Extraction and separation of Fe(Ⅲ) from heavy metal wastewater using P204 solvent impregnated resin

The extraction and separation of Fe（III） from heavy metal wastewater generated in zinc smelting process were studied using solvent impregnated resin containing CL- P2O4. The influence of pH and temperature on absorbing heavy metal cations by static adsorption was investigated. The batch tests on adsorption equilibrium, kinetics and elution efficiency were carried out to evaluate the performance of CL-P204. Column operations for extraction and separation of Fe（III） by CL-P2O4 were performed for further optimization of process parameters and feasibility evaluation. The reaction mechanism of Fe（III） and CL-P2O4 was analyzed through saturation capability, slope analysis and infrared spectroscopy （IR）. The results show that the separation of Fe（III） from heavy metal wastewater using CL- P2O4 can be achieved through process of adsorption and desorption at a flow rate of 1.53 ml·min^-1·cm^-2, pH 0.8 and temperature of 25℃. The experimental data of Fe（III） adsorption by CL-P2O4 have a satisfactory fit with Langmuir adsorption equation and Freundlich adsorption isotherms. The probable molecular formula of extracted complex is Fe[R2（R2H）], and the adsorption reaction equation is concluded as following： Fe3＋ ＋ 4RH 〈=〉Kex Fe[R2（R2H）] ＋ 3H＋ （Kex, extraction equilibrium constant）. This study will supply the fundamentals for treatment of heavy metal wastewater.

Study and Solutions to the Issue of Heavy Metals from Wet FGD Wastewater

The conventional wet FGD process has been applied in more than 85% units for SO2 removal in China. There are a great number of pollution components in the wastewater from wet FGD process,and the removal process of these components is very complicated and difficult,especially the removal of heavy metals in the wastewater. Even if a foreign advanced technology was applied,it is still difficult to meet the discharge requirements of heavy metals in spite of its much higher investment,operation and maintenance cost than that from the domestic widely-used and simple wastewater treatment process. Under the background of increasingly stringent environmental requirements,to improve the existing wastewater treatment process or to change the existing wet FGD process has become extremely urgent.

Two-sectional struvite formation process for enhanced treatment of copper-ammonia complex wastewater

Mg2＋ and PO43＋ were added into the synthetic wastewater, leading to the dissociation of the complex ions in the wastewater, and resulting in removal of copper and ammonia therein. The effects of agents addition amount, pH, and reaction time on the removal efficiency of copper and ammonia were investigated. In particular, two-sectional struvite formation （TSSF） process was established for copper and ammonia removal. MgCl2 and Na2HPO4 were added by following 90% addition in the first section and remained 10% in the second during the TSSF process. Compared with one sectional struvite formation, TSSF possessed much better performance. Under condition of n（NH3-N）：n（Mg）：n（P）=1：1.2：1.5 （molar ratio）, pH=9, and reaction time of 30 min, the removal efficiencies of copper and ammonia were 98.9% and 99.96%, respectively. The enhanced performance of TSSF is explained by the competition of ammonia by copper？ammonia complexes and struvite. The dissociation of copper-ammonia complexes is further demonstrated by thermodynamic equilibrium analysis, on the basis of calculations and establishment of predominance phases diagram. Moreover, XRD and EDS analyses further confirmed the formation of struvite and precipitation of copper, which prove the transmission of copper and ammonia from liquid phase into solid phase.

Adsorption of copper ions on porous ceramsite prepared by diatomite and tungsten residue

In order to realize resource utilization of industrial tungsten residue and treatment of heavy metal wastewater in mining and metallurgical area of south China,a novel ceramsite was prepared with the main raw materials of diatomite and tungsten residue.The adsorption behavior of copper ions in solution on the ceramsite was investigated.Results indicated that the surface of the newly-developed ceramsite was rough and porous.There were lots of pores across the ceramsite from inner to outside.MnFe2O4 was one of the main components of the ceramsite.The Cu^2＋adsorption capacity by the ceramsite reached 9.421 mg/g with copper removal efficiency of 94.21%at 303 K,initial Cu^2＋concentration of 100 mg/L and dosage of 0.5 g after 300 min adsorption.With increase of ceramsite dosage,the total adsorption amount of Cu^2＋increased,but the adsorption capacity decreased.The adsorption capacity increased with the increase of solution p H.The isothermal adsorption of Cu^2＋by the ceramsite fitted the Freundlich model better.The adsorption mainly occurred on a heterogeneous surface,and was a favorable process.The adsorption process closely followed the pseudo-second kinetic equation.In initial stage of wastewater treatment,the adsorption process should be controlled mainly by diffusion,and the removal of Cu^2＋can be improved by enhancing agitation.

Construction of defect-containing UiO-66/MoSe_(2) heterojunctions with superior photocatalytic performance for wastewater treatment and mechanism insight

Metal-organic frameworks are recognized as promising multifunctional materials,especially metal-organic framework-based photocatalysts,which are considered to be ideal photocatalytic materials.Herein,a new type of UiO-66/MoSe_(2) composite was prepared using the solvothermal method.The optimum composite was selected by adjusting the mass ratio of UiO-66 and MoSe_(2).X-ray diffraction analysis showed that the mass ratio influenced the crystal plane exposure rate of the composite,which may have affected its photocatalytic performance.The composite is composed of ultra-thin flower-like MoSe_(2) that wrapped around cubic UiO-66,a structure that increases the abundance of active sites for reactions and is more conducive to the separation of carriers.The photocatalytic properties of the composite were evaluated by measuring the degradation rate of Rhodamine B and the catalyst’s ability to reduce Cr(VI)-containing wastewater under visible light irradiation.Rhodamine B was decolorized completely in 120 min,and most of the Cr(VI)was reduced within 150 min.The photochemical mechanism of the complex was studied in detail.The existence of Mo^(6+)and oxygen vacancies,in addition to the Z-type heterojunction promote the separation of electrons and holes,which enhances the photocatalytic effect.

Low-temperature conversion of ammonia to nitrogen in water with ozone over composite metal oxide catalyst

As one of the most important water pollutants, ammonia nitrogen emissions have increased year by year, which has attracted people＇s attention. Catalytic ozonation technology, which involves production of ·OH radical with strong oxidation ability, is widely used in the treatment of organic-containing wastewater. In this work, MgO-Co3O4 composite metal oxide catalysts prepared with different fabrication conditions have been systematically evaluated and compared in the catalytic ozonation of ammonia（50 mg/L） in water. In terms of high catalytic activity in ammonia decomposition and high selectivity for gaseous nitrogen, the catalyst with MgO-Co3O4 molar ratio 8：2, calcined at 500°C for 3 hr, was the best one among the catalysts we tested, with an ammonia nitrogen removal rate of 85.2% and gaseous nitrogen selectivity of44.8%. In addition, the reaction mechanism of ozonation oxidative decomposition of ammonia nitrogen in water with the metal oxide catalysts was discussed. Moreover, the effect of coexisting anions on the degradation of ammonia was studied, finding that SO2-4 and HCO-3 could inhibit the catalytic activity while CO2-3 and Br-could promote it. The presence of coexisting cations had very little effect on the catalytic ozonation of ammonia nitrogen. After five successive reuses, the catalyst remained stable in the catalytic ozonation of ammonia.

Rapid adsorption of toxic Pb(Ⅱ) ions from aqueous solution using multiwall carbon nanotubes synthesized by microwave chemical vapor deposition technique

Multiwall carbon nanotubes（MWCNTs） were synthesized using a tubular microwave chemical vapor deposition technique, using acetylene and hydrogen as the precursor gases and ferrocene as catalyst. The novel MWCNT samples were tested for their performance in terms of Pb（Ⅱ）binding. The synthesized MWCNT samples were characterized using Fourier Transform Infrared（FT-IR）, Brunauer, Emmett and Teller（BET）, Field Emission Scanning Electron Microscopy（FESEM） analysis, and the adsorption of Pb（Ⅱ） was studied as a function of p H,initial Pb（Ⅱ） concentration, MWCNT dosage, agitation speed, and adsorption time, and process parameters were optimized. The adsorption data followed both Freundlich and Langmuir isotherms. On the basis of the Langmuir model, Qmaxwas calculated to be 104.2 mg/g for the microwave-synthesized MWCNTs. In order to investigate the dynamic behavior of MWCNTs as an adsorbent, the kinetic data were modeled using pseudo first-order and pseudo second-order equations. Different thermodynamic parameters, viz., ΔH0, ΔS0and ΔG0were evaluated and it was found that the adsorption was feasible, spontaneous and endothermic in nature. The statistical analysis revealed that the optimum conditions for the highest removal（99.9%） of Pb（Ⅱ） are at p H 5, MWCNT dosage 0.1 g, agitation speed 160 r/min and time of 22.5 min with the initial concentration of 10 mg/L. Our results proved that microwave-synthesized MWCNTs can be used as an effective Pb（Ⅱ） adsorbent due to their high adsorption capacity as well as the short adsorption time needed to achieve equilibrium.