Sorption studies of heavy metal ions on pectin-nano-titanium dioxide composite adsorbent

The Cu(II), Cd(II), Zn(II), and Pb(II) sorption kinetics and equilibrium on hybrid material, composed of pectin and titanium dioxide nanopowder, were examined. Parameters, such as pH and adsorbent dose, were also investigated. The experimental data were better described by the Langmuir model. The maximum adsorption capacities were 1.37, 0.68, 0.51, and 0.83 mmol/g for Cu(II), Cd(II), Zn(II), and Pb(II), respectively. The introduction of nano-TiO₂ improved the kinetics of the metal ion sorption. The titanium dioxide, despite its small content (6%), contributes to the removal of the examined metal ions and eventually to the adsorption capacity of hybrid beads.     

Modeling hydrogen fluoride adsorption by sodium fluoride

In the current study, hydrogen fluoride (HF) adsorption onto the sodium fluoride pellets is modeled. For this purpose a two-dimensional, non-isothermal model was developed and the governing equations were solved numerically. The contributions of diffusion transport in axial and radial directions also were considered in mathematical formulations. The model results of effluent concentration and breakthrough curves of HF were compared with the experimental data obtained in a lab-scale adsorption unit, reported in our previous work [1]. The results indicate while the feed gas velocity decreases, the HF adsorption capacity on NaF is significantly enhanced and there is a delay in breakthrough time. The adsorption capacity of HF on NaF decreases slightly when inlet HF concentration increases. Moreover, the model results were compared with the obtained results from a one-dimension model. This comparison indicates that one-dimensional model can well predict the HF dynamic adsorption behavior for lab-scale fixed beds. Comparing the experimental breakthrough curves of HF adsorption on NaF pellets with the model results shows the ability and accuracy of the model with maximum 7.82% errors.     

低温溶胶凝胶法制备尖晶石MgFe2O4纳米材料

采用新型低温溶胶凝胶法制备尖晶石结构的MgFe2O4纳米微粒。在此方法中,由于前驱体凝胶的高均匀性,使得反应温度和时间比固相法和其它化学方法极大降低。结果表明,在70℃下形成了尖晶石结构约在15~20nm之间的MgFe2O4纳米微粒。     

饮用水除氟技术研究进展

文章论述了饮用水的除氟方法,介绍了目前大规模使用的沉淀分离法,如混凝沉淀法、电凝聚法、电渗析法等,以及吸附分离法,如骨炭法、活性氧化铝法、沸石法、活性炭法、反渗透法、离子交换法等。文章阐述了各种除氟技术存在的优缺点,并对各种除氟技术的机理进行了详细的解析。此外,针对目前饮用水除氟技术,提出了几点建议。     

氟化铝生产废水处理工艺的研究

对氟化铝生产废水的处理方法进行了研究。结果表明,一级中和沉淀法和二级中和二级沉淀法均不宜用于氟化铝生产废水的结果,理想的处理方法是碱过量中和酸回调法,辅加氯化钙的石灰乳中和法也可考虑采用。     

饮用水除氟方法及其机理

综述了近年来国内外饮用水除氟方法,如石灰沉淀法、混凝沉降法、吸附与离子交换法、电凝聚法、电渗析法、反渗透法等。同时讨论了各种除氟方法的机理及进展。     

铝型材厂含氟废水的除氟工艺研究

通过实验室模拟混沉降法除氟过程,研究了铝型材工业废水除氟的达宜工艺条件。在实验条件下,氟与氢氧化钙、聚铝、FW络合助剂形成多元络合物复合盐,然后用聚丙烯酰胺絮凝,废水中氟浓度可降至4mg/L。经过两厂的工业废水现场试验,初步结果表明,排放废水含氟量达到国家标准。     

Removal of Fluoride from Aqueous Solution Using Aluminum-Impregnated Chitosan Biopolymer

Abstract

Aluminum impregnated chitosan (AIC) was prepared and applied as an adsorbent for the removal of fluoride from aqueous solutions. The process involved two stages: (i) isolation of chitosan from chitin, (ii) impregnation of aluminum in isolated chitosan at fixed pH. SEM and EDS techniques were used to characterize the composition of adsorbent AIC. Dynamic adsorption experiments on AIC were carried out at various pH, contact times, adsorption dosages, and initial fluoride concentration to determine optimum adsorption properties. The experimental data were analyzed using two adsorption models, Langmuir and Freundlich, with the later system providing the best fit. Thermodynamic parameters showed the adsorption process as spontaneous and endothermic. The adsorption process follows first-order kinetics for which a mechanism has been proposed. Reusability of the AIC was tested up to four consecutive cycles. The desorption experiment showed 92% elution of adsorbed fluoride at a pH of 12. Finally, the performance of the adsorbent material was studied on field water samples collected from a fluorosis endemic-region.     

溶胶凝胶法制备Ni掺杂AZO纳米粉体及其表征

利用溶胶凝胶法制备Ni掺杂AZO(NAZO)纳米粉体。通过TG-DSC、XRD、TEM、XPS等分析手段,研究掺杂浓度和煅烧温度对纳米粉体结构和电学性能影响规律。结果表明:在600℃下煅烧2 h,NAZO纳米粉体具有六角纤锌矿结构,粉体的粒径约25~35 nm,主要呈现球状和棒状结构。当铝掺杂摩尔百分比为1 mol%,镍掺杂摩尔百分比为1.5 mol%时,纳米粉体的电阻率为4.309 M?·cm。     

碳酸钙和氧化钙脱除煤气中H2S和COS的研究

采用热重分析法在常压下对CaCO3和CaO分别脱除H2S和COS的反应进行了研究。结果表明,脱除H2S和COS的反应初速率分别与H2S分压和COS分压成正比;CaO脱除H2S和COS的反应速度与颗粒粒度成反比,与颗粒的比表面积成正比例。与CaO脱除H2S和COS的反应相比,CaCO3脱除H2S和COS反应的初速率慢得多。     

改性活性氧化铝除氟性能研究

通过静态实验,研究了改性活性氧化铝(MAA)对F-的吸附性能,考察了吸附时间、改性活性氧化铝的用量对除氟性能的影响,并与新型除氟树脂的除氟性能进行了比较.研究结果表明:活性氧化铝的用量为4 g时,除氟效率最高,为94.57%;活性氧化铝与含氟水的最佳接触时间为3 h;MAA在较低用量(＜4 g)时,除氟效率不如除氟树脂高,但是在较高用量(≥4 g)下,MAA则高于树脂的除氟效率.     

石灰石和氧化钙脱除H2S和COS动力学研究

向煤气化炉中喷入石灰石或氧化钙粉是脱除煤气中含硫化合物最简便的方法之一。文中采用热重分析仪在常压(绝压为0.1 MPa)下对石灰石和氧化钙分别脱除H2S和COS的反应进行了动力学研究。实验条件为:温度1 025—1 450 K、H2S和COS的分压范围0.000 3—0.001 5 MPa、颗粒粒径为0.84—1.0 mm。结果表明,石灰石和氧化钙与H2S和COS的反应均表现为一级反应;与CaCO脱除H2S和COS的反应相比,CaO3脱除H2S和COS反应的初速率几乎快10倍。在0.105—1.0 mm粒径范围内的实验表明,CaO脱除H2S和COS的反应与颗粒粒度成反比关系。     

饮用水沸石除氟的实验研究

本文通过静态搅拌实验和恒温震荡实验研究了接触时间、pH值、温度对沸石除氟效果的影响 ;测定了在 2 5℃时沸石除氟的吸附等温线 ,并对吸附等温线进行拟合 ,证明其符合Langmuir吸附等温式qe=0 .0 68Ce/(1 0 .0 868Ce) ;对吸附速度进行了数学处理 ,证明其符合斑厄姆吸附速度公式dq/dt=0 .0 0 1 8(qe-q) /t0 .2 2 。     

Potential of Sawdust for the Decontamination of Lead from Aqueous Media

Abstract

The sorption of lead ions on sawdust has been exploited to evaluate its potential for the decontamination of lead ions from aqueous solutions. Various physico‐chemical parameters such as selection of appropriate electrolyte, equilibration time, amount of adsorbent, concentration of adsorbate, effect of diverse ions and temperature were studied in order to simulate the best conditions in which this material can be used as an adsorbent. Maximum adsorption was observed at 0.005 mol · L^?1 acid solutions (HNO₃, HCl, and HClO₄) using 0.2 g of adsorbent for 4.83×10^?5 mol · L^?1 lead concentration in 10 min equilibration time. Studies show that the adsorption of lead decreases with the increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the lead concentration range of 2.41×10^?5 to 4.83×10^?4 mol · L^?1. The characteristic Freundlich constants, i.e., 1/n=0.49±0.02 and K=0.142±0.0038 m · mol · g^?1 have been computed for the sorption system. The sorption mean free energy from the Dubinin‐Radushkevich isotherm is 11.26±0.31 kJ mol^?1 indicating ion‐exchange mechanism of chemisorption. The uptake of lead decreases with the rise in temperature (293–323 K). Thermodynamic quantities, i.e., ΔG, ΔS, and ΔH have also been calculated for the system. The sorption process was found to be exothermic. The proposed procedure was applied for the removal of lead from battery water samples.