Cyanide Detoxification of Mining Wastewaters with TiO2 Nanoparticles and Its Recovery by Electrocoagulation

Due to the widespread use of cyanide in mining operations, its recovery and destruction is important for both the environmental aspects of wastewater and its treatment, and the economic aspects associated with the high consumption of chemicals by the process itself. A photoelectrocatalytic detoxification technique with titanium dioxide microelectrodes is one of the most innovative ways for the treatment of wastewater containing cyanide. However, this technique has a disadvantage for industrial application in that the separation of titanium dioxide after the photocatalytic degradation of cyanide is rather difficult due to the fineness of the particles, and therefore, the reuse of the titanium dioxide has not been attained for the treatment of cyanide‐containing wastewater. To overcome this weak point, an electrocoagulation (EC) technique is used to recover the titanium dioxide from its aqueous suspensions. The results show that photodegradation of cyanide is 93 % in 30 min using a 450 W halogen lamp. The recovery of anatase with the EC process is 98 %. The results indicate that this technique has the potential to serve as a reliable and economical method because sunlight can be used efficiently as the power source. The Langmuir isotherm is used to obtain the thermodynamic parameters, i.e., free energy, enthalpy and entropy. The evaluation of these parameters, i.e., ΔG° = –37 kJ/mol, ΔH° = –54 kJ/mol and ΔS° = 0.524 kJ/mol K, indicates the spontaneous and exothermic nature of the adsorption of the anatase particles on the iron species.     

单扫描极谱法测定食品及水样中氰化物

为测定食品及水样中氰化物建立单扫描极谱法。通过仪器分析条件、不同介质及其用量的选择 ,探索氰化物出峰电位及峰形。在 0 0 1g mL硼砂溶液中 ,氰化物于 - 2 80mV(vs .SCE)附近产生一个清晰的极谱波峰。氰化物浓度在 0 0 5～ 5 μg mL范围内线性关系良好 ,相关系数 (r)为0 9992 ,相对标准偏差为 1 2 %～ 2 9% ,试样加标回收率 89 0 %～ 99 8%。所建立的方法用于食品及水样中氰化物的测定 ,结果令人满意。     

酒中微量氰化物的测定方法研究

目的　探讨国标法GB T 5 0 0 9 4 8异烟酸 -吡唑啉酮测定酒中氰化物产生浑浊的原因及其干扰因素 ,并对方法进行改进。方法　在pH7 0磷酸盐缓冲溶液中 ,氯胺T将氰化物氧化生成氯化氰 ,然后以十二烷基硫酸钠 (SLS)作增溶剂 ,在胶束条件下与异烟酸 -吡唑啉酮反应生成蓝色染料。结果　方法产生浑浊的原因主要是酒中乳酸乙酯成分所致。在 2 5g LSLS胶束条件下 ,成功地消除了浑浊及基质成分乙醇的影响 ,并对方法产生增溶、增敏、增稳作用。CN-的线性范围为 0～ 0 3mg L ,相关系数r=0 9995 ,最低检出浓度为 0 0 3mg L ,表观摩尔吸光系数 (ε)达 1 2 6× 10 5L (mol·cm)。回收率为 82 0 %～ 10 4 0 % ,RSD为 0 5 %～ 4 9% ,与吡啶 -巴比妥酸法比较 ,结果差异无显著性。结论　改进后的国标法用于酒中氰化物的测定 ,抗干扰力强、稳定性好、灵敏度高、准确度好。     

Accretion of Pollutants in Snow Exposed to Urban Traffic and Winter Storm Maintenance Activities. I

Urban snow is impacted by traffic activities and winter maintenance practices that result in significant accretion of dissolved, colloidal, and suspended solids in a complex heterogeneous snow matrix that includes heavy metals, inorganic, and organic compounds. Extended residence times of snow as a roadway snowbank exposed to these pollutant-generating activities lead to significant pollutant accretion and partitioning in the snow matrix. This study analyzed four highway sites in urban Cincinnati with respect to specific water quality indices for the residence time of roadway snow. Chloride levels in roadway snow illustrate a direct correlation to application of de-icing salts. While accretion of total dissolved solids (TDS) was initially rapid with a decrease late in the event, total suspended solids (TSS) accretion demonstrated a more gradually increasing trend for the duration of roadway snow, approaching 105?mg/L. Temporal trends towards increasing total chemical oxygen demand (CODt) exerted by roadway snow are similar to TSS, with CODt values approaching 105?mg/L. Applications of 2.2×105?kg of de-icing salt containing cyanide as an anticaking agent, along a 27-km section of interstate, resulted in approximately 6 kg of cyanide discharged along this major north-south interstate in the study area. Results indicate that traffic activities and winter storm management practices can have a significant impact on pollutant accretion in urban snow.     

Decontamination of industrial cyanide-containing water in a solar CPC pilot plant

The aim of this work was to improve the quality of wastewater effluent coming from an Integrated Gasification Combined-Cycle (IGCC) power station to meet with future environmental legislation. This study examined a homogeneous photocatalytic oxidation process using concentrated solar UV energy (UV/Fe(II)/H₂O₂) in a Solar Compound Parabolic Collector (CPC) pilot plant. The efficiency of the process was evaluated by analysis of the oxidation of cyanides and Total Organic Carbon (TOC). A factorial experimental design allowed the determination of the influences of operating variables (initial concentration of H₂O₂, oxalic acid and Fe(II) and pH) on the degradation kinetics. Temperature and UV-A solar power were also included in the Neural Network fittings. The pH was maintained at a value >9.5 during cyanide oxidation to avoid the formation of gaseous HCN and later lowered to enhance mineralization. Under the optimum conditions ([H₂O₂] = 2000 ppm, [Fe(II)] = 8 ppm, pH = 3.3 after cyanide oxidation, and [(COOH)₂] = 60 ppm), it was possible to degrade 100% of the cyanides and up to 92% of Total Organic Carbon.     

Role of the support on the activity of silica-supported TiO2 photocatalysts: Structure of the TiO2/SBA-15 photocatalysts

Immobilization of TiO₂ on silica materials has been commonly proposed in order to make easier the separation of the catalyst after the photocatalytic reactions in aqueous systems. The main drawback of the supported photocatalysts is that they usually show lower activities in comparison with powdered TiO₂ materials. The aim of this work is to elucidate the structure of some silica-supported TiO₂ photocatalysts recently developed as well as to evaluate the role that the porous structure of the support can play in the observed photocatalytic activities. In comparison with the use of an amorphous silica support, the use of the mesostructured silica SBA-15 produces an ordered structure in which TiO₂ crystals of similar sizes, independently of titania loading, are located inside the mesoporous channels of the support. The photocatalytic treatment of several cyanide-containing compounds is analyzed and the results are explained in terms of the structure of every catalyst. Depending on the model compound, the characteristic structure of the TiO₂/SBA-15 materials allows increasing up to eight times the activity achieved by the Degussa P25 TiO₂. The main conclusion of this work is the strong influence of the textural properties of the support on the catalytic activity of immobilized TiO₂ photocatalysts.     

铬、镍、铜、磷、氰现场快速检测

为了快速检测废水中的铬、镍、铜、磷、氰等有害物质,采用自制的一些化学试剂,对Cr6 、Ni2 、Cu2 、P5 、CN-在废水处理现场进行目视比色检测,速度快,能迅速判定废水中有害物质是否达到国家规定的排放标准,检测结果合格达标即可排放,省时、省费用、简捷方便、适宜工矿企业废水处理中有害元素Cr6 、Ni2 、Cu2 、P5 、CN-的快速检测.