Peracetic acid as a single endodontic irrigant: effects on microhardness,roughness and erosion of root canal dentin

The aim was to assess the effects of 1% peracetic acid (PAA) as a single endodontic irrigant on microhardness, roughness, and erosion of root canal dentin, compared with 2.5% sodium hypochlorite (NaOCl) and with 2.5% NaOCl combined with 17% EDTA. Forty human, single‐rooted tooth hemisections were submitted to Knoop microhardness test, before and after the following irrigation protocols: PAA = 1% PAA; NaOCl = 2.5% NaOCl; NaOCl‐EDTA‐NaOCl = 2.5% NaOCl +17% EDTA +2.5% NaOCl; and SS = saline. Another 40 roots were instrumented, irrigated with the same protocols, and sectioned longitudinally. The roughness analysis was performed on the mesial section using a confocal laser scanning microscope, whereas erosion was analyzed on each third of the distal section, using a scanning electron microscope. The data were analyzed using ANOVA and Tukey post‐tests, and Kruskal‐Wallis and Dunn post‐tests (α = .05). The PAA and NaOCl‐EDTA‐NaOCl groups showed no significant differences (p > .05); both promoted reduction in microhardness and increase in roughness, compared with the NaOCl and SS groups (p < .05). NaOCl‐EDTA‐NaOCl promoted higher erosion in the cervical and middle thirds than the other groups (p < .05); there was no difference among PAA, NaOCl, and SS (p > .05). There was also no difference among the groups regarding the apical third (p > .05). PAA used as a single endodontic irrigant caused reduction in root canal dentin microhardness and increase in roughness in a similar way to NaOCl‐EDTA‐NaOCl; however, PAA caused less erosion than NaOCl‐EDTA‐NaOCl.     

富硒低钠盐中碘含量的测定

目的探讨富硒低钠加碘盐中碘含量的测定方法。方法通过不同的实验条件,优化国标GB/T13025.7-2012《制盐工业通用试验方法碘的测定》中氧化还原滴定法中的试剂用量,检测出富硒低钠加碘盐中的碘含量。结果改变碘化钾溶液量、淀粉溶液量、磷酸-草酸溶液量均无法测定富硒低钠盐中的碘含量;只有当次氯酸钠溶液用量≥5mL时,加入碘化钾溶液,才可以使富硒低钠加碘盐溶液显色,然后通过实验确定次氯酸钠的最佳用量,再滴定测定碘含量。结论富硒低钠加碘盐中含有还原性物质,测定其碘含量需加大次氯酸钠溶液的用量。     

Thermo-economic analysis of chlor-alkali electrolysis for hydrogen production in the electrochlorination plant: Real case

This study deals with the implementations of electrochemical technology for the on-site production of sodium hypochlorite (NaOCl) and hydrogen from seawater for utilization in the steam power plant. The effects of electrical current and seawater temperature on the performance of electrochlorination system are investigated. The obtained results show that current efficiency increases with increasing electrical current. The current efficiency of the system is calculated as 94% at a maximum electric current with a value of 4000 A and maximum temperature with a value of 30 °C. Electricity consumption increases for the unit generation of available chlorine in the case of both enhancements of electrical current and seawater. Hydrogen generation is directly proportional to the variation of the electrical current. Also, improvement in seawater temperature provides more efficient hydrogen generation. Moreover, energy and exergy efficiencies of the whole system are positively affected by an increase of current. However, energy and exergy efficiencies are determined to be 50.4% and 3.04%, respectively, under the best operational conditions. Besides, the cheapest product cost of the hydrogen gas is calculated as $4.04/kg under the greatest electrical current and seawater temperatures.     

5万t/a尿素法水合肼装置试运行总结

对建设在海拔高、风沙大、紫外线辐射强、昼夜温差大等自然条件下的5万t/a尿素法水合肼生产装置试运行中存在的问题（设备和管道衬里龟裂、变形,次氯酸钠冷却器堵塞,水合肼收率低,水合肼反应器结垢,DTB结晶器堵塞）,进行了分析、改造.改造后,装置达到了平稳、长周期运行的目标,且各项消耗和产能接近设计要求.     

工业次氯酸钠溶液中氯酸钠含量的测定

利用次氯酸钠和氯酸钠的氧化能力不同,以双氧水消解次氯酸钠的影响,以硫酸中和次氯酸钠溶液中的氢氧化钠,以硫酸亚铁作还原剂,将试样中的氯酸钠还原,再用重铬酸钾标准溶液氧化过量的硫酸亚铁,从而测定工业次氯酸钠溶液中氯酸钠的准确浓度.方法简单可靠,测得的回收率高,检测极限（质量浓度）可达0.05g/L以下.     

废次氯酸钠中乙炔的闪蒸回收及废液回用复配次氯酸钠

介绍了废次氯酸钠中乙炔气的闪蒸回收及废液回用复配次氯酸钠的工艺、实际生产情况,废液的回用可节约大量水资源,实现污水零排放。     

A new approach to evaluating the toxicity and genotoxicity of disinfected drinking water

The aim of this study was to evaluate the formation of toxic and genotoxic compounds in surface drinking waters treated with two widely used disinfectants, sodium hypochlorite (NaClO) and chlorine dioxide (ClO(2)), and a new disinfectant, peracetic acid (PAA). For this purpose a pilot plant was set up to add these biocides continuously to pre-filtered lake water flowing into three different basins. During three seasonal experiments, short-term in vivo tests (with plant, fish and molluscs) and in vitro tests (with bacteria, yeast and human cells) were carried out to evaluate the formation of genotoxic disinfection by-products (DBPs). Gas chromatography/mass spectrometry (GC/MS) was used to identify DBPs produced during the different treatments, microbiological analyses were performed to test the biocidal activity of the disinfectants, and chemical analyses were carried out to evaluate the quality of the water. The pilot drinking water plant under study was useful in studying the toxicity and genotoxicity of disinfected drinking water with this combined chemical/biotoxicological approach. This paper describes the setting up of the pilot plant and sets out/reports the results of the microbiological and chemical analyses.     

次氯酸钠清洗条件对PVDF微滤膜结构的损伤和性能的影响

为了了解次氯酸钠清洗对聚偏氟乙烯(PVDF)膜结构的损伤和性能的影响,借助正交试验和层次分析模型分析评价清洗条件对PVDF膜性能的影响,并对清洗过程中PVDF膜面变红的现象进行探讨.正交试验选择了清洗浓度、清洗时间和pH 3个清洗条件.结果表明,次氯酸钠的pH对PVDF膜的平均孔径和比通量影响最大,清洗时间对接触角的影响最大,而次氯酸钠浓度对洗脱液的总有机碳(TOC)影响最大.借助层次分析模型获得了正交试验范围内对PVDF膜性能损伤最小的清洗条件为:清洗液中次氯酸钠质量分数0.1％,清洗时间25 h和pH=9.次氯酸钠清洗过程中,PVDF膜面颜色变红只与pH有关,而与次氯酸钠浓度无关,这主要是由于高的pH会造成添加剂聚乙烯吡咯烷酮(PVP)的溶解和PVDF结构的变化.     

Residues of different gel formulations on dentinal walls: A SEM/EDS analysis

The aim of this study was to evaluate the presence of residues of sodium hypochlorite gel, chlorhexidine gel, and EDTA gel on dentinal walls after canal preparation through chemical SEM‐ elemental chemical microanalysis (EDS) analysis. Forty‐eight single‐rooted teeth were selected. They had their crowns sectioned and were instrumented with a reciprocating system. The canals were irrigated with 5 mL of saline solution during root canal preparation. After instrumentation, the root canals were irrigated with 3 mL 17% EDTA followed by 1 min of ultrasonic passive activation (3× 20 sec) to remove the smear layer, and then irrigated with 3 mL of saline solution. The specimens were randomized into three groups (n = 12) according to the chemical substance that filled the root canal for 30 min: GI: 5.5% sodium hypochlorite gel; GII: 2% chlorhexidine gel; GIII: 24% EDTA gel; Negative control group: no substance was used. Then, the root canals were irrigated with 6 mL of saline solution followed by 1 min of ultrasonic passive activation (3× 20 sec). After ultrasonic activation, the canals were irrigated with 2 mL saline. The roots were sectioned, and the percentage of each chemical element present in the samples was analyzed through chemical SEM‐EDS microanalysis. All experimental groups showed a significantly higher percentage of chemical elements (Na and/or Cl) than the control group (P < 0.03). This in vitro study has shown that, regardless of chemical solutions used even after the final irrigation protocol, chemical residues of different substances remained attached to the root canal walls. Microsc. Res. Tech. 78:495–499, 2015. © 2015 Wiley Periodicals, Inc.     

Comprehensive recovery of metals from cyanidation tailing

Cyanidation tailing is the residue produced in gold plants which use cyanidation to extract gold. It can be used as a secondary resource to recover residual metals that are of great economic value. The cyanidation tailing investigated in this paper was obtained from Shandong Province, China. It contained valuable metals such as chalcopyrite, galena, sphalerite and pyrite. In this study, alkaline sodium hypochlorite was used as a regulator in the pretreatment stage. It was proved that the sodium hypochlorite played two roles in the flotation pulp: oxidant and pH regulator. On one hand, sodium hypochlorite oxidized cyanide to cyanate, eliminating the negative effect of residual cyanide towards the environment. On the other hand, with the pH of flotation pulp exceeding 10, sphalerite and pyrite were depressed enormously, which was beneficial to the recovery of chalcopyrite and galena. With the Cu–Pb bulk flotation flowsheet, the cyanidation tailing was processed to obtain qualified Cu concentrate with grade of 13.17% and recovery of 70.00% compared with the original Cu grade of 0.21%. The Cu–Pb tailing was processed to obtain qualified Zn concentrate with grade of 34.72% and recovery of 69.58% compared with the original Zn grade of 0.33%, constituting the comprehensive recovery routing for the cyanidation tailing.