Review of the kinetics of alkaline degradation of cellulose in view of its relevance for safety assessment of radioactive waste repositories

The degradation of cellulose (a substantial component of low- and intermediate-level radioactive waste) under alkaline conditions occurs via two main processes: a peeling-off reaction and a basecatalyzed cleavage of glycosidic bonds (hydrolysis). Both processes show pseudo-first-order kinetics. At ambient temperature, the peeling-off process is the dominant degradation mechanism, resulting in the formation of mainly isosaccharinic acid. The degradation depends strongly on the degree of polymerization (DP) and on the number of reducing end groups present in cellulose. Beyond pH 12.5, the OH^- concentration has only a minor effect on the degradation rate. It was estimated that under repository conditions (alkaline environment, pH 13.3-12.5) about 10% of the cellulosic materials (average DP = 1000-2000) will degrade in the first stage (up to 10⁵ years) by the peeling-off reaction and will cause an ingrowth of isosaccharinic acid in the interstitial cement pore water. In the second stage (10⁵-10⁶ years), alkaline hydrolysis will control the further degradation of the cellulose. The potential role of microorganisms in the degradation of cellulose under alkaline conditions could not be evaluated. Proper assessment of the effect of cellulose degradation on the mobilization of radionuclides basically requires knowing the concentration of isosaccharinic acid in the pore water. This concentration, however, depends on several factors such as the stability of ISA under alkaline conditions, sorption of ISA on cement, formation of sparingly soluble ISA-salts, etc. A discussion of all the relevant processes involved, however, is far beyond the scope of the presented overview.     

高浓度废水处理技术在柴油碱渣处理中的应用

炼厂柴油碱渣废水中含有成分复杂的酚及硫化物,因而其浓度较高。大港石化公司运用高浓度废水处理技术进行生物前期处理,其装置试运及柴油碱渣标定应用表明该技术先进。在生物处理过程中,工艺系统运行安全可靠,各项技术指标都达到或超过设计目标。其中,CODCr由处理前的34744mg/L降低到370mg/L,氨氮控制在50mg/L以下。高浓度废水处理技术流程简单,对周边环境无污染。     

炼油厂废催化裂化催化剂的再生技术

对炼油厂重油催化裂化过程硅铝催化剂朱活的原因进行了分析研究,提出了回流浸取法再生催化剂的新工艺。采用该工艺处理后的催化剂含镍量可由０．８％降至０．２１％,活性恢复９５．７％,达到工业应用标准。     

NaCl在Zn(Ⅱ)-NaOH-H_2O体系中溶解度的测定及去除

等温溶解平衡法测定了283.2～323.2 K温度范围内NaCl在Zn(Ⅱ)-NaOH-H2O体系(cZn(Ⅱ)=0.6 mol/L、cNaOH=5.00mol/L)及NaOH-H2O体系(cNaOH=5.00 mol/L)中的溶解度。与NaOH-H2O、纯水体系相比,相同温度下NaCl在Zn(Ⅱ)-NaOH-H2O体系中溶解度最小。运用正交实验法对Zn(Ⅱ)-NaOH-H2O体系中NaCl的溶解度进行因素分析。结果表明,较高的cNaOH和cZn(Ⅱ)是造成NaCl溶解度急剧降低的主要原因,提高温度虽然对NaCl的溶解有促进作用但影响较小。最后,通过加热浓缩方式提高溶液NaOH和Zn的浓度,促使NaCl因溶解度骤降而结晶析出,首次实现了碱锌溶液中高浓度Cl-的大量去除。实验结果具有重要的工程应用价值。     

电路板蚀刻废液及其回收铜盐产品中PCBs污染特征

POPs(持久性有机污染物)是近年来广受关注的一类环境污染物. 为研究工业过程中POPs的运转迁移,针对电路板蚀刻废液及其回收后生产的铜盐产品中7种指示性PCBs(多氯联苯)及CB-209进行分析. 结果表明,PCBs在碱性废液和微蚀废液中未检出,而在酸性废液中有不同程度检出,ρ(∑₈PCBs)在0.41~60.80 ng/L之间,其中ρ(∑₇指示性PCBs)在0.24~58.00 ng/L之间. 3种铜盐产品〔CuCl₂、Cu₂(OH)₃Cl和CuSO₄〕中,CuSO₄中w(∑₈PCBs)相对较高,在2.75~284.00 ng/kg之间;而CuCl₂中w(∑₈PCBs)在6.95~31.50 ng/kg之间;Cu₂(OH)₃Cl中w(∑₈PCBs)在7.31~9.42 ng/kg之间. 污染物指纹特征表明,酸性蚀刻废液及其铜盐产品中的PCBs具有十分相似的分布特征,CB-28是最主要的检出单体,并且w(CB-209)相对较高,表明铜盐产品中的PCBs主要来源于生产原料(酸性蚀刻废液)的携带,而酸性蚀刻废液中污染物来源须待进一步分析研究.      

Optimization of methyl orange removal from aqueous solution by response surface methodology using spent tea leaves as adsorbent

The effective disposal of redundant tea waste is crucial to environmental protection and comprehensive utilization of trash resources. In this work, the removal of methyl orange （MO） from aqueous solution using spent tea leaves as the sorbent was investigated in a batch experiment. First, the effects of various parameters such as temperature, adsorption time, dose of spent tea leaves, and initial concentration of MO were investigated. Then, the response surface methodology （RSM）, based on Box- Behnken design, was employed to obtain the optimum adsorption conditions. The optimal conditions could be obtained at an initial concentration of MO of 9.75 mg·L-1, temperature of 35.3℃, contact time of 63.8 min, and an adsorbent dosage 3.90 g· L-1. Under the optimized condi- tions, the maximal removal of MO was 58.2%. The results indicate that spent tea leaves could be used as an effective and economical adsorbent in the removal of MO from aqueous solution.     

焙烧条件对废干电池中汞的释放影响研究

在小型管式炉中进行废干电池的焙烧实验,分析了焙烧温度、时间及其交互作用对汞释放的影响.结果表明,焙烧时间对汞释放影响最大,温度也有显著影响,它们对汞释放有交互作用且作用显著,废干电池焙烧过程中汞在低温下更易释放.在温度650 ℃,焙烧时间120 min情况下,汞释放率达99%以上.焙烧前后干粉的X衍射分析结果表明,焙烧后电池中含有的晶态物增加,结构更复杂.     

离子色谱法同时测定水中总氮和总磷

采用碱性过硫酸钾消解—离子色谱法同时测定水中总氮和总磷的含量。该方法避免了国标法中过硫酸钾和氢氧化钠对吸光度的干扰,对总氮和总磷测定的精密度有很大的提高。该方法在实验测定的浓度范围内总氮和总磷的相对标准偏差分别为3.84%和4.24%;总氮和总磷的最低检出限分别为0.007 mg/L和0.009 mg/L,比国标法更低;对实际试样总氮和总磷的加标回收率分别为92.6%～105.3%和94.7%～100.2%。     

Prenatal diagnosis of infantile hypophosphatasia

Prenatal diagnosis was attempted in a pregnant Japanese woman whose son had died of infantile hypophosphatasia, using chorionic villi sampled at 10 weeks of gestation. Southern blot analysis of restriction fragment length polymorphism was used as a guide, with cDNA for the human liver-type alkaline phosphatase as a probe, and BclI as a restriction enzyme. The fetus was found to be a heterozygote; the pregnancy was allowed to continue; and the baby born was phenotypically normal.     

碱渣缓和湿式氧化处理工艺的工业应用

在碱精制过程中,会产生高污染物含量的碱渣,其中COD、硫化物和酚的排放量占炼油厂污染物排放量的20%～70%。它不仅是炼油厂的主要恶臭污染源,而且还直接影响了污水处理设施的正常运转和污水处理合格率。为了解决这一难题,抚顺石油化工研究院结合我国国情,针对碱渣的特性、开发了缓和湿式氧化工艺,并在上海、安庆、大庆、湛江及长岭等石化企业推广应用,取得了满意的效果。实践表明:采用缓和湿式氧化工艺处理碱渣可使其中的硫化物含量小于5mg/L,同时降低COD和酚的含量。