Carboxyl Content Research Articles

Cellulose acetate-based smart gating membrane with pH/thermal response for flux control

Inspired by the stomatal opening and closing mechanism of plants, a cellulose acetate-based pH/thermal response smart gating membrane was designed through surface segregation mechanism by embedding stimulation-responsive poly(N- isopropylacrylaminde) (PNIPAM)/poly(acrylic acid) (PAAc) microgels in the membrane pore channels. The water flux of the optimized smart membrane (CAM1.5) is 0.420 L/m2·h at 20 ℃/pH= 11 and changes to 121 L/m2·h at 65 ℃/pH= 1 with the highest gating ratio of 174. Meanwhile, the membrane gating ratio can be further improved to 216 when citric acid is used as coagulation bath. The carboxyl group content in the PAAc side chain is decreased and the interaction between water and microgels is improved under acid environment, which promotes the surface segregation of microgel. In addition, there is significant increase in the wet strength owing to the covalent crosslinking of citric acid. A fluid control system was designed based on the tunable membrane pore structure. According to the change of temperature and pH of the reaction system, the membrane can be opened and closed independently to precisely control the flow of reactants. This smart membrane shows promising applications in micro/nano fluid valves and temperature/pH sensitive biochemical reactors.

Corn Silk Polysaccharides with Different Carboxyl Contents Reduce the Oxidative Damage of Renal Epithelial Cells by Inhibiting Endocytosis of Nano-calcium Oxalate Crystals.

Renal epithelial cell injury and cell-crystal interaction are closely related to kidney stone formation. This study aims to explore the inhibition of endocytosis of nano-sized calcium oxalate monohydrate (nano-COM) crystals and the cell protection of corn silk polysaccharides (CCSPs) with different carboxyl contents (3.92, 7.75, 12.90, and 16.38%). The nano-COM crystals protected or unprotected by CCSPs were co-cultured with human renal proximal tubular epithelial cells (HK-2), and then the changes in the endocytosis of nano-COM and cell biochemical indicators were detected. CCSPs could inhibit the endocytosis of nano-COM by HK-2 cells and reduce the accumulation of nano-COM in the cells. Under the protection of CCSPs, cell morphology is restored, intracellular superoxide dismutase levels are increased, lipid peroxidation product malondialdehyde release is decreased, and mitochondrial membrane potential and lysosomal integrity are increased. The release of Ca2+ ions in the cell, the level of cell autophagy, and the rate of cell apoptosis and necrosis are also reduced. CCSPs with higher carboxyl content have better cell protection abilities. CCSPs could inhibit the endocytosis of nano-COM crystals and reduce cell oxidative damage. CCSP3, with the highest carboxyl content, shows the best biological activity.

Improvement of amphipathic properties with molecular structure unfolding and activation of cottonseed protein as ultra stable and safe emulsifier by deamidation

By-product cottonseed proteins are excellent options for numerous applications due to their superior properties and lower cost. However, its complex folded structure and large molecular weight lead to lower reactivity and insufficient amphiphilicity. Cottonseed protein isolate (CPI) is less-soluble in water. Therefore, we improved the amphiphilicity of CPI with associated hydrolysis, molecular structure unfolding, and activation by alkaline-induced deamidation (at 24, 36, and 72 h) and produced three cottonseed protein hydrolysates CPH 24, 36, and 72. FTIR/UV-CD measurements confirmed the conformational changes and conversion of the structural content. Particle size decreased 2503.4–771.8 nm, while surface hydrophobicity (133.5–326.7), carboxyl content (1.13 × 10־3–2.09 × 10־3), and flexibility increased, signifying hydrolysis, unfolding, and amphiphilicity improvement. Longer deamidation (CPH 72) exhibited the best properties, its prepared emulsions were long-term stable under all the environmental stresses without visible phase separation after at least 40 days of storage except at pH 4. Compared to CPI, it had smaller droplets (939.3–264.9 nm) and larger absolute ζ-potential (−26.5 to −58.0 mV). From the in-vitro cytotoxicity test, deamidated CPI is extremely safer than commonly used synthetic surfactants. This research provides a new method for producing multifunctional emulsifiers from CPI, which could be utilized in the development of functional foods/non-foods.

Preparation of ammonium polyacrylate thickener via inverse emulsion polymerization: paste forming ability and rheological property

In this work, ammonium polyacrylate (NH4PAA) thickener was synthesized by the inverse emulsion polymerization method with acrylic acid and ammonia water as the aqueous monomer, C16–C31 n-alkanes (5# white oil) as the continuous phase, Span 80/Tween 80 as composite emulsifiers, and Tween 80 as the phase inversion agent, under the action of ammonium persulfate-sodium bisulfite initiation (APS-NaHSO3) and N, N’-methylene-bis-acrylamide (MBA) crosslinking. Gel permeation chromatography and Fourier transform infrared spectroscopy provided evidence for the synthesis of NH4PAA, with a molecular weight of 232,000. The carboxylic content and nitrogen content of the NH4PAA thickener are 23.5% and 3.37%, respectively. A response surface analysis and single factor experiment showed that the optimum synthesis conditions of the NH4PAA thickener were pH 6.5, monomer dosage 38.49 wt%, reaction temperature 45.5°C, initiation system APS and NaHSO3 (weight ratio 1:2) 0.34 wt%, MBA dosage 0.15%, and reaction time 3.2 h. The viscosity of the NH4PAA thickener is 15.7 Pa·s (under the condition of using a rotary rheometer for testing, the mass fraction of the thickener is 3 wt%), which exceeded the corresponding viscosity of diPh-2-CUM-O, SAMXG8 reported in the literature and commercial thickeners. Transmission electron microscopy showed that the NH4PAA thickener presented spherical morphology. Dynamic light scattering showed that the particle size was concentrated at 78.8 nm. A rheological test showed that the NH4PAA thickener was a pseudoplastic fluid with good thixotropy. The NH4PAA thickener gave nylon carpet good printability after jet printing. This work provides a theoretical basis for the development of high-quality thickeners for carpets in jet printing.

Analysis of causes for high hydration and low drainage rate of wheat straw chemi-thermo-mechanical pulp

The wheat straw chemi-mechanical pulp has the characteristics of high yield, good mechanical performance and low production cost. However, there are significant problems in the papermaking process by such as high pulp hydration, poor drainage, and large energy consumption during the paper drying-process. It was found that during the chemical mechanical pulping of wheat straw, due to the residual alkali and temperature, the hemicellulose in the pulp was continuously dissolved, some of it entered the water phase, and some of it migrated to the fiber surface. Which reflected in the raise in cation demand for anionic substances in the aqueous phase, the increase in carboxyl content on the surface of pulp fibers, and the aggravation in hydration degree. Further research found that the high valence metal ions can combine the carboxylate radical on the hemicellulose molecule in the aqueous phase with the carboxylate radical on the pulp surface to form a covalent bond, so that the hemicellulose entering the aqueous phase can be re-adsorbed to the fiber surface, thus further increasing the degree of pulp hydration. Carboxymethyl starch was used to simulate hemicellulose, and the hemicellulose re-adsorption phenomenon verification experiments were reproduced in a calcium ion environment. The above findings indicate that during the production of wheat straw chemi-mechanical pulp process, the hemicellulose dissolved and re-adsorption not only leads to the increase of pulp hydration, but also results in poor water filtration during paper formation. Therefore, this study can provide a theoretical basis for optimizing the production process of chemi-mechanical pulp of wheat straw and controlling the technology and method of pulp hydration.

Syntheses and dyeing properties of novel water‐soluble reactive sulphur black dyes

AbstractThe practical application of a sulphur black dye relies on its ability to dye cotton fibres with pure black colour and maintain the colour with high light fastness. Here, we report a synthesis method to prepare a novel water‐soluble reactive sulphur black dye. The approach involves the reduction of CI Sulphur Black 1 to its leuco form and subsequent reaction with a water‐soluble intermediate containing reactive groups synthesised from amino acid and cyanuric chloride. The optimal carboxyl and reactive group content of the water‐soluble reactive sulphur black dye is 141 mmol/100 g, and the water solubility can reach 92 g/L. The fixation of the reactive sulphur black dye on cotton reaches 89% in a pad dyeing process without using sodium sulphate. The reactive sulphur black dye can achieve a light fastness of grade 6‐7, a dry rub fastness of grade 4 and a wet rub fastness of grade 2, comparable or higher than the conventional CI Sulphur Black 1. The dyeing results showed that the novel water‐soluble reactive sulphur black dye has excellent performance and good application prospects.

Synthesis, metrological characterization, and dyeing properties of surface grafted viscose fabric using peroxydisulfate/ferrous II ions redox pair

Purpose The purpose of this study is to undertake surface graft copolymerization of viscose fabric via altering its fibrous properties by using acrylic acid (AA) as a carboxyl-containing monomer and peroxydisulfate (PDS) in presence of ferrous sulfate as a novel redox pair for initiating grafting. The latter process acted as an energy-saving process with respect to the reduction in polymerization temperature and maximizing the graft yield %, in addition to rendering the grafted viscose fabrics dye-able with cationic dye (crystal violet), which has frequently no direct affinity to fix on fabric. Design/methodology/approach To make graft copolymerization more efficient and economic, the optimum conditions for graft copolymerization were established. The graft yield % was determined as a function of initiator, catalyst and monomer concentrations and the material to liquor ratio, in addition to polymerization time and temperatures. Metrological characterizations via Fourier transform infrared spectroscopy and scanning electron microscopy of topographic morphological surface change have also been established in comparison with the ungrafted samples. Findings The maximum graft yield of 70.6% is obtained at the following optimum conditions: monomer (150 % based on the weight of fabric), PDS (50 m mole), ferrous sulfate (80 m mole) and sulfuric acid (30 m mole) at 40° C for 1.5 h using a liquor ratio of 30. Remarkably, grafting with AA enabled a multifold upsurge in color strength, with improvements in the fastness properties of cationically dyed grafted viscose fabric measured on the blue scale in comparison with untreated viscose fabric. Originality/value The novelty addressed here is undertaken with studying the effect of altering the extent of grafting of poly (AA)-viscose graft copolymers expressed as graft yield % in addition to carboxyl contents on cationic dyeing of viscose fabric for the first time in the literature. Moreover, rendering the viscose fabrics after grafting is dye-able with cationic dye with high brilliance of shades, which has regularly no direct affinity to fix on this type of fabrics.

Facile production of cellulose nanofibers from raw elephant grass by an aluminum chloride-enhanced acidic deep eutectic solvent

To develop a greener and more efficient method for producing cellulose nanofibers (CNFs) from raw plants, an AlCl3-enhanced ternary deep eutectic solvent, DES2 (consisting of choline chloride, citric acid, and AlCl3·6H2O in a molar ratio of 1:0.4:0.08), was synthesized. Raw elephant grass (EG) was pretreated with DES2, followed by sodium chlorite (NaClO2) bleaching and ultrasonic disruption to extract high-performance CNFs. The DES2 and NaClO2 treatments effectively removed hemicellulose and lignin, achieving removal rates of 99.23 % and 99.62 %, respectively, while maintaining a cellulose content of 78.3 %. DES2 demonstrated easy recyclability and maintained excellent biomass pretreatment performance even after multiple cycles. Following a brief 30-min intermittent ultrasound treatment, the resulting CNFs demonstrated superior crystallinity, increased carboxyl content, and a narrower width distribution compared to CNFs obtained from AlCl3-free DES1. Optimized conditions at 110 °C yielded CNFs with 85.3 % crystallinity, 0.64 mmol/g carboxyl content, 5.15 nm width distribution, and excellent dispersion in water for at least six months. Additionally, CNFs enhanced the tensile strength of chia seed mucilage (CM) composite films, showing a significant improvement to 26.6 MPa, representing a 231.3 % increase over the control film. This study offers a promising approach for efficiently producing CNFs from raw plants.

Extraction of humic acid from peat and lignite and the thermal behavior of their mixtures with ammonium nitrate

Due to the positive effect on soil structure and the influence on improving the efficiency of plant roots nutrient uptake, humic acids (HA) are widely considered for fertilizer production. Especially, it seems to be particularly promising to use them as additives in technologies of mineral fertilizer production. One of the common mineral fertilizer components, due to its good water solubility and the presence of nitrogen in two forms, is ammonium nitrate (AN). The aim of this study was to determine the influence of the humic acids extracted from peat and lignite on the thermal decomposition of HA and the thermal decomposition of ammonium nitrate and humic acids mixtures. For the quality assessment of HA, spectroscopic methods (FTIR/ATR and CP/MAS 13C NMR) and analysis of elemental composition were used. The analysis of the spectra showed differences in the degree of humification of humic acids extracted from various raw materials. HA isolated from peat were distinguished by the presence of peptides, polysaccharides, and lignin residues. Elemental analysis showed the higher carbon and sulfur content in the extracted HA compared to the reference samples. The results of the TG-DTA-MS analysis confirmed the influence of differences in the molecular structure of humic acids, especially in the aliphatic and aromatic carbon content, on the thermal decomposition process. Total content of carboxylic and/or hydroxylic functional groups had a significant impact on the start of the decomposition temperature. Their increase visibly influenced the acceleration of the exothermic decomposition of AN.

Preparation and characterization of achira starch oxidized by different concentration of sodium hypochlorite

AbstractIn this study, achira (Canna edulis) starch was oxidized by sodium hypochlorite and the effects of different concentration of oxidation agent (1, 2, 3 and 5%) on the physicochemical properties, morphological properties and crystallinity of achira starch (AS) was investigated. The carbonyl and carboxyl content, starch colour parameters, swelling capacity, solubility, IR spectra, SEM and XRD of native and oxidized achira starch (OAS) were evaluated. IR spectra of oxidized starch samples showed a new absorption peak which was assigned to the characteristic peak of carbonyl C=O, proved that starch had been oxidized. At lower concentration of sodium hypochlorite, there was no clearly change on the morphology of OAS granules, however, at higher concentration of oxidant (5%), there were some indentations and cracks on the surface of OAS‐5 starch granules. Oxidation with sodium hypochlorite has no significant effect on the crystallinity of the starch. Both AS and OAS granules showed the typical B‐type X‐ray diffractogram, indicating that the oxidation occurred in the amorphous region. After treating with oxidized agent, content of carboxyl groups increased significantly, whereas content of carbonyl groups slightly increased. The total oxidation degree of OAS samples increased with the increase of the concentration of hypochlorite treatment. Oxidation with sodium hypochlorite clearly increased both the swelling capacity and solubility of achira starch. Whiteness of starch was also improved.

Carboxymethylated Rhizoma alismatis Polysaccharides Regulate Calcium Oxalate Crystals Growth and Reduce the Regulated Crystals' Cytotoxicity.

This study explored the effects of polysaccharides (RAPD) extracted from the traditional anti-stone Chinese medicine Rhizoma alismatis and their carboxymethylated derivatives (RAPs) on the crystal phase, morphology, and size of calcium oxalate (CaOx). It also determined the damaging ability of the regulated crystals on human renal tubular epithelial cells (HK-2). RAPD carboxymethylation with a carboxyl group (-COOH) content of 3.57% was carried out by the chloroacetic acid solvent method. The effects of -COOH content in RAPs and RAP concentration on the regulation of CaOx crystal growth were studied by controlling the variables. Cell experiments were conducted to explore the differences in the cytotoxicity of RAP-regulated crystals. The -COOH contents of RAPD, RAP1, RAP2, and RAP3 were 3.57%, 7.79%, 10.84%, and 15.33%, respectively. RAPs can inhibit the growth of calcium oxalate monohydrate (COM) and induce the formation of calcium oxalate dihydrate (COD). When the -COOH content in RAPs was high, their ability to induce COD formation was enhanced. In the crystals induced by RAPs, a high COD content can lower the damage to cells. In particular, the cytotoxicity of the crystals induced by RAP3 was the lowest. When the concentration of RAP3 increased, the cytotoxicity gradually increased due to the reduced size of the formed COD crystals. An interaction was observed between RAPs and crystals, and the number of RAPs adsorbed in the crystals was positively correlated with the -COOH content in RAPs. RAPs can reduce the damage of CaOx to HK-2 cells by regulating the crystallization of CaOx crystals and effectively reducing the risk of kidney stone formation. RAPs, especially RAP3 with a high carboxyl group content, has the potential to be developed as a novel green anti-stone drug.

A novel proxy to examine interspecific phosphorus facilitation between plant species.

Resource complementarity can contribute to enhanced ecosystem functioning in diverse plant communities, but the role of facilitation in the enhanced complementarity is poorly understood. Here, we use leaf manganese concentration ([Mn]) as a proxy for rhizosheath carboxylate concentration to explore novel mechanisms of complementarity mediated by phosphorus (P) facilitation. In pot experiments, we showed that mixtures involving Carex korshinskyi, an efficient P-mobilizing species, exhibited greater biomass and relative complementarity effect than combinations without C. korshinskyi on P-deficient soils. Compared with monocultures, leaf [Mn] and [P] of species that are inefficient at P mobilization increased by 27% and 21% when grown with C. korshinskyi (i.e. interspecific P facilitation via carboxylates) rather than next to another inefficient P-mobilizing species. This experimental result was supported by a meta-analysis including a range of efficient P-mobilizing species. Phosphorus facilitation enhanced the relative complementarity effect in low-P environments, related to a greater change in several facilitated species of their root morphological traits relative to those in monoculture. Using leaf [Mn] as a proxy, we highlight a vital mechanism of interspecific P facilitation via belowground processes and provide evidence for the pivotal role of P facilitation mediated by the plasticity of root traits in biodiversity research.

Novel Nanomaterials Made of Humic Substances from Green Composts and Chitosan Exerting Antibacterial Activity

Green compost represents a sustainable source of humic substances (HS), which are supramolecular associations of heterogeneous natural compounds bearing a variety of functional groups. Novel humic-chitosan nanoconjugates (NC) were synthesized by using HS from three green composts [coffee husks (HS-COF), artichoke residues (HS-CYN), and fennel residues (HS-FEN)]. Solid-state NMR spectra showed that HS-CYN and HS-FEN contained the largest relative amount of polysaccharidic and phenolic carbons, whereas HS-COF had the greatest relative content of alkyl and carboxyl groups. While size and z-potential of NC depended upon the HS origin, NC-HS-FEN revealed the greatest thermal stability, followed by NC-HS-CYN and NC-HS-COF. Scanning electron microscopy and transmission electron microscopy analyses suggested the formation of spherical nanoparticles only for NC-HS-FEN and NC-HS-CYN. This was explained by more stable conformations of HS-FEN and HS-CYN that enabled regular spherical nanoparticles, as assessed by high-pressure size-exclusion chromatography measurements. NC bioactivity against bacterial human pathogens was strain-specific, and the inhibition of bacterial development was attributed to the positive z-potentials that facilitated NC adhesion on bacterial cell walls, smaller nanosizes favoring cell penetration, and subsequent release in the cell of NC toxic components that altered microbial biochemical functions. This study indicates that not only novel NCs can be obtained by humic matter derived from recycled biomass, such as green compost, but they can also be employed as effective and sustainable antimicrobial agents.

Lipid -Lowering Effect of Polysaccharide (Pectin) of Viscum album L. Plant in Rats

Disturbances of lipid metabolism is a predisposing factor of cardiovascular diseases, which are accompanied by high mortality rates of the population - ischemic heart disease and ischemic stroke. Plant polysaccharides can be promising remedies for correction of lipid imbalance.
 In this regard, the aim of the study was to assess the hypolipidemic activity of polysaccharides isolated from the leaves of mistletoe.
 The test-object was the leaves of the white mistletoe (Viscum album L.) growing on the apple (Malus domestica Borkh.), and the pear (Pyrus communis L.). Polysaccharides (water-soluble polysaccharides and pectin substances) were quantitatively determined by the gravimetric method followed by reprecipitation from ethanol. The qualitative composition was evaluated by thin layer chromatography. Functional groups in polysaccharides were determined by titrimetric method. The hypolipidemic activity of the obtained polysaccharides was determined under oral administration at a dose of 100 mg / kg in Wistar rats by the change of the concentration of total cholesterol, triglycerides, LDL and HDL cholesterol. The change of the content of cholesteryl ester transfer protein and Niemann-Pick C1-Like1 protein was also determined.
 As a result, it was found that among the polysaccharides in the leaves of mistletoe, pectin substances are predominate, which belong to the group of low-esterified pectins. A significant content of free carboxyl groups in pectins from the leaves of mistletoe was also found. The study of hypolipidemic activity showed that, among the polysaccharides of mistletoe leaves, pectin substances exert a more pronounced effect on lipid metabolism, the use of which reduced the content of triglycerides, total cholesterol and LDL cholesterol with an increase in LDL cholesterol in rats, probably due to a decrease in the activity of cholesteryl ester transfer protein and Niemann-Pick C1-Like1 protein. At the same time, at the level of the trend, mistletoe pectins showed a higher level of activity than analogous compounds obtained from the leaves of host-plants. It should be noted that the severity of the pharmacological effect of mistletoe pectins did not depend on the host-plants.
 Thus, based on the obtained results, it can be assumed that pectins obtained from the mistletoe leaves can be a potentially effective and safety hypolipidemic agent.

Wood microchannels with multi-carboxyl groups for selective adsorption of Fe3+ from ionic liquids aqueous solution: Experimental and DFT study

Heavy metal contamination is widely present in the spinning field. Some heavy metal ions such as Fe3+ may accumulate in the coagulation bath using ionic liquids (ILs) as green solvents to prepare regenerated cellulose fibers (RCFs), which seriously affect the performance of RCFs and the subsequent regeneration of ILs. This study proposed a new strategy to selectively adsorb Fe3+ from ILs aqueous solution using carboxyl-functionalized wood microchannel (CW). The CW was optimized by citric acid concentration, reaction time, and temperature using carboxyl group contents as an indicator. The physic-chemical properties of CW were characterized, and its adsorption performance for Fe3+ was also evaluated in a water system. Furthermore, the adsorption selectivity of CW for Fe3+ and ILs was investigated. The results demonstrate that the CW had a high adsorption ratio for Fe3+ (94.73%), while that for ILs was 4.20%. The selective adsorption mechanism, in which the Fe3+ is mainly separated from ILs aqueous solution by complexation with carboxyl group, was confirmed by FTIR, XPS, MIP, and DFT calculation. Accordingly, this paper may provide a new strategy to selectively adsorb Fe3+ from ILs aqueous solution, thus offering an economical and efficient method for ILs recovery and water purification.

Sуnthesis of terpene–methacrylic acid copolymers and their effect on the stability of inorganic dispersions in the presence of cationic surfactants

Copolymers of methacrylic acid and natural terpene monomers (α-pinene; β-pinene; ∆3-karene) with the molecular weight of (0.3–0.5)∙104 and a content of carboxyl groups of 14.5–16.3 % were synthesized. For the synthesized copolymers, hydrodynamic radius and the Kuhn segment, which characterizes flexibility of a polymer chain, were determined, as well as the Huggins constant in aqueous and saline solutions, and concentration regions for formation of supramolecular structures. In the presence of a cationic surfactant (benzetonium chloride, Hyamine), depending on the concentration of copolymers in the system, polymer-surfactant complexes were formed in soluble and insoluble forms. It has been shown that the effectiveness of the stabilizing action of soluble complexes with respect to an aqueous dispersion of calcium carbonate increases with an increase in the content of nonpolar groups in the polymer chain. A cationic surfactant (Hyamine) has been proposed as a precipitant in the method for the quantitative determination of carboxyl-containing polymers in aqueous and saline media.

Study on the thermal release characteristics and the correlation transformation mechanism of microscopic active groups of oxidized coal combustion in a deep mined-out area

With the normalization of deep mining, the risk of residual coal spontaneous combustion (CSC) in deeply mined areas has gradually increased. To investigate the thermal characteristics and microgroup transformation mechanisms during the secondary oxidation of deep-well oxidized coal, a deep-well oxidation process was simulated in a synchronous thermal analyzer, and the thermal parameters of the oxidized coal were tested. The correlated transformation pathways of microscopic active groups was studied by electron paramagnetic resonance (EPR) and in situ diffuse reflectance (in situ FTIR) experiments during the reoxidation of oxidized coal. The results showed that with increasing deep-well ambient temperature and oxidation temperature, the characteristic temperature of coal gradually decreased, exothermic heat release gradually increased, and active aliphatic structures and -OH, -CHO and other active functional groups gradually accumulated and became distributed more uniformly. When the thermal conditions and oxidation temperature were very high (> 160 °C), the active free radicals in the oxidized coal were rapidly consumed, resulting in a gradual decrease in the characteristic temperature and heat release during the secondary oxidation process, while the contents of peroxy and carboxyl groups continued to increase. In the slow oxidation stage of oxidized coal, methyl groups were mainly transformed with hydroxyl and peroxide groups (r > 0.96), and the associated oxidative consumption of -CHO and -COOH mainly occurred in the rapid oxidation stage (r > 0.99). Geminal diols and peroxy groups are important intermediates in the coal–oxygen composite reaction process. With an increase in the deep-well temperature and initial oxidation temperature, the reoxidation tendency and heat release capacity of residual coal in the goaf gradually increased, and the risk of CSC intensified. The research results provide a theoretical reference for the prevention and control of coal fires in deep mines and play an important role in guiding environmental management and gas emissions reduction measures in mining areas.

Effects of culture pH on cell surface properties and biosorption of Pb(II), Cd(II), Zn(II) of green alga Neochloris oleoabundans

Microalgal biomass has been established as a promising biosorbent for heavy metal ion (HMI) removal from contaminated waters. In this study, the cell surface properties of green alga Neochloris oleoabundans grown at different culture pH, i.e., 7.5, 8.5, and 9.5, which are referred to as B-7.5, B-8.5, and B-9.5, respectively, were investigated. The biosorption of three HMIs, i.e., Pb(II), Cd(II) and Zn(II), were studied systematically by these three types of biomasses. The results of isothermal analysis indicate that the biosorption was monolayer surface adsorption. Based on the Sips model, which best fits the experimental data among the three tested isotherm models, the biosorption capacities of all the three tested HMI on different biomasses followed the order B-9.5 > B-8.5 > B-7.5. The algal biomass obtained at culture pH 9.5, i.e., B-9.5, exhibited the highest biosorption capacities of Pb(II), Cd(II), and Zn(II) at biosorption pH 6.0, which were 100.01, 43.92, and 32.43 mg/g, respectively, corresponding to 3.0, 3.3, and 2.3 folds of that exhibited by B-7.5. FTIR, SEM, EDS and XPS were employed for characterization of cell surface. The XPS analysis revealed higher content of carboxyl (COOH) group on the B-9.5 cell surface than B-7.5 and B-8.5, which might be responsible for the much higher biosorption capacity of HMI by B-9.5.

Degradation of Polyacrylates by One-Pot Sequential Dehydrodecarboxylation and Ozonolysis

We establish a synthetically convenient method to degrade polyacrylate homopolymers. Carboxylic acids are installed along the polymer backbone by partial hydrolysis of the ester side chains, and then, in a one-pot sequential procedure, the carboxylic acids are converted into alkenes and oxidatively cleaved. This process enables the robustness and properties of polyacrylates to be maintained during their usable lifetime. The ability to tune the degree of degradation was demonstrated by varying the carboxylic acid content of the polymers. This method is compatible with a wide range of polymers prepared from vinyl monomers through copolymerization of acrylic acid with different monomers including acrylates, acrylamides, and styrenics.

Effect of the chemical structure of carboxyl-containing polymers on precipitate morphology and carbonate dispersions stability

The influence of the molecular structure of carboxyl-containing polymers on their inhibitory and stabilizing effect in the precipitation processes was studied using a number of polymeric acids with different contents of carboxyl groups (X): polyacrylic acid (Mn = 5100 g-mol–1, X = 61.11 %), polymethacrylic acid (Mn = 5500 g-mol–1, X = 48.79 %), copolymer of methacrylic acid with turpentine terpene (α-pinene) (Mn = 350 g-mol–1, X = 14.54 %). It has been established that polyacid molecules slow down the process of crystal growth and recrystallization of the amorphous phase into more stable crystalline forms, which leads to a change in the morphology and structure of a carbonate precipitate. It has also been shown that polycarboxylic acids increase the colloidal stability of a mixed dispersion of carbonates and kaolin. The synergism of the stabilizing effect of mixtures of different hydrophobicity-polyacids was noted: in the presence of a mixture of polyacrylic acid with a copolymer of methacrylic acid with turpentine terpene, the stabilization effect increases 2 times compared to dispersion without additives and 1.4–1.8 times compared with individual components of the mixture.