Characterization of humic acids from original coal and its oxidization production

Five coal samples obtained from Chinese coal-producing areas were oxidized by hydrogen peroxide (H2O2), and humic acids (HAs) were derived from original coal and its oxidizition samples. HAs were characterized by physical and chemical methods, between which was also comparison. Yield, ash, aromaticity, molecular weight and functional group of HAs showed variance between original coals. While, yield, molecular weight, and the quantity of oxygen-containing groups of HAs increased more from coals oxidized with H2O2. However, the increase of oxygen-containing functional groups depended on original coals. For Yimin lignite, the oxidation of H2O2 could obviously improve the carboxyl group content of HAs, thus promoting the adsorption of nitrogen. This study demonstrated that oxidation of coal by using H2O2 was one pretreatment way to obtain and modify HAs which could be used as prerequisite and functional material in agricultural field.

Valorization of Rice Straw via Hydrotropic Lignin Extraction and Its Characterization

Rice straw hydrotropic lignin was extracted from p-Toluene sulfonic acid (p-TsOH) fractionation with a different combined delignification factor (CDF). Hydrotropic lignin characterization was systematically investigated, and alkaline lignin was also studied for the contrast. Results showed that the hydrotropic rice straw lignin particle was in nanometer scopes. Compared with alkaline lignin, the hydrotropic lignin had greater molecular weight. NMR analysis showed that β-aryl ether linkage was well preserved at low severities, and the unsaturation in the side chain of hydrotropic lignin was high. H units and G units were preferentially degraded and subsequently condensed at high severity. High severity also resulted in the cleavage of part β-aryl ether linkage. 31P-NMR showed the decrease in aliphatic hydroxyl groups and the increasing carboxyl group content at high severity. The maximum weight loss temperature of the hydrotropic lignin was in the range of 330–350 °C, higher than the alkaline lignin, and the glass conversion temperature (Tg) of the hydrotropic lignin was in the range of 107–125 °C, lower than that of the alkaline lignin. The hydrotropic lignin has high β-aryl ether linkage content, high activity, nanoscale particle size, and low Tg, which is beneficial for its further valorization.

A simple multi‐wavelength spectroscopic method for the determination of carboxyl group content in nanocellulose

This study describes a multi-wavelength spectroscopic method for the determination of carboxyl group content of nanocellulose. Methylene blue (MB) was used as a color indicator, which can bind to the carboxyl groups in nanocellulose to form a R-COOMB complex with a binding ratio of 1:1, although the spectrums of MB and R-COOMB at 500–750 nm are overlapped, and solid impurities could cause spectral interference. To solve these issues, a multi-wavelength spectroscopic measurement on a MB and nanocellulose mixture solution technique and mathematical model were developed, allowing the content of carboxyl groups in nanocellulose to be quantified. The results showed that the method has good measurement precision and accuracy as compared with those measured by a reference method. The method is simple and requires only a small sample size for testing and thus makes it suitable for nanocellulose related research and applications.

PREPARATION OF FLUORESCENT POLYSTYRENE MICROSPHERES BY IMPROVING SWELLING PERFORMANCE BASED ON MOLECULAR WEIGHT AND SURFACE CARBOXYL GROUP CONTENT

The fluorescent microspheres are prepared by the swelling-evaporation method. The optimal swelling conditions are obtained by researching related factors, such as types and dosages of swelling agent, dosages of fluorescent substance, swelling time and swelling temperature. Considering that the structure of microspheres can influence the swelling properties, the paper mainly focuses on the effect of molecular weight and surface carboxyl group content of polystyrene microspheres on swelling properties. When the molecular weight of microspheres is 75276 g mol-1, the density of carboxyl group on their surface is 6.94×10-4 mol g-1, and the doping amount of europium complex reaches the maximum of 24.9 mg g-1 with the strongest fluorescence intensity. Meanwhile, the as-prepared fluorescent microspheres have high monodispersity, uniform particles size and high thermal stability (the decomposition temperature is 385 oC), which sets up the good foundation for biomolecule detection. So, this work provides a significant experience for the preparation of fluorescent microspheres.

Synthesis of Controllable Carboxylated Polystyrene Microspheres by Two-Step Dispersion Polymerization with Hydrocarbon Alcohols

Carboxylated polystyrene (PS) microspheres were synthesized by the two-step dispersion polymerization of styrene in hydrocarbon alcohols (CnH2n+1OH,n=1–5) in the presence of acrylic acid (AA) as a functional comonomer, 2,2′-azobis-(2-methylbutyronitrile) (AMBN) as the initiator and polyvinylpyrrolidone (PVP55) as the dispersant. The effects of solvent type, AA concentration, and first reaction time on the carboxyl content on the microsphere surfaces were investigated. The PS microspheres were characterized by scanning electron microscopy, infrared spectroscopy, nuclear magnetic resonance, and gel permeation chromatography. The results showed that the first reaction time of the two-stage dispersion polymerization had a great influence on the nucleation process, and appropriately prolonging the first-step reaction time had a great influence on the surface carboxyl content. The effect of the solvent on the surface carboxyl content of PS microspheres was significant. With n-butanol as the solvent, the carboxyl group content on the surface of the microspheres reached 57.05 mg/g.

Preparation of Water-Soluble Carboxymethylated Lignin from Wheat Straw Alkali Lignin

Water-soluble carboxymethylated lignin (CML) was synthesized using wheat straw alkali lignin (WAL) in aqueous medium. The process of carboxymethylation was optimized with respect to the NaOH concentration, monochloroacetic acid concentration, reaction temperature and time. The optimized product has a yield of 80.47% and a carboxyl group content of 2.8231 mmol•g-1, respectively. The optimum conditions for carboxymethylation are NaOH concentration of 20.0% (wt%), monochloroacetic acid concentration of 37.5% (wt%), temperature of 70 °C and time of 90 min. The optimized CML was characterized by FTIR spectroscopy, 1H NMR spectroscopy and interfacial tension apparatus. The result shows that the substitution reaction of carboxymethylation occurs simultaneously in the phenolic hydroxyl group and aliphatic hydroxyl group in WAL. CML has the surface activity in water for industrial application as dispersant.

Sorption properties of periodate oxidized cotton

In this paper the effect of periodate oxidation on the chemical and sorption properties of cotton yarn was investigated by determining aldehyde group content, moisture sorption, water retention and iodine sorption. Oxidation of cotton yarn was performed by varying concentration of sodium periodate solution and reaction time. To measure the aldehyde content present in the oxidized cotton, the aldehyde groups were selectively oxidized to carboxyl groups with sodium chlorite at pH 4-5, at room temperature for 48 h, and carboxyl group content was determined by modified calcium-acetate method. Differences in the sorption properties of untreated and oxidized cotton samples were obtained using conventional methods. The aldehyde groups were introduced into the oxidized cotton up to 99.2 ?mol/g. Compared to the untreated fibers, oxidized cotton samples exhibited higher moisture sorption (up to 9 %) and lower water retention values (up to 19 %) and iodine sorption values (up to 31 %). Based on the obtained results, it can be concluded that the crystalline structure of cellulose is not significantly changed by periodate oxidation, which is of great importance for textile material production.

Binding of cadmium to soil humic acid as a function of carboxyl group content

The binding of Cd(II) to soil humic acid (HA) at pH 6.5 and in 0.1 mol/L KNO3 ionic medium, was studied by potentiometric titration with a cadmium ion selective electrode. The influence of carboxyl groups in cation-humic interactions was investigated by selective blocking of humic acid carboxyl groups with thionyl chloride and methanol. Infrared spectroscopic analysis confirmed that esterification took place. Differences between underivatized and derivatized HA complexation properties are ascribed to carboxyl groups. The Scatchard plots and incremental formation constants were used to obtain values for Cd-binding constants, for both HAs. The derivatization decreased the number of HA complexing sites by approximately 60 %, which correlates with acid-base properties of both HAs, studied by barium hydroxide and calcium acetate exchange methods. The stability constants for binding at the strongest sites (logKINT) was larger for underivatized HA (5.40) than for derivatized HA (4.92), indicating greater stability in the case when carboxyl groups are involved in complexation reaction.