由高铁低锌萃铟废水制备锌精矿和铁红

控制pH值,对高铁低锌萃铟废水加入硫精矿直接制备锌精矿和铁红进行了研究. 分析了反应机理,考察了不同硫化物对锌的回收效果,探讨了超声波辅助硫精矿制备锌精矿和高纯铁红的工艺条件,并利用SEM对锌精矿粒度和形貌进行表征. 在萃铟废水中含铁60.47 g/L、锌28.65 g/L时,在常温下调节pH值为2,加入-0.074 mm硫精矿,超声处理50 min的实验条件下,制得了含锌50.36%的锌精矿产品,锌回收率达95.29%,锌含量和回收率分别比未经超声处理提高了18.52%和23.67%. 制得的高纯铁红符合国家SJ/T10383-93标准一等品的要求,铁回收率为92%.     

Combined Adsorption and Ultrafiltration Processes Employed for the Removal of Pollutants from Metal Plating Wastewater

This work investigated the use of combined sorption and ultrafiltration (UF) processes for the treatment of electroplating wastewater. The combined vermiculite – UF and bentonite – UF treatment schemes were assessed for their ability to remove nickel, zinc, organic, matter, and color. UF significantly reduced nickel and zinc concentration from wastewater at alkaline environment with removal efficiencies higher than 89% at pH ≥ 8 for both metals. Mineral addition increased metal removal efficiency to higher values (> 97% at pH ≥ 8). The presence of organic compounds and cations in wastewater limited the adsorption efficiency of minerals. Binary metal solutions suppressed the adsorption process for both nickel and zinc. The adsorption of metals on minerals was a multi-stage process where intraparticle diffusion was not the only rate limiting step. Isotherm examination showed that the best fit to the experimental data was obtained by the Langmuir model, and the three parameter models of Redlich-Peterson, Toth, and Sips converged to the Langmuir model. UF combined with minerals resulted in significant removal of organics and color. Furthermore, UF of wastewater resulted in limited membrane fouling.     

3D Hierarchical Porous and N-Doped Carbonized Microspheres Derived from Chitin for Remarkable Adsorption of Congo Red in Aqueous Solution

A novel adsorbent of N-doped carbonized microspheres were developed from chitin (N-doped CM-chitin) for adsorption of Congo red (CR). The N-doped CM-chitin showed spherical shape and consisted of carbon nanofibers with 3D hierarchical architecture. There were many micro/nano-pores existing in N-doped CM-chitin with high surface area (455.703 m² g⁻¹). The N element was uniformly distributed on the carbon nanofibers and formed with oxidize-N graphitic-N, pyrrolic-N, and pyridinic-N. The N-doped CM-chitin showed excellent adsorption capability for CR and the maximum adsorption amount was approximate 954.47 mg g⁻¹. The π-π/n-π interaction, hydrogen-bond interactions, and pore filling adsorption might be the adsorption mechanisms. The adsorption of N-doped CM-chitin was considered as a spontaneous endothermic adsorption process, and which well conformed to the pseudo-second-order kinetic and Langmuir isotherm model. The N-doped CM-chitin exhibited an effective adsorption performance for dynamic CR water with good reusability. Therefore, this work provides new insights into the fabrication of a novel N-doped adsorbent from low-cost and waste biomasses.     

Fabrication, Characterization and Application of Polymer Nanocomposites for Arsenic(III) Removal from Water

Polymer nanocomposites constituted of [ethylene-vinyl acetate (EVA) (70 %) polycaprolactone (PCL) (15 %) Fe₃O₄ (15 %)] were synthesized and applied in the removal of Arsenic(III) from contaminated water. Arsenic contamination in water is a severe problem globally because arsenic is toxic even at low concentrations. The aim of this study is to incorporate magnetite (Fe₃O₄) into a polymer blend that is to be used as an adsorbent for the removal of As(III). In this study EVA–PCL copolymers with magnetite were synthesized via the melt blending technique. The nanocomposites were characterized by the use scanning electron microscopy, thermogravimetry analysis and X-ray diffraction. Batch experiments were carried out to investigate the ability of polymer nanocomposites to adsorb As(III) from contaminated water. A maximum sorption capacity of 2.83 mg/g at 26 ± 2 °C and pH 8.6 was obtained. Adsorption data were fitted to Langmuir, Freundlich and Dubinin–Radushkevich isotherms. The process fits well with the Langmuir isotherm. As(III) obeyed pseudo-second order kinetics. The nanocomposites investigated in this study showed good potential for As(III) removal from contaminated water. The dispersion of magnetite nanoparticles into the polymers resulted with improved surface area for better adsorption of As(III).     

Evaluation of the Efficiency of a Combined Adsorption–Ultrafiltration System for the Removal of Heavy Metals,Color, and Organic Matter from Textile Wastewater

In this work an ultrafiltration (UF) membrane system was investigated for the treatment of textile wastewater. UF membranes were assisted by activated sludge and minerals, which were employed as sorbents, to remove Cu(II), Pb(II), Zn(II), Ni(II), color, and organics. Significant variations were observed in metal removal efficiencies among the textile wastewater samples of different origin, even at the same pH (= 6) due to the presence of different compounds in wastewater. At the examined pH range (5.63–9.21), the dominant mechanism for copper and lead removal was the formation of insoluble metals due to precipitation and complexation of metal ions with wastewater compounds, including adsorption of metals on suspended solids and colloidal matter. The adsorption process of metals on minerals and activated sludge was the dominant process for nickel and zinc removal at low pH, while precipitation/complexation prevailed at higher pH. The examined adsorption-UF system could produce a treated effluent having low metal concentrations that could be safely discharged into municipal sewers. COD removal ranged from 76%–92% for the five textile wastewater samples. The color removal accomplished was significant (45%–70%), and depended on the type of dye.     

Adsorption capacity of bone char for removing fluoride from water solution. Role of hydroxyapatite content,adsorption mechanism and competing anions

The adsorption of fluoride from water on bone char (BC) was investigated in this work, and the fluoride adsorption capacity of BC was compared to that of hydroxyapatite (HAP). The adsorption capacity of BC and HAP drastically increased while decreasing the pH from 7.0 to 5.0. Furthermore, the fluoride adsorption on BC was due to its HAP content and was not considerably affected by the presence of the anions Cl⁻, HCO₃⁻, CO₃²⁻, SO₄²⁻, NO₃⁻ and NO₂⁻. The mechanism of fluoride adsorption on BC was attributed to electrostatic interactions between surface charge of BC and fluoride ions in solution.     

Application of Full Factorial Design for Removal of Polycyclic Aromatic Dye from Aqueous Solution Using 4A Zeolite: Adsorption Isotherms,Thermodynamic and Kinetic Studies

In this study, removal of the cationic dye acridine orange (AO) from aqueous solution using 4A zeolite was studied. The adsorption experiments were performed using batch system, and full factorial design was employed for investigating the condition of removal efficiency of dye. The four most important operating variables were the initial pH of the solution, the concentration of dye, the contact time, and the temperature. The 18 experiments were required to investigate the effect of variables on removal of the dye. The results were statistically analyzed to define important experimental variables and their levels using the analysis of variance (ANOVA). A regression model that considers the significant main and interaction effects was suggested and fitted the experimental data very well. Model predictions were found to be in good agreement (R² = 99.99%, adjusted R² = 99.86%) with experimental data. The optimized conditions for dye removal were at initial pH 3.0, 20.0 mg L^?1 dye, temperature 298.0 K and 80.0 min adsorption time. The experimental data were analyzed by the Langmuir, Freundlich, Temkin and Sips adsorption models. The maximum predicted adsorption capacities for AO was obtained as 29.851 mg g^?1. The adsorption thermodynamic parameters, namely ΔH°_ads, ΔG°_ads and ΔS°_ads, were determined. Furthermore, the kinetic of AO adsorption on the 4A zeolite was analyzed using pseudo-first- and second-order kinetic models and the results showed that the removal was mainly a pseudo-second-order process.     

Synthesis of Extraction Resin Containing N,N,N′,N′-Tetraisobutyl Diglycolamide and its Application for Separation of Sr(II) from Rb(I)

Abstract

A novel Levextrel resin containing N,N,N′,N′-tetraisobutyl diglycolamide (TiBDGA) was synthesized by suspension polymerization of styrene and divinylbenzene and its performance for separation of Sr(II) from Rb(I) was investigated. The effects of crosslink degree, stirring speed, and the ratio of porogenic-agents on the resin synthesized were examined. The optimum TiBDGA resin with 40 wt.% divinylbenzene as cross linking agent and 20 wt.% of n-octanol as porogenic-agents provided excellent adsorption capacity of 22.5 mg/g. The distribution coefficient (K _d) of Sr(II) in HNO₃ media onto the resin depended heavily on the acidity in the aqueous solution. The maximum K _d for Sr(II) (7300 mL/g) was observed when the HNO₃ concentration in aqueous phase reached 2 mol/L. The difference in the Sr(II) and Rb(I) distribution coefficients of several orders of magnitude implied that ⁸⁹Sr may be separated from ⁸⁶Rb with a radionuclide purity greater than 99%. And the maximum static adsorption capacity of Sr(II) on the resin was 22.5 mg/g.