Effects of fluoride on the removal of cadmium and phosphate by aluminum coagulation

This study focuses on the effects of pH and fluoride at different molar ratios of fluoride to Al (R_F:Al) on the removal of cadmium (Cd²⁺) and phosphate by Al coagulation. Fluoride at R_F:Al ≥ 3:1 inhibits the removal of Cd over wide Al dose ranges from 5 to 10 mg/L as Al. The removal of phosphate decreases significantly at high R_F:Al of 10:1 whereas at lowered R_F:Al (i.e., ≤ 6:1), an adverse effect is observed only at insufficient Al doses below 2 mg/L. Fluoride shows inhibitive effects towards the removal of Cd at pH 7 and 8 and that of phosphate at pH 6. Fluoride decreases the ζ-potential in both systems, and the decreasing extent is positively correlated to the elevated R_F:Al. The Al fluoride interactions include the formation of Al–F complexes and the adsorption of fluoride onto Al(OH)₃ precipitates, i.e., the formation of Al(OH)_nF_m. Al–F complex formation inhibits Al hydrolysis and increases residual Al levels, and a more significant increase was observed at lower pH. Al–F complexes at high R_F:Al complicate the coagulation behavior of Al towards both negative and positive ionic species. Moreover, fluoride at low R_F:Al shows little effect on Al coagulation behavior towards Cd^2 + and phosphate, and the spent defluoridation adsorbent, i.e., aluminum (Al) hydro(oxide) with adsorbed fluoride at R_F:Al of below 0.1:1, may be reclaimed as a coagulant after being dissolved.     

硫酸铁与聚合氯化铝处理城市景观水的比较实验研究

针对城市景观水的水质状况加剧恶化,本文对比在不同情况下用氯化铁及聚合氯化铝处理景观水,探讨了投加量、搅拌速度、搅拌时间、静沉时间以及pH对景观水有机物和浊度去除率的影响.结果表明:当水样pH值在6～8之间时,投加4～6mL混凝剂后,当先中速搅拌(120 r/min)2 min,最后慢速搅拌(60 r/min)搅拌10 min.此后静沉35 min,此时CODcr去除率及浊度去除率都可达到最佳情况;其中pH为8时,硫酸铁对CODcr去除率可达82％,浊度去除率率为92％;当PH为7时PAC对城市景观水CODcr的去除可达84％,浊度去除率率为96％.聚合氯化铝的处理效果优于硫酸铁,故而得出处理城市景观水时更适合选用聚合氯化铝.     

Antimony(V) removal from water by hydrated ferric oxides supported by calcite sand and polymeric anion exchanger

We fabricated and characterized two hybrid adsorbents originated from hydrated ferric oxides(HFOs) using a polymeric anion exchanger D201 and calcite as host. The resultant adsorbents(denoted as HFO-201 and IOCCS) were employed for Sb(V) removal from water. Increasing solution pH from 3 to 9 apparently weakened Sb(V) removal by both composites, while increasing temperature from 293 to 313 K only improved Sb(V) uptake by IOCCS. HFO-201 exhibited much higher capacity for Sb(V) than for IOCCS in the absence of other anions in solution. Increasing ionic strength from 0.01 to 0.1 mol/L NaNO3would result in a significant drop of the capacity of HFO-201 in the studied pH ranges; however, negligible effect was observed for IOCCS under similar conditions. Similarly, the competing chloride and sulfate pose more negative effect on Sb(V) adsorption by HFO-201 than by IOCCS, and the presence of silicate greatly decreased their adsorption simultaneously, while calcium ions were found to promote the adsorption of both adsorbents. XPS analysis further demonstrated that preferable Sb(V) adsorption by both hybrids was attributed to the inner sphere complexation of Sb(V) and HFO, and Ca(II) induced adsorption enhancement possibly resulted from the formation of HFO-Ca-Sb complexes. Column adsorption runs proved that Sb(V) in the synthetic water could be effectively removed from 30 μg/L to below 5 μg/L(the drinking water standard regulated by China), and the effective treatable volume of IOCCS was around 6 times as that of HFO-201, implying that HFO coatings onto calcite might be a more effective approach than immobilization inside D201.     

电化学间接氧化法处理H_2S气体的研究

采用填料塔对铁盐溶液吸收 H2 S的过程进行了初步研究 ,考察了气液比、填料层高度、吸收温度、Fe3+浓度、进气 H2 S浓度和 H+浓度等因素对 H2 S去除率的影响。结果表明 ,气液比、填料层高度和吸收温度对吸收效率的影响比较显著。通过正交试验选出最佳工艺条件 ,在此工艺条件下 H2 S的去除率接近 10 0 %。     

用铁泥制氧化铁红

研究了以染化厂废料铁泥和工业废硫酸为原料,采用高温干法制取氧化铁红的工艺,简要介绍了该法生产氧化铁红的反应机理,探讨了氧化剂,氧化时间,氧化温度等对产品质量的影响,确定了适宜工艺条件,提出了工业生产流程和尾气治理方案。     

Biodegradation of Low Molecular Weight Organic Acids in a Limed Forest Soil

The effect of liming (3.45 and 8.75 t ha^-1 dolomite; 16 yr after application) on the biodegradation of three low molecular weight organic acids (citrate, oxalate and propionate) in forest soils was investigated. The concentration of organic acids in the soil solution followed the series propionate > citrate > oxalate with liming having no significant impact on soil solution concentrations (mean organic acid concentration = 8.7 ± 2.3 M). Organic acid mineralization by the soil microbial community was rapid in surface organic horizons (mean half-life for citrate = 2–6 h), with biodegradation rate gradually declining with soil depth. Concentration-dependent biodegradation studies (0 to 350 M) showed that the mineralization kinetics generally conformed well to a single Michaelis–Menten equation with V_max values following the series oxalate > citrate > propionate (mean = 9.8 ± 1.0 nmol g^-1 h^-1) and K_M values following the series oxalate = citrate > propionate (mean 168 ± 25 M). The V_max values declined with soil depth, which was consistent with a general reduction in microbial activity down the soil profile. Liming induced a significant increase in V_max for citrate with no change for propionate and reduction in V_max for oxalate. The latter was probably due to adsorption and precipitation of Ca-oxalate making it unavailable for microbial uptake. The higher adsorption/precipitation capacity for oxalate in the limed soils was confirmed by adsorption isotherms. Generally, liming increased soil microbial activity by approximately 10 to 35% with calculations based on soil solution concentrations indicating that organic acid mineralization constituted approximately 3 to 15% of the total soil respiration.     

复合絮凝剂聚硅酸铝铁的形貌结构及性能研究

向聚硅酸中引入铝盐、铁盐制得聚硅酸铝铁(PFAS)复合絮凝剂,用电子显微镜观察分析了不同Al/Fe/Si摩尔比的PFAS形貌,用红外光谱研究了其中铝离子、铁离子与聚硅酸的相互作用情况,并对其絮凝性能进行了考察.结果发现:聚硅酸铝铁的形貌均为枝杈状聚集态,并带有分形特征,完全不同于聚硅酸的球形或椭球形,也不同于聚铝、聚合铝铁的晶形;Al/Fe/Si摩尔比对形貌有较大影响.红外光谱证实了PFAS中部分铝离子、铁离子及水解络合铝离子、铁离子可与共存的聚硅酸起螯合(络合)反应生成铁铝硅聚合物,PFAS的絮凝性能高于聚硅酸铝、聚硅酸铁.     

再生造纸废水絮凝除浊试验研究

本研究采用絮凝法对再生造纸废水中含细小纤维、无机填料的悬浮物进行处理试验，比较了硫酸亚铁与聚丙烯酰胺复合絮凝剂和聚硅酸氯化铁盐两种絮凝剂的絮凝效果，研究了制备聚硅酸氯化铁盐的铁硅比、pH值、碱化度以及投加量与废水除浊率之间的相互关系。实验结果表明：在最佳条件下，絮凝效果优异，除浊率达到98％，上清液无色透明。     

Preliminary Studies on Converting Agricultural Waste into Biodegradable Plastics,Part I: Corn Distillers’ Dry Grain

Distillers dry grain (DDG) was derivatized either by carboxymethylation, glutaration, maleiation, phthallation, or succination in order to produce anionic materials suitable for complexation with soy protein isolate. Infrared spectroscopy confirmed that derivatization of DDG by all reagents was successful. Blending of derivatized anionic products with soy protein resulted in instant precipitation of gels. The gels were centrifuged, molded, and dried into solid pellets with tensile strengths as high as 1.67MPa, suggesting that these materials could be promising as biodegradable structural materials. Infrared spectroscopy suggested the possibility of complexes forming between soy protein isolate and each of the derivatized DDG samples.     

UV/草酸铁络合物光解对硫磷的研究

研究了紫外光（UV）/草酸铁络合物对对硫磷的光解作用,结果表明,UV/草酸铁络合物能快速有效地光解对硫磷,且较UV/TiO2的光解效果好。对硫磷光解率随着其初始浓度的增加而降低;pH为3-5时其光解速率最快;[Fe(Ⅲ）]与[OX^2-]之比（OX^2-代表草酸根）和溶液中的溶解氧对其光解有显著影响。