NH_4＋和H_2O_2抑制臭氧氧化过程中溴酸盐形成的效能研究

通过纯水条件下的模拟研究,考察NH4＋和H2O2在单独和联用时对臭氧氧化过程中溴酸盐形成的抑制效能。结果表明,单独投加NH4＋能显著降低溴酸盐的生成量,并对水中臭氧浓度衰减无明显影响;投加H2O2大于0.20 mmol/L时,能在一定程度上抑制溴酸盐的形成,但加快了水中臭氧浓度的衰减;同时投加过量H2O2和NH4＋时,相对单独投加过量H2O2条件进一步抑制了溴酸盐的形成,但相对单独投加NH4＋条件却促进了溴酸盐的形成。     

芬顿法和湿式过氧化氢氧化法处理醇酮模拟水的研究

以醇酮模拟水为研究对象,系统考察了芬顿法和湿式过氧化氢氧化法主要因素的影响规律,其中包括H2O2加量、pH值、Fe2+加量、反应时间等。通过单因素实验分别得到较优的反应条件。在较优条件下,芬顿法使醇酮模拟水的COD去除率达到73.40%,B/C由原来的0.15提高至0.30;湿式过氧化氢氧化法使醇酮模拟水的COD去除率达到73.12%,B/C提高到0.36。两种处理方法较大的提高了醇酮模拟水的可生化性,为后续的深度处理创造了条件。     

Effects of calcium peroxide on arsenic uptake by celery (Apium graveolens L.) grown in arsenic contaminated soil

The ability of calcium peroxide (CaO₂) to immobilize As of contaminated soil was studied using pot and field experiments. In pot experiment, CaO₂ applied at 2.5 and 5 g kg⁻¹ significantly increased celery shoot weight and decreased shoot As accumulation, which was ascribed to the formation of stable crystalline Fe and Al oxides bound As and the reduction of labile As fractions in the soil. The labile As fractions were pH dependent and it followed a “V” shaped profile with the change of pH. In field experiment, the dose of CaO₂ application at 750 kg ha⁻¹ was optimal and at which the celery was found to produce the highest biomass (63.4 Mg ha⁻¹) and lowest As concentration (0.43 mg kg⁻¹). CaO₂ probably has a promising potential as soil amendment to treat As contaminated soils.     

Fenton氧化工艺在某化工园区集中式污水处理厂升级改造工程中的应用

针对江苏省某化工园区集中式污水处理厂出水COD和TP高于DB32/939—2006《江苏省化学工业主要水污染物排放标准》规定的排放限值的情况,采用Fenton氧化工艺对该污水处理厂装置进行升级改造。小试最佳工艺条件为:初始污水pH 3.0~3.5,H_2O_2(质量分数30%)加入量0.8 m L/L,FeSO_4·H_2O加入量0.8 g/L,反应时间120min,Fenton氧化反应结束后中和反应的适宜pH约为7.0。升级改造工程包括2套并联运行的处理能力各为10 km~3/d的Fenton氧化系统,装置稳定运行后最终控制H_2O_2加入量为150 L/h,FeSO_4·7H_2O溶液加入量为700 L/h,相应的处理后出水COD和TP分别稳定在60 mg/L和0.4 mg/L以下,可达标排放。每吨污水的处理药剂成本约为0.9元。     

A possible simplification of the Goss-modified Abraham solvation equation

Abraham solvation equations find widespread use in environmental chemistry and pharmaco-chemistry. Recently Goss proposed a modified Abraham solvation equation. For various partitioning processes, the present study investigates the consequences for the fit when the Abraham solvation parameter V is left out of this modified solvation equation. For air-organic solvent partition, the Abraham solvation parameter V can be omitted from the Goss-modified Abraham solvation equation without any loss of statistical quality. For air–water partitioning, organic biphasic system partitioning, as well as water-organic solvent partitioning, omitting the V parameter from the Goss-modified Abraham solvation equation leads to only a small deterioration of statistic quality.     

Chemisorption of hydrogen sulphide and methanethiol by light expanded clay aggregates (Leca)

Removal of volatile sulphur compounds from livestock waste air by biological air filtration may be enhanced by application of packing materials with reactive properties. In this study, light expanded clay aggregates (Leca®) was tested with respect to sorption and potential chemical degradation of H₂S, Methanethiol (MT) and Dimethyl sulphide (DMS). Leca was selected due to its content of minerals, including iron, and due to its high specific surface area. The performance of Leca was evaluated based on breakthrough curves and by comparing the difference between the inlet and outlet gas concentrations. Whereas DMS did not appear to be removed by Leca, both H₂S and MT were removed with variable efficiency depending on the specific conditions. Dimethyl disulphide (DMDS) and dimethyl trisulphide (DMTS) were demonstrated to be produced during the degradation process in relatively high yields. A comparison between ambient air and nitrogen gas conditions showed that the chemisorption of H₂S and MT did not necessarily need oxygen to be present. X-ray analysis of Leca showed an abundance of Fe₂O₃. It is therefore hypothesized that Fe₂O₃ in Leca can remove H₂S and MT by chemisorption. Both air velocity and moisture content clearly affected the capacity of Leca for removal of H₂S and MT. Lower removal is seen at higher air velocities, whereas higher moisture content enhances removal. However, chemisorption of MT by Leca appears to be limited above a threshold moisture level. Potential reaction mechanisms are discussed in relation to the observed effects. The results implicate that Leca can be used as a filter material with reactive properties provided that moisture content is controlled and that an adequate air velocity is used.     

Microwave Pretreatment for Enhancement of Phosphorus Release from Dairy Manure

Both the advanced oxidation process (AOP) using a combination of hydrogen peroxide addition and microwave heating (H₂O₂/microwave), and the microwave heating process were used for solubilization of phosphorus from liquid dairy manure. About 80% of total phosphate was released into the solution at a microwave heating time of 5 min at 170°C. With an addition of H₂O₂, more than 81% of total phosphate could be released over a reaction period of 49 h at ambient temperature. The AOP process could achieve up to 85% of total phosphate release at 120°C. The results indicated that both the microwave, and the AOP processes could effectively release phosphate from liquid dairy manure. These processes could serve as pretreatments for phosphorus recovery from animal wastes, and could be combined with the struvite crystallization process to provide a new approach in treating animal wastes.     

Treatment of dairy manure using the microwave enhanced advanced oxidation process under a continuous mode operation

The microwave enhanced advanced oxidation process (MW/H₂O₂-AOP) was used to treat dairy manure for solubilization of nutrients and organic matters. This study investigated the effectiveness of the MW/H₂O₂-AOP under a continuous mode of operation, and compared the results to those of batch operations. The main factors affecting solubilization by the MW/H₂O₂-AOP were heating temperature and hydrogen peroxide dosage. Soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFA) increased with an increase of microwave (MW) heating temperature; very high concentrations were obtained at 90°C. Insignificant amounts of ammonia and reducing sugars were released in all runs. An acidic pH condition was required for phosphorus solubilisation from dairy manure. The best yield was obtained at 90°C with an acid dosage of 1.0 %; about 92 % of total phosphorus and 90 % of total chemical oxygen demand were in the soluble forms. The MW/H₂O₂-AOP operated in a continuous operation mode showed pronounced synergistic effects between hydrogen peroxide and microwave irradiation when compared to a batch system under similar operating conditions, resulting in much better yields.     

Atrazine removal by ozonation processes in surface waters

Abstract

Atrazine (6‐chloro‐N‐ethyl‐N'‐isopropyl‐1,3,5‐triazinedyl‐2,4‐diamine) was treated with ozone alone and in combination with hydrogen peroxide or UV radiation in three surface waters. Experiments were carried out in two bubble reactors operated continously. Variables investigated were the ozone partial pressure, temperature, pH, mass flow ratio of oxidants fed: hydrogen peroxide and ozone and the type of oxidation including UV radiation alone. Residence time for the aqueous phase was kept at 10 min. Concentrations of some intermediates, including deethylatrazine, deisopropylatrazine and deethyldeisopropylatrazine, were also followed. The nature of water, specifically the alkalinity and pH were found to be important variables that affected atrazine (ATZ) removal. Surface waters with low alkalinity and high pH allowed the highest removal of ATZ to be reached. There was an optimum hydrogen peroxide to ozone mass flow ratio that resulted in the highest ATZ removal in each surface water treated. This optimum was above the theoretical stoichiometry of the process. Therefore, to reach the maximum removal of ATZ in a O₃/H₂O₂ process, more hydrogen peroxide was needed in the surface waters treated than in ultrapure water under similar experimental conditions. In some cases, UV radiation alone resulted in the removal of ATZ higher than ozonation alone. This was likely due to the alkalinity of the surface water. Ozonation and UV radiation processes yield different amounts of hydrogen peroxide. Combined ozonations (O₃/H₂O₂ and O₃/UV) lead to ATZ removals higher than single ozonation or UV radiation but the formation of intermediates was higher.     

Short‐Term Effects of Hydrogen Fluoride on Nicotiana tabacum L

Data on the short‐term effects of fumigation with hydrogen fluoride (HF) on the response behavior of the Nicotiana tabacum L. cv. St. Karabalar 6265 are being presented. Growth rate, fluoride accumulation in leaves and soils, and degradation in chlorophyll and nicotine contents of the plant species against the variations in two experimental factors, namely the exposure concentration and exposure time parameters, were investigated. Resulting data reveals that the variety selected for this study is not so tolerant to fluoride as generally reported in the literature, if only the individual effects of the pollutant is considered.