water purification and sustained drug delivery for biomedical applications. In this regard and because of the insufficient reports about the extraction of NC from palm tree leaves waste, the objective of this study was designed to fabricate NC biologically from fibers sourced from the waste of Iraqi date palm P. dactylifera leaves that left in agricultural lands or burned, which can be an ecological and health problem as a bionanocomposites in the medical and industrial field and as alternative resources of wood materials.

Effect of post-processing and variation of the building angle of Ti-6Al-4 V disks obtained by selective laser melting: A comparison of physical, chemical and mechanical properties to machined disks

Additive Manufacturing (AM) is driving the development of dental implants with freedom of design, material savings, and predictable properties. The modification of a single parameter, and post-processing treatments affects the final macro and microstructure. The aim was to evaluate the effect of changing the building angle, using the Selective Laser Melting (SLM) technique, on the physical, chemical, and mechanical properties and to compare them with sanded manufacturing surfaces and machined surfaces, with and without chemical surface treatment. There were 8 groups of Ti-6Al-4 V discs (Ø 10 mm×2 mm), classified as machined (M), machined with acid-alkali treatment (TM), SLM 0° (AM0), SLM 0° with sanding (SAM0), SLM 45° (AM45), SLM 45° with sanding (SAM45), SLM 90° (AM90), and SLM 90° with sanding (SAM90). The tests used were Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), roughness, wettability, surface free energy, X-ray diffraction (XRD), and Vickers hardness. The normality of the data was checked using the Shapiro-Wilk test followed by Kruskal-Wallis and ANOVA, with Dunn and Tukey post-tests, with a significance level of 5%. SEM revealed angle dependence in the number of unmelted powder particles and topographical heterogeneity, and EDS reported the elemental composition of the base alloy. AM90 showed the highest wettability among the manufactured groups, and the chemical surface treatment increased the wettability of the machined sample (p<0.001). In the roughness analysis, the higher the building angle, the higher the surface roughness . Sanding provided homogeneity in roughness, wettability, surface free energy, and microhardness. It was concluded that the production routes, change in angle, sanding and surface treatment affect the macro and microstructure of titanium surfaces. Changing the building angle influenced all of the topographical characteristics of the material, a parameter that can be changed and improved that is important for determining properties.

Preparation, characterization, and evaluation of ketoconazole-loaded pineapple cellulose green nanofiber gel

The present study involves the isolation of cellulose nanofibers from pineapple crown waste by a combined alkali-acid treatment method. The extracted pineapple nanofibers were characterized by Fourier-transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, nuclear magnetic resonance, high-resolution transmission electron microscopy, and dynamic light scattering. The extracted pineapple nanofibers were then incorporated in Carbopol 934P containing ketoconazole to prepare a ketoconazole-loaded pineapple nanofibrous gel. The prepared gel formulation was evaluated for viscosity, spreadability, extrudibility, pH, drug content, and texture profile analysis. The anticipated gel formulation was further evaluated by in vitro drug release (98.57 ± 0.58 %), ex vivo drug permeation, cytotoxicity, and histopathological studies. The permeation of the drug through skin determined by the ex-vivo diffusion study was found to be 38.27 % with a flux rate of 4.06 ± 0.26 μg/cm2/h. Further, the cytotoxicity study of pineapple nanofiber and ketoconazole-loaded nanofiber gel displayed no cytotoxic on healthy vero cells in the concentration range from 10 to 80 μg/ml. The histopathological analysis exhibited no signs of distress and inflammation. In conclusion, ketoconazole-loaded pineapple nanofiber gel could be considered as a promising delivery system for topical applications.

Unveiling Carrier Relaxation Mechanism in Protonated/Deprotonated Carbon Dots and Their Solvent Effects via Ultrafast Spectroscopy.

The intricate nature of the surface structure of carbon dots (CDs) hinders a comprehensive understanding of their emission behavior. In this study, we employ two types of CDs created through acid-alkali treatments, one with surface protonation and the other with surface deprotonation, with the objective of investigating the impact of these surface modifications on carrier behavior using ultrafast spectroscopy techniques. TEM, XRD, FTIR and Raman spectra demonstrate the CDs' structure, featuring graphitic core and abundant surface functional groups. XPS confirms the successful surface modifications of CDs via protonation and deprotonation. Ultrafast transient absorption (TA) spectroscopy reveals that deprotonation modification may decelerate the relaxation process, thereby increasing the visible PL quantum yields (PLQY). Conversely, protonation may accelerate the relaxation process due to the induced low-energy absorption band, resulting in self-absorption and reduced PLQY. Furthermore, TA analysis of CDs in mixed solvents with different proportions of ethanol shows the beneficial effect of ethanol in decelerating the relaxation process, leading to an increased PLQY of 33.7 % for deprotonated CDs and 22.1 % for protonated CDs. This study illuminates the intricate relationship between surface deprotonation/protonation modifications and carrier behavior in CDs, offering a potential avenue for the design of high-brightness CDs for diverse applications.

Preparation and characterization of highly crystalline hydroxyapatite (HAp) from the scales of an anadromous fish (Tenualosa ilisha): a comparative study with the freshwater fish scale (Labeo rohita) derived HAp.

Waste generation from fish processing sectors has become a significant environmental concern. This issue is exacerbated in countries with high aquaculture production and inefficient fish scale (FS) utilization. This study prepared and compared highly crystalline hydroxyapatite (HAp) from the FS of an anadromous fish, Tenualosa ilisha (I-HAp), and a freshwater fish, Labeo rohita (R-HAp). Acid-alkali treatment followed by high-temperature calcination was employed for HAp synthesis. XRD analysis indicated a monoclinic crystal structure for I-HAp and a hexagonal structure for R-HAp, with both containing β-TCP as a secondary phase. Rietveld refinement quantified β-TCP at 8% for I-HAp and 7.2% for R-HAp. Crystallite size of the samples was estimated by various methods (Scherrer's method, Scherrer equation average method, linear straight-line method, straight line passing the origin method, Monshi-Scherrer method, Halder-Wagner method, Williamson-Hall method, and size-strain plot method), consistently indicating microcrystalline HAp. FESEM and TEM analyses revealed larger particle sizes for I-HAp, confirmed by DLS measurements. Surface elemental analysis by XPS confirmed the presence of Na and Mg as impurities along with the elements of the HAp structure. FTIR and Raman spectroscopy identified expected functional groups, while EDX determined elemental composition. Both HAp samples exhibited bioactivity through apatite layer formation in simulated body fluid. Furthermore, the combined results of the cell viability and hemocompatibility studies indicate the biocompatibility of the prepared samples.

Low-cost and eco-friendly fluidized bed hydrogen reduction assisted electroless plating to synthesize Ni-coated graphite

Electroless plating is the main method for preparing metal-coated composite powders, such as Ni-coated graphite powders with wide applications in electromagnetic shielding materials, sealing coating, and electrocatalysis. However, the issues of uniform and dense coating during synthesis are hindering its practical implementation. Incorporating noble metals, such as Pd, to activate powders is a typical technique to prepare an electroless Ni coating. However, noble metal utilization is hindered by issues such as high costs and substantial wastewater. Herein, a novel low-cost and eco-friendly activation method based on fluidized bed hydrogen reduction is designed to prepare densely coated Ni@irregular graphite particles (Ni@IGP) using a low Ni content. This method can be used to construct a uniform and dense Ni coating for composite powders without acid alkali treatment and use of precious metals during the overall manufacturing process. Results demonstrated that the Ni@IGP particle obtained through this approach have good electrical conductivity and ferromagnetic properties. In addition, the uniformity and integrity of the Ni plating were adjusted, and the dense coating of graphite at a low Ni content of 35 wt% was effectively achieved. This new activation method sheds light on the field of electroless Ni plating on powders.

PI nanofiber membranes with pH-responsive wettability fabricated through solution blow spinning for efficient on-demand oil-water separation

Nanofiber membranes (NFMs) are widely used in oil-water separation area due to their unique structure and properties. However, achieving efficient and on-demand separation of oil-water mixtures using NFMs remains a challenge. Herein, we prepared polyimide nanofiber membranes (PI-NFMs) with fluffy structures through solution blow spinning (SBS), and the average diameter of the PI nanofibers was 506.1 ± 75.6 nm. The PI-NFMs exhibited excellent pH responsiveness, demonstrating the ability to swiftly convert their wetting properties between highly hydrophobic and superhydrophilic through a simple acid-alkali treatment. Additionally, the conversion between oil removing model and water removing model according to the type of oil-water mixture was realized. The performance of the membranes in separating oil and water was evaluated using five different densities of oil-water mixtures. Only driven by gravity, the membrane exhibits good separation efficiency and extremely high permeate fluxes with the water and oil fluxes to 37,641.84 and 71,083.16 L·m−2·h−1, respectively, which also shows decent reusability. This work presents a promising solution for the intelligent, efficient, and controllable treatment of industrial oil effluents and oil spills.

Wood biochar enhances methanogenesis in the anaerobic digestion of chicken manure under ammonia inhibition conditions

The process of breaking down chicken manure through anaerobic digestion is an effective waste management technology. However, chicken manure can be a challenging feedstock, causing ammonia stress and digester instability. This study examined the impacts of adding wood biochar and acid-alkali-treated wood biochar to anaerobically digest chicken manure under conditions of ammonia inhibition. The results highlighted that only the addition of 5 % acid-alkali-treated wood biochar by volume can achieve cumulative methane production close to the typical methane potential range of chicken manure. The treated wood biochar also exhibited highest total ammonia nitrogen removal compared to the Control treatment. Scanning Electron Microscope revealed growing interactions between biochar and methanogens over time. Real-time polymerase chain reaction showed that treated wood biochar produced the highest number of bacterial biomass. In addition, 16S amplicon-based sequencing identified a more robust archaeal community from treated biochar addition. Overall, the acid-alkali treatment of biochar represents an effective method of modifying biochar to improve its performance in anaerobic digestion.

N and P removal from wastewater using rice husk ash-derived silica-based Fe-ZSM-5 zeolite

N and P are essential elements for crop-based food production. With increasing ammonia and phosphate fertilizers used in agricultural land, water pollution in nearby waterbodies is also increasing from respective runoffs. In this study, ZSM-5 (Zeolite Socony Mobil-5), zeolite having Si/Al ratio of 22, with and without iron-incorporated was hydrothermally synthesized using extracted silica by alkali-acid treatment from rice husk ash. The synthesized zeolites were characterized using XRD, SEM, EDS, N2-sorption, XPS and STEM. Batchwise sorption studies of NH4+-N and PO43--P from synthetic solutions were carried out. Enhanced N and P adsorption capacities were found for Fe-ZSM-5 zeolites. Notably, a 3-fold better P-sorption ability was found for Fe-ZSM-5 compared to Na-ZSM-5. A regeneration study using 0.5 M NaCl solution was carried out and Fe-ZSM-5 zeolite retains 97% and 88% of N and P-removal ability. The simple synthesis step, utilization of waste rice husk, and excellent N and P removal capabilities suggest that the synthesized Fe-ZSM-5 zeolite is an excellent choice for sustainable adsorbent for water pollution control.

Coconut coir-derived nanocellulose as an efficient adsorbent for removal of cationic dye safranin-O: a detailed mechanistic adsorption study.

Coconut (Cocos nucifera) coir is an abundant agricultural waste prevalent worldwide. Utilization of this waste has been carried out in this study by obtaining nanocellulose (NC) fibres for wastewater remediation purposes. Nanocellulose was obtained from coconut coir using bleaching and acid-alkali treatments followed by ultrasonication and lyophilization. The structural, compositional, surface and thermal properties of the synthesized material were identified using transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption/desorption, differential thermal (DT) and derivative thermogravimetric (DTG) analyses. These analyses confirmed the synthesized NC with enhanced thermal stability and porosity which was further used for adsorption process. After synthesis, NC was used for the removal of cationic dye safranin-O from water under ambient conditions through batch adsorption studies. The batch adsorption studies revealed that at 10ppm of dye concentration, above 99% removal was achieved by 100mg dosage of NC within 4.5h at room temperature with qe (maximum adsorption capacity at equilibrium)value of around 83mgg-1. The corresponding adsorption process fitted well with Langmuir isotherm and pseudo-second order kinetics. Theprimary mode of adsorption from the thermodynamic studies was found to be chemisorption. The adsorption process was achieved through response surface methodology (RSM) study which revealed that at optimized conditions of temperature 35°C with a dose of 137.50mg and contact time of 180min, above 99% of dye (conc. 0.01mgmL-1) was removed. In addition, the adsorbent can be recycled up to six cycles without any significant loss of its adsorption capacity. The present comprehensive study revealed that a greener eco-friendly synthesis ofNC from waste material coconut coir was an effective nanoadsorbent for dye removal withhigh efficacy. This surely opens up opportunities to develop sustainable protocols for efficient environmental remediation.

Oxygen vacancy engineering on copper-manganese spinel surface for enhancing toluene catalytic combustion: A comparative study of acid treatment and alkali treatment

Copper-manganese spinel is a low-cost VOCs catalytic combustion catalyst with good performance. Oxygen vacancy has excellent properties for oxygen activation and VOCs dehydrogenation activation, which is beneficial for the catalytic combustion of VOCs. In this study, a large number of oxygen vacancies were introduced on the copper-manganese spinel surface by selective dissolution method (acid treatment and alkali treatment) for catalytic combustion of toluene. Furthermore, the effects of acid treatment and alkali treatment on the catalytic performance, oxygen vacancy amount, physical and chemical properties, and toluene catalytic combustion mechanism of copper-manganese spinel were studied. Both acid treatment and alkali treatment can produce large quantities of oxygen vacancies on the copper-manganese spinel surface. The generation of surface oxygen vacancies can greatly improve the catalytic combustion activity of copper-manganese spinel. At 240 °C, the combustion rate of toluene increased by 8.8 times for the acid-treated catalyst and 11.2 times for the alkali-treated catalyst. The numerous surface oxygen vacancies, Mn3+/Mn4+ at the ratio of 1.11 and appropriate acidity result in the alkali-treated catalyst exhibiting excellent catalytic activity and stability for toluene combustion. This strategy provides a new method to further improve catalytic combustion activity of copper-manganese spinel and a reference for the development of the surface oxygen vacancy engineering of transition metal oxides.

Palynozonation of Akukwa-2 Well, Anambra Basin: Implications for Age and Paleoenvironment

Palynological examination of twenty (20) ditch shale samples from sedimentary succession penetrated by Akukwa-2 Well at depth interval of 3,296 - 3,850 m was undertaken to investigate the occurrence of Palynomorph in the sediments of Anambra Basin with a view to determining the age of the sediments and reconstruct the depositional paleoenvironment. Standard Palynological procedure was followed and the samples were processed using the conventional acid maceration, alkali treatment and staining methods. The oxidized residues were sieved with 5micron nylon sieves using digital Sonifier 450 machine and mounted on glass slides with Norland adhesive gel. Laborlux 12 (Ernst Leitz) transmitting light microscope was used for identification and counting or the palynomorphs. The palynological analysis was done using the population and species of pollen grains, spores and dinoflagelate. The analyzed palynological slides yielded forty nine (49) palynomorphs species identify in the ditch samples, forty (40) were Miospores (pollen and spores) and nine were Dynocysts. However, some diagnostic forms that are stratigraphically useful are present and are used for the palynozonation. Delineation of the well section produced three main palynological zones based on stratigraphic distribution. Zone 1 characterized by the quantitative base appearance of Triorites Africaensis Assemblage indicating Marginal Marine paleoenvironment and of Turonian age; Zone 2, marked by Droseridites Senonicus assemblage also of Marginal Marine but of Coniacian age, Zone 3, marked by Milfordia spp. Acme Zone, purely Marine and of Campano- Maastrichtian age. The study further reveled that Palynomorph recovery in Akukwa-2 well was not that impressive both in terms of abundance and preservation. In most cases, the macerals present seems to indicate high geothermal effect suggesting that some of the kerogen might have been overcooked to imply inability&nbsp; to generate hydrocarbon or such generated hydrocarbon have turned into carbon.

Strong and biodegradable films from avocado peel fiber

Plastics are desirable as packaging materials due to their strong, flexible, and low-cost properties. However, their lack of biodegradability is environmentally detrimental. To this end, plant-based natural fiber is a viable option for creating plastic replacing and biodegradable materials. This study aimed to extract lignocellulosic fiber from avocado peel and make films. Acid hydrolysis and alkali treatment were used to obtain the fiber from avocado peel and ZnCl2 to solubilize it and make films by crosslinking the polymer chains through Ca2+ ions. The results reveal that increasing the Ca2+ ions amount significantly reduces moisture content, moisture absorption, water vapor permeability, water solubility, transparency, and elongation at the break of films but improves tensile strength. The films biodegrade within 30 days at the soil moisture content of 22% with a half-life of 3.19–4.63 days. Overall, extract from avocado peel fiber could aid in designing and developing plastic replacement and biodegradable packaging films.

Ultra/loose nano-filtration polyarylene ether sulfone membranes with reversibly tunable pore size enabled via amine oxide units

Developing a new generation of polymer membranes with switchable pores for multiple separation processes remains challenging due to the lack of materials with reversible and adjustable chemical structures. Herein, amine oxide units were introduced in the chains of poly (arylene ether sulfone) via oxidizing the tertiary amine (TA) in poly (arylene ether sulfone)/amide tertiary amine (PAES/ATA) copolymer, and then served as switches to tune the pores of the prepared membranes. The smart membranes could be reversibly tuned between loose nanofiltration mode with water permeance of 178 L m−2 h−1 bar−1 and dye (e.g., Rhodamine B) rejection of 95%, and ultrafiltration mode, with water permeance of 650 L m−2 h−1 bar−1 and dye rejection of 55%, by cyclic acid-alkali treatment. The mechanism of the switchable pore size was elucidated by dissipative particle dynamics (DPD) simulations, and the results were in good agreement with experimental results. This study provides a novel and facile route to fabricate functional membranes with reversibly tunable and highly efficient filtration performance, which could be applicable to multiple separations.

Sequential extraction of labile and recalcitrant fractions of soil organic matter: A case study focusing on antimony (Sb) in humic acids, fulvic acids and humin fractions of long-term aged contaminated soils

Soil organic matter (SOM) plays a key role in environmental chemistry of macro and micro nutrients as well as heavy metal (loids). In this research, a modified sequential extraction scheme was used to isolate labile and recalcitrant SOM from organic rich soils after 18 months of ageing with antimony. Humic substances were extracted with a mixture of 0.5 M sodium hydroxide +0.1 M sodium pyrophosphate solution from soils. Then soils deprived of humic substances were sequentially subjected to extraction with glycerol, citric acid, pre-treated with acid and extracted with boiling alkali mixture. The humic acids (HA) and fulvic acids (FA) of isolated SOM fractions were separated and HAs been characterized using FTIR, 1H NMR, and UV-VIS. Acid-alkali treatment of the most recalcitrant SOM fraction (A1-ROM) led to the extraction of sparingly soluble, highly aromatic compound with considerable amounts of N (44% of the extractable N), possibly due to the breakdown of bounds between aromatic rings and amine functional groups. Nevertheless, the highest content of C and TOC was associated with the glycerol extractable SOM. Substantial amounts of Fe and Al were extracted with glycerol, resulting in a dramatic rise of Sb in SOM extracts. The largest increase (60%) in Sb concentrations was observed after the removal of Fe with citric acid. The humic substances (HS) were responsible for 63% of extractable Sb, whereas even after exhaustive alkali extractions 22% of the total Sb remained in the residual humin fraction. Within the HS fraction, 95% of antimony was associated with the low molecular weight FAs. Antimony concentrations in organic fractions correlated significantly with TOC and N contents, possibly due to the role of amine functional groups in Sb complexation. The results of this research highlight the importance of Fe–Al-SOM bridging and humin fraction in sequestration of Sb in recalcitrant SOM pools.

Side grafting tertiary amine in polyaryl ether sulfone membranes for reversible-multiple separations

In this study, a new category of copolymer was designed by side grafting of tertiary amines (TA) on polyaryl ether sulfone. The synthesized copolymers PES/ATA displayed superior thermal properties with a glass transition temperature of 200–225 °C. These copolymers with favorable film-forming properties were used to fabricate ultrafiltration membranes via a phase inversion approach. Surprisingly, it was found that the filtration performance of these resultant membranes could be reversibly tuned between a facile acid oxidation (CH3COOH:H2SO4:H2O2 = 40:1:1) and alkali solution (solution of 20 wt% NaOH, immersed for 4–8 h) treatment. While the water flux of dye solution had a twofold reduction, the oxidized membranes showed distinctly enhancement of methylene blue rejection from 35% to 91.5% after oxidation treatment. Subsequently, alkali treatment of the oxidized membranes allowed their water flux to recover up to 89% as that of pristine membranes, and the methylene blue rejection can recover to almost the same as that of pristine membranes. This phenomenon was closely related to the introduced reactive TA units: the TA group in the polymeric membrane was converted into stimulus-responsive amine oxide (AO) unit, then its charge can be reversibly changed between the acid oxidation and alkali treatment, and that can be used to tune the electrostatic repulsion and further tuned the membrane pore size. In addition, compared with the polyarylene sulfone membrane, the mechanical properties of these membrane had almost no deterioration after several treatment cycle. This study supplies a novel and facile routine to fabricate functional membranes with reversible-tunable filtration properties.

Functionalized 3D-printed porous titanium scaffold induces in situ vascularized bone regeneration by orchestrating bone microenvironment

Titanium (Ti) and its alloys have been extensively explored for treating load-bearing bone defects. However, high-stress shielding, weak osteogenic activity, and insufficient vascularization remain key challenges for the long-term clinical outcomes of Ti-based implants. Herein, inspired by structural and functional cues of bone regeneration, a silicon-doped nano-hydroxyapatite (nSiHA)/titanium dioxide (TiO2) composite coating with a hierarchical micro/nano-network structure is constructed on the surface of a 3D-printed porous Ti scaffold via a combined strategy of acid-alkali (AA) treatment and electrochemical deposition technique, which not only endows the scaffold with excellent osteoinduction ability but can also effectively immobilize and release vascular endothelial growth factor (VEGF). The results of the in vitro cell experiments show that the functionalized Ti scaffold significantly promotes osteogenesis in bone marrow mesenchymal stem cells (BMSCs) and angiogenesis in human umbilical vein endothelial cells (HUVECs) by activating the extracellular signal-regulated protein kinase (ERK) and HIF-1α signaling pathways. After being implanted into a rat femoral condyle defect model, the functionalized Ti scaffold can induce in situ vascularized bone regeneration by orchestrating the two coupled processes of angiogenesis and osteogenesis. These findings indicate that the functionalized Ti scaffold has great potential in bone tissue regeneration and is a promising candidate for load-bearing bone defect repair.