A Visible-Light-Promoted C-H Arylation and Heteroarylation of Uracil Derivatives with Diazoniums in Aqueous Conditions.

The photoredox synthesis of C-5 (hetero)arylated uracil and uridine substrates with the corresponding diazonium salts is described. The coupling proceeds efficiently without protection of the hydroxyls at the ribose or pre-functionalization of the C5 position at the nucleobase. No transition-metal catalyst is used in this transformation, thereby avoiding metal contamination in the final products. The use of water as the medium also eliminates the impurities caused by the use of organic solvents. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Synthesis of 5-aryl and 5-heteroaryl uracil derivatives Basic Protocol 2: Synthesis of 5-aryl uridine and deoxyuridine uridine derivatives.

[Cd Pollution and Safe Planting Zoning in Paddy Soils: A Case Study in a District of Chongqing].

Rice has a strong ability to accumulate Cd in soil, and it is of great significance to study Cd pollution and safe planting zoning in paddy soils. In this work, 300 sets of paddy soil-rice samples were simultaneously collected in 22 towns in a District of Chongqing, and soil pH, soil total and available Cd contents, and brown rice Cd contents were determined. Soil Cd pollution was assessed using the geoaccumulation index, bioconcentration factor, and the single-factor pollution index. Based on the Cd pollution indices of soil and brown rice, safe planting zoning for rice was determined. The results showed that the paddy soils were generally acidic, and total Cd contents ranged from 0.09 mg·kg-1 to 1.60 mg·kg-1, with 35.0% of sites exceeding the risk screening value. The Cd contents of the brown rice ranged from 0.002 mg·kg-1 to 0.808 mg·kg-1 and exceeded the food safety limit in 13.7% of cases. Pearson correlation analysis showed that the Cd content of brown rice was significantly positively correlated with soil total and available Cd (P<0.01). The pollution evaluation indicated that significant Cd accumulation occurred in the paddy soils, with some areas showing light-to-moderate pollution levels. The enrichment coefficients of rice to soil Cd ranged from 0.004 to 1.72. Overall, the paddy soils in the studied area were considered generally safe with respect to Cd pollution, with low-risk areas distributed in the south, west, and east, whereas some medium-high risk areas were detected in eight towns.

Aqueous and Visible-Light-Promoted C-H (Hetero)arylation of Uracil Derivatives with Diazoniums.

Direct C5 (hetero)arylation of uracil and uridine substrates with (hetero)aryl diazonium salts under photoredox catalysis with blue light was reported. The coupling proceeds efficiently with diazonium salts and heterocycles in good functional group tolerance at room temperature in aqueous solution without transition-metal components. A plausible radical mechanism has been proposed.

[Partial Nitritation and Anaerobic Ammonia Oxidation Synergistic Denitrification to Remove Nitrogen and Carbon from Domestic Sewage].

A sequencing batch reactor-anaerobic sequencing batch reactor(SBR-ASBR) process was used to treat domestic sewage. In the SBR, the effects of the anoxic/aerobic time ratio and temperature on the realization of partial nitritation(PN) were investigated. In the ASBR, the effects of different COD/NO2--N(C/N) ratios on the removal of nitrogen and carbon using anaerobic ammonia oxidation(ANAMMOX) and denitrification were studied. The results illustrated that:① After three single cycles and on the 22nd day, the NO2--N accumulation rate(NiAR) was 98.06%, and the nitrate nitrogen generation rate(SNiPR, calculated as N/VSS) was 0.28g·(g·d)-1, and simultaneous nitrification and denitrification removal the TN and COD were 12.29 and 110.36mg·L-1, respectively(temperature=25℃, anoxic/aerobic time ratio=30 min:30 min). ② At an anoxic/aerobic time ratio of 30 min:30 min, the filamentous sludge bulked, the sludge activity decreased, and sludge settleability was poor at 15℃. Furthermore, the conversion rate of NH4+-N to NO2--N was 86.83%, indicating that the effluent NH4+-N concentration was too low to provide suitable matrix concentrations for ANAMMOX at 30℃. The effluent concentrations of NH4+-N and NO2--N were 31.58 mg·L-1 and 35.04mg·L-1, respectively, matching the ratio of the ANAMMOX substrate at 25℃. ③ The SBR-ASBR combined process showed good denitrification performance; the effluent TN, NH4+-N, and COD concentrations were stable at 13.13, 4.83, and 69.96mg·L-1, respectively, and the removal rates were 83.10%, 93.64%, and 75.11%, respectively. When the influent C/N of the ASBR was 2.5, 2.0, and 1.5, respectively, anaerobic ammonia oxidation and denitrification showed the best performance with respect to nitrogen and carbon removal with a C/N of 2.0. The effluent NH4+-N, NO2--N, NO3--N, and COD were 0.09, 0.25, 1.04, and 32.73 mg·L-1, respectively.

[Electrocatalytic Oxidation of Sulfadiazine with Ni-Doped Sb-SnO2 Ceramic Ring Particle Electrode].

The excessive use and abuse of antibiotics has brought about serious threats to water environmental safety and human health. It is necessary to develop efficient, cheap, and environmentally friendly treatment technologies for antibiotics. In this work, a Ni-doped Sb-SnO2 microporous ceramic ring particle electrode was prepared by the dipping method and characterized by scanning electron microscopy, energy dispersion spectroscopy, and X-ray diffraction. The electrocatalytic oxidation ability and kinetic characteristics of sulfadiazine (SDZ) were studied using the prepared electrode, and the degradation pathways of SDZ were analyzed preliminarily. The results showed that Ni and Sb-SnO2 crystals were loaded on the particle electrode surface, which is beneficial for electron transfer and SDZ adsorption and improvement of electrocatalytic oxidation efficiency. Under the conditions of 0.02 mol·L-1 NaCl solution (pH 8), 15 mA·cm-2 of current density, and 15 g particle electrode, 50 mg·L-1 SDZ could be completely removed on the three-dimensional electrode within 15 min. The removal efficiency of TOC in the reaction solution reached 80.8% for 3 h degradation and was 17.6% higher than that with two-dimensional electrode. The kinetic process of the electrocatalytic oxidation could be well described by the first-order reaction kinetic model, and the rate constant was 0.329 min-1. The degradation products of SDZ were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the possible pathways of electrocatalytic degradation mainly include the fractures of S-N bond on sulfamido and C-N bond on pyrimidine ring, desulfonation, deamination, and·OH oxidation.

[Effect of HRT on Denitrifying Phosphorus and Nitrogen Removal in Modified A2/O-BAF].

The effect of hydraulic retention time (HRT) on denitrifying phosphorus and nitrogen removal in a modified two sludge A2/O-BAF system was studied. The influent COD, NH4+-N, and TP were 189.6, 60.4, and 5.1 mg·L-1, respectively. When HRT was 9, 8, 7, and 6 h, the average effluent COD was less than 42 mg·L-1. The average effluent NH4+-N levels were 2.4, 2.8, 3.3, and 6.5 mg·L-1, respectively. The average effluent TP values were 0.3, 0.4, 0.7, and 0.8 mg·L-1, respectively. The ratio of the denitrifying phosphorus accumulation organisms (DPAOs/PAOs) in the system of anoxic zone was reduced from 76.8% to 48.8%. When HRT was 8 h, the ratio of denitrifying phosphorus to nitrogen (ΔPO43-/ΔNO3--N) was increased by 37.5% by a mathematical statistics method. The ΔPO43-/ΔNO3--N in the anoxic zone was 1.24 (the theoretical value is 1.41). At this time, the effect of denitrifying phosphorus to nitrogen was the best. The SVI value was lower than 100 mL·g-1 throughout the experiment, and the MLVSS/MLSS gradually decreased from 0.74 to 0.63, indicating that the sludge activity was reduced.

[Short-cut Nitrification Start-up and Optimization of Operating Conditions Under Different Control Strategies].

Low C/N domestic sewage was treated in a SBR. With an operating temperature of (25±0.5)℃, NO2--N accumulation rates reached 96.79%, 98.80%, and 98.78% after 69, 63, and 58 cycles, respectively. In each case, alternating modes of hypoxia/aerobic (four times), aerobic/anoxic (five times), and aerobic/anoxic (four times) were applied, respectively, with an alternating time of 30 min. At the same temperature, when the aerobic/anoxic time ratios were 30 min:30 min, 40 min:20 min, and 30 min:60 min, and the single-cycle alternating times were 5, 3, and 5, respectively, stable NO2--N accumulation rates reached 98.81%, 97.71%, and 94.64% after 63, 73, and 78 cycles, respectively. The activity of AOB was 96.30, 99.27, and 102.26, respectively. Simultaneous nitrification and denitrification occurred under the three aerobic/anoxic time ratios. The total amounts of nitrogen removed by synchronous nitrification and denitrification were 29.89, 28.77, and 29.78 mg·L-1. When temperatures were adjusted to 18, 25, and 30℃, and when the aerobic/anoxic time ratio was 30 min:30 min, the NO2--N accumulation rates were 99.58%, 99.21%, and 95.93% after 90, 64, and 61 cycles, respectively. The activity of the sludge (f) peaked when after 64, 40, and 48 cycles, while the sludge-settling performance was good.

Iodide/H2O2 Catalyzed Intramolecular Oxidative Amination for the Synthesis of 3,2'-Pyrrolidinyl Spirooxindoles.

An ammonium iodide/hydrogen peroxide-mediated intramolecular oxidative amination of 3-aminoalkyl-2-oxindoles was achieved, affording the corresponding 3,2'-pyrrolidinyl spirooxindoles and their 6- or 7-membered analogous in moderate to high yields. This metal-free procedure features very mild reaction conditions, non-toxicity and easily handled hydrogen peroxide as a clean oxidant.

Ruthenium-Catalyzed Decarboxylative C-H Alkenylation in Aqueous Media: Synthesis of Tetrahydropyridoindoles.

We disclose herein a Ru(II)-catalyzed decarboxylative and oxidative coupling of N-substituted indolyl carboxylic acids with broad substrate scope in an aqueous solution. This method provides a sustainable and efficient access to synthesize various indole-fused cyclohexanyl acetic acids under mild conditions.