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Coal-tar pitch (CTP) is a substance produced by ambient and/or vacuum distillation of high-temperature coal tar, although CTP has a large yield in China, however its wide application is limited due to its high toxicity. It was found that the toxicity of CTP was derived from its large amount of toxic Polycyclic Aromatic Hydrocarbons(PAHs) by 13C NMR and gas chromatography/mass spectrometer, including 16 PAHs monitored by the United States Environmental Protection Agency(EPA), such as fluoranthene、pyrene and benzo[a]pyrene. Various anti-toxic modification methods of CTP are introduced in the article, including chemical crosslinking method and physical chemistry method. The existing research mainly focuses on the former; by comparing the molecular structure of CTP and petroleum pitch, it is found that petroleum pitch has higher aliphatic hydrocarbons,it is proposed to add alkyl side chains to PAHs by alkylation of long-chain olefins to generate non-toxic long-chain alkyl substituted PAHs and inhibit the toxicity of CTP. Thus the method of alkylation cross-linking modification is focused on. The principle of the method and the catalysts used were summarized, the domestic and foreign related modification experiment results and theoretical research work were analyzed; Firstly, the alkylation of 16 kinds of PAHs with olefins was simulated by Gaussian, and the general rules of the reaction were obtained; Secondly, model compounds were selected for alkylation reaction, the possible reaction and its reaction mechanism of PAHs in the process of CTP modification were discussed; Finaly, the reaction conditions obtained from alkylation experiments of model compounds were applied to real CTP system, including 16 U.S. Environmental Protection Agency priority monitoring PAHs reduction in the modified coal tar pitch, as well as the changes of asphalt fume emissions and water soluble matter after modification in CTP, meanwhile the future research and application hot-spots and development of this method were prospected, it is hoped to provide reference for the environmental friendly utilization of CTP at home and abroad.

The treatment and resource utilization of solid waste and wastewater are becoming increasingly important. In this study, we propose a method to synthesize sulfur quantum dots using coked sulfur paste as raw material, which produced sulfur quantum dots with good water solubility, good dispersibility and stable luminescence performance. The synthesized sulfur quantum dots were used as a fluorescent probe for sensitively detecting low concentrations of silver ions (Ag+) based on the principle of fluorescence quenching. The detection method has a wide detection range (0–160 μM) with the lowest limit of detection of 7.1 μM and no quenching effect in the presence of 11 common ions, thus enabling the highly selective detection of silver ions. Moreover, a new method for the recovery of silver involving the strong bonding between sulfur quantum dots and silver ions was developed, i.e., even a low concentration of silver ions (under 200 μM) in industrial wastewater was converted into silver sulfide (Ag2S) and silver sulfate (Ag2SO4) for recovery. Results show that the average recovery rate reached 99.03% in the aqueous environment in the presence of five types of hetero-ions, namely, Na+, K+, Ca2+, Mg2+ and Al3+, showing both high efficiency and selectivity. This investigation realized the resourceful utilization of coked sulfur paste and provides a new pathway for the detection and recovery of low concentrations of silver in industrial wastewater. [ABSTRACT FROM AUTHOR]

CO2 mineralization plays a critical role in the storage and utilization of CO2. Coal fly ash (CFA) and red mud (RM) are widely utilized as CO2 mineralizers. However, the inert calcium species in CFA limit its carbonation capacity, meanwhile the substantial Ca2+ releasing of RM is hindered by a covering layer of calcium carbonate. In this study, CO2 mineralization in a composite system of CFA and RM was investigated to enhance the carbonation capacity. Multiple analyzers were employed to characterize the raw materials and resulting mineralization products. The results demonstrated that a synergistic effect existed in the composite system of CFA and RM, resulting in improving CO2 mineralization rate and efficiency. The produced calcium carbonate was ectopically attached the surface of CFA in the composite system, thus slowing down its coverage on the surface of RM. This phenomenon facilitated further releasing Ca2+ from the internal RM, thereby enhancing CO2 mineralization efficiency. Meanwhile, the inclusion of RM significantly improved the alkalinity of the composite system, which not only promoted the dissolution of Ca2+ of the inert CaSO4(H2O)2 in CFA, but also accelerated CO2 mineralization rate. The investigation would be beneficial to CO2 mineralization using industrial solid wastes. [ABSTRACT FROM AUTHOR]

Direct coal liquefaction residue is a coal waste with high ash and sulfur content, but also rich in valuable organic carbons. In this work, the ultraclean carbons were obtained by solvent extraction using petroleum ether at a mild temperature. The petroleum ether extractable fraction is ash-free with high carbon content, but low nitrogen and sulfur. The petroleum ether extractable fraction is reasonable to be cleaned for fuel use or converted into carbon products. Detailed characterizations on the chemical composition and structural features of petroleum ether extractable fraction were performed to supply fundamental information for additional treatment. [ABSTRACT FROM AUTHOR]

Oxidative depolymerization of low-rank coals is promising for obtaining benzene carboxylic acids (BCAs). However, it is hindered by the low yield of BCAs along with a large number of alphatic acids. Thermal dissolution could modify the physico-chemical structural features of low-rank coals, which is expected to improve the oxidation of LRCs. In this paper, lignite and subbituminous coal were firstly subjected to thermal dissolution with cyclohexane at 250 °C for 2 h. Then, the raw coal and the corresponding thermal insoluble portion (TIP) were oxidized by NaOCl under the same conditions. The residual yields of TIPs oxidation were both lower than those of raw coals oxidation, indicating that TIPs were more easily oxidized than the raw coals. The yield of BCAs obtained by TIPs oxidation was above 19% higher than that from the oxidation of raw coals. Meanwhile, the selectivity of BCAs was improved in the resulting oxidation products from TIPs compared with that from the raw coals. The relationship between BCAs generation and thermal dissolution of low rank coals was investigated by ultimate analysis, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The results suggested that thermal dissolution could enrich aromatic portion in the remaining TIPs, resulting in an increasing of the yield and selectivity of BCAs. Simultaneously, thermal dissolution raised the specific surface area and expanded the looser space structure of TIPS, which were beneficial for the sufficient collision between aromatic structures and oxidant, facilitating the oxidative depolymerization of TIPs. This investigation would provide a novel route for promoting BCAs production by mild oxidative depolymerization of low-rank coals. [ABSTRACT FROM AUTHOR]

• 2,5-Furandicarboxylic acid could be synthesized by direct carboxylation of the unedible-biomass derivant 2-furoic acid and the readily available formate. • The conversion of HCOOM to CO 2 •− is an effective way to achieve a carboxylation reaction. • The C(sp2)-H bond cleavage of HCOO− to generate H• and CO 2 •−is the rate-determining step. Furan-2,5-dicarboxylic acid (FDCA) is an important biomass-derived diacid, and it is the most promising substitute for terephthalic acid. The common method of FDCA usually involves 5-hydroxymethylfurfural oxidation. Edible fructose is often used as the feedstock of 5-hydroxymethylfurfural, and the oxidation step would generate undesirable impurities. Herein, FDCA was novelty synthesized by carboxylation of formate and 2-furoic acid (FA) derived from unedible-biomass. This route is potentially advantageous because it is simple to operate and does not require any additional additives. The reaction mechanism has been elucidated by density functional theory (DFT) calculations. In the carboxylation process, the C(sp2)-H bond of formate (HCOOM) undergoes cleavage, generating the carbon dioxide radical anion (CO 2 •−). Subsequently, CO 2 •− attacks the C 5 of FA, forming the C C bond and ultimately yielding FDCA. The conversion of HCOOM to CO 2 •− is an effective way to achieve carboxylation reaction. The rate-determining step of the carboxylation reaction is the cleavage of the C(sp2)-H bond of HCOO− with activation barrier of 159.11 kJ⋅mol−1. The investigation would provide a new strategy for the mechanism of carboxylation reactions, and hold the potential to establish pathways for FDCA production. [Display omitted] [ABSTRACT FROM AUTHOR]