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ABSTRACT4,6-dimethoxy-2-methylsulfonylpyrimidine (DMSP) is an important chemical intermediate which has been widely used in the synthesis of plant growth regulators, pesticides, and fungicides. However, the traditional synthetic manufacturing process involves highly toxic dimethylsulfate and highly corrosive phosphorus oxychloride, causing serious environmental problems. To overcome these problems, we utilized chloromethane instead of dimethylsulfate as a methylating agent to synthesize DMSP. The reaction was shortened to only2 steps. Since 4,6-dimethoxy-2-methylthiopyrimidine is the key intermediate in the synthesis of DMSP, it is of great importance to improve the conversion and selectivity. In this work, 4,6-dimethoxy-2-methylthiopyrimidine was synthesized from 2-thiobarbituric acid in the presence of potassium carbonate and chloromethane through a one-step procedure. By optimization of reaction conditions, high conversion of 2-thiobarbituric acid (85.7%) and selectivity of 4,6-dimethoxy-2-methyl thiopyrimidine (53.1%) were obtained. Compared to the traditional synthetic pathway, our new synthetic process is more economical and environment-friendly.

Sulfamethazine (SAT) is widely present in sediment, soil, rivers, and groundwater. Unfortunately, traditional water treatment technologies are inefficient at eliminating SAT from contaminated water. Therefore, developing an effective and ecologically friendly treatment procedure to effectively remove SAT is critical. This has raised concerns about its potential impact on the environment and human health. In this study, metal–organic–inorganic composites consisting of graphene-encapsulated Fe–Mn metal catalyst (Mn3Fe1–NC) were synthesized by calcining MnFe Prussian blue analogs (PBA) under a nitrogen atmosphere. The composites were applied to activate peroxymonosulfate (PMS) and facilitate the degradation of SAT in aquatic environments. The Mn3Fe1–NC, dosed with 5 mg, in combination with PMS, dosed with 1.5 mmol L–1, achieved a 91.8% degradation efficiency of SAT. The transformation of the CN skeleton led to the formation of a carbon shell structure, which consequently reduced metal ion leaching from the material. At various pH levels, the iron and manganese ions were observed to leach out at levels lower than 0.1392 and 0.0580 mg L–1, respectively. In contrast, the Mn3Fe1–NC was found to be minimally impacted by pH levels and coexisting ions present in the aqueous environment. Radical burst experiments and electrochemical analysis tests verified that degradation primarily occurs through the nonradical pathway of electron transfer. The active sites responsible for this process were identified as the Mn (IV) and graphitic-N atoms on the material, which facilitate direct electron transfer. Additionally, the presence of Fe atoms promotes the valence cycling of Mn atoms. This study introduces new insights into the reaction mechanism and the constitutive relationship of catalytic centers in nonradical oxidation reactions.

Ferrate (Fe(VI)) salts are commonly regarded as green and high efficient oxidants to eliminate organic contaminants. Current studies mainly focused on develop homogeneous activation technology or heterogeneous catalysts to promote Fe(VI) performances in contaminants degradation. Interestingly, this study disclosed that the degradation performance of tetracycline hydrochloride (TC) was enhanced by using in situ prepared ferrate supernatant (Fe(VI)s), and the oxidation performance and degradation mechanism were systematically explored by comparing with the ferrate precipitation (Fe(VI)p) and the commercial ferrate (Fe(VI)c). Results showed that the degradation rate of TC by Fe(VI)s reached to 98.5 % within 5 min, while the degradation rate of Fe(VI)p and Fe(VI)c were obtained less than 20 % in 30 min. Although degradation process of TC in these three system were all conformed to the pseudo-first-order reaction kinetic, the rate of degradation (Kobs) obtained in Fe(VI)s was 5.30 and 37.2 times higher than that in Fe(VI)c and Fe(VI)p, respectively. Electron paramagnetic resonance (EPR), radical quenching and PMSO probe experiments proved that Fe(IV)/Fe(V) were the main active species for TC degradation with Fe(VI)s, while ∙OH and ⋅O2−were the main active substance of Fe(VI)c. On the basis of the intermediates detected by LC-MS/MS analysis, a pathway for TC degradation was proposed. In addition, the toxicity of TC and its degradation products was evaluated by using the toxicity evaluation software tool. This study demonstrated efficient organic contaminant oxidation with in situ prepared ferrate solution (Fe(VI)s) and provided a comprehensive understanding of degradation process for pollutants removal.