A functionalized activated carbon adsorbent prepared from waste amidoxime resin by modifying with H_(3)PO_(4) and ZnCl_(2) and its excellent Cr(Ⅵ)adsorption

With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(Ⅵ) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(Ⅵ). The waste amidoxime resin was first modified with H3PO4 and ZnCl_(2), and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(Ⅵ) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(Ⅵ) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(Ⅵ) to Cr(Ⅲ) and decrease the toxicity of Cr(Ⅵ) during adsorption. PPR-Z exhibited Cr(Ⅵ) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(Ⅵ) adsorption are the chemical reduction of Cr(Ⅵ) into Cr(Ⅲ) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(Ⅵ) pollution and realizes the concept of “treating waste with waste”.

Synergism of solar-driven interfacial evaporation and photo-Fenton Cr(Ⅵ) reduction by sustainable Bi-MOF-based evaporator from waste polyester

The integration of interfacial solar steam generation and photocatalytic degradation technology has pro-vided a promising platform to simultaneously produce freshwater and degrade pollutants.However,con-structing low-cost,multi-functional evaporators for treating Cr(Ⅵ)-polluted water remains challenging,and the synergistic mechanism on Cr(Ⅵ)reduction is fuzzy.Herein,we propose the combined strategy of ball milling and solution mixing for the sustainable production of Bi-MOF microrod from waste poly(ethylene terephthalate),and construct Bi-MOF-based solar evaporators for simultaneous photo-Fenton Cr(Ⅵ)reduction and freshwater production.Firstly,the evaporator comprised of Bi-MOF microrod and graphene nanosheet possesses high light absorption,efficient photothermal conversion,and good hydro-philic property.Attributing to the advantages,the hybrid evaporator exhibits the evaporation rate of 2.16 kg m^(-2) h^(-1) and evaporation efficiency of 87.5%under 1 kW m^(-2) of irradiation.When integrating with photo-Fenton reaction,the Cr(Ⅵ)reduction efficiency is 91.3%,along with the reaction kinetics of 0.0548 min^(-1),surpassing many advanced catalysts.In the outdoor freshwater production and Cr(Ⅵ)reduction,the daily accumulative water yield is 5.17 kg m^(-2) h^(-1),and the Cr(Ⅵ)reduction efficiency is 99.9%.Furthermore,we prove that the localization effect derived from the interfacial solar-driven evap-oration enhances H_(2)O_(2) activation for the photo-Fenton reduction of Cr(Ⅵ).Based on the result of density functional theory,Bi-MOF microrod provides rich active centers for H_(2)O_(2) activation to produce active sites such as e-or-O_(2).This study not only proposes a new strategy to construct multi-functional solar evaporators for freshwater production and catalytic reduction of pollutants,but also advances the chem-ical upcycling of waste polyesters.

Preparation of chitosan modified fly ash under acid condition and its adsorption mechanism for Cr(VI)in water

Chitosan-coated fly ash(CWF)was prepared by the acid leaching-coating method.Chitosan and fly ash were crosslinked in the solution of acetic acid and sulfuric acid.The microstructure of CWF was conducted by scanning electron microscope(SEM)and X-ray diffraction(XRD).The removal of Cr(VI)from water by CWF was studied by adsorption experiments.The composite prepared by the experiment developed a pore structure and a crystal structure similar to SiO_(2) and chitosan chain-like coating was formed on the surface of fly ash.The new modified material has larger surface roughness,specific surface area and more adsorption channels.The Cr(VI)was enriched in modified materials by electrostatic adsorption between CrO_(4)^(2−)、CrO_(7)^(2−)and-NH_(3)^(+) group and surface acid functional groups.The movement of Cr(VI)in solution is a diffusion process from the main body of the liquid phase to the surface of the liquid film.

Evaluation of the Cr(VI) and other toxic element contamination and their potential sources:The case of the Thiva basin(Greece)

An integrated approach was performed on the soil, plant-crops and groundwater system at the Thiva basin, to evaluate the extent and intensity of the heavy metal contamination, the percentage of metals transferred into plants/crops （bio-accumulation） and the potential sources of contamination. Heavy metal contents （230--310 Cr, 1200--2200 Ni, 50--80 Co, 880--1150 Mn and 44,500--66,200 Fe all in ppm ） in the Thiva soils are higher than those in the Assopos basin. An increasing trend in the heavy metal contents, from the Assopos to the Thiva basin （Mouriki）, indicates that the metal source is probably the Ni-laterites and ophiolites, located towards north. On the other hand, groundwater samples from domestic and irrigation wells throughout the Thiva basin exhibit relatively low （8--37 ppb） concentrations in Cr compared to the Assopos （up to 150 ppb）. The plots of Cr versus Mg/Ca, Mg/Na versus Ca/Na, B versus Si/（Si ＋ Na） and Mg/Si versus Ca/Si ratios revealed a low degree of salinization in the Thiva compared to that in the Assopos （Avlida） basin. The low Cr concentration （average 23 ppb, during dry period） in the Thiva wells may be related with their depth （〉120 m）, in contrast to shallow wells in the central Euboea （hundreds ppb Cr） and points to a solution of a crucial environmental problem in Euboea and Assopos basin by using the deep karst-type aquifer instead the shallow-Neogene one. The average Cr contents （dry weight） ranges from 1.7 to 4.6 ppm （average 2.2） in carrots, potatoes and onions. The percentage of soil metals Crto^i, Cr（Vl）, Ni, Mn and Fe ranges between 0.06 and 3.2 （average （/.53 ~ 0.4）, whilst that for Cu and Zn ranges from 16 to 81 （average 36 ~ 24）. The Cr transfer to plants is low, due to the high resistance of chromite （main host of Cr）, but the determined Cr contents in plant- crops in the Thiva basin are higher than normal or sufficient vahles. Although mininml uptake for growth and production for Cr, Ni, Zn and Cn is still lacking, fnrthermorc research is required in order to restrict heavy metal accumulation and enstlre sustainability.

Removal of Chromium(VI) from Aqueous Solution Using Persimmon Tannin Gel and Subsequent Recovery as Chromium(III)

This study herein was investigated the removal of chromium(VI) from an aqueous solution using persimmon tannin gel and its subsequent recovery as chromium(III). At pH 2, Cr(VI) was effectively adsorbed (~80% adsorption) and ppm solution was reduced to Cr(III) on the persimmon gel within 10 min. Although desorption of the Cr(III) species was challenging at 30°, it was increased upon increasing the temperature and was quantitatively desorbed in the presence of 1 M hydrochloric acid under reflux. In addition, although the quantity of retained Cr(VI) on the tannin gel increased upon increasing the chromium concentration of the original aqueous solution, all the desorbed chromium was successfully reduced to Cr(III). Finally, Cr(VI) removal and recovery as Cr(III) was repeated effectively 8 times using the same persimmon tannin gel sample, thus demonstrating the recyclability of this system.

水体系As(III)和Cr(VI)氧化还原共转化技术研究进展

本文对六种应用于水体系As(III)和Cr(VI)氧化还原共转化技术的国内外研究进展进行了综述,并简要阐述了各个技术的处理方法和反应机理,以期为后续的相关研究提供借鉴和启发。

Effect of shaking time, ionic strength, temperature and pH value on desorption of Cr(III) adsorbed onto GMZ bentonite

The Cr（III） desorption experiments of Gaomiaozi （GMZ） bentonite in aqueous solutions were performed. The variables affecting the desorption behaviors, such as contact time, concentration of the desorbent, pH value of the solution, temperature and desorption isotherms, were investigated by the batch experiments. The results show that the adsorbed Cr（III） on GMZ bentonite can be easily extracted by the desorbent. Kinetics examination shows that desorption is slower than adsorption, and the desorption rate increases with time and reaches the equilibrium after 3 h. The final desorption ratios of Cr（III） are 89.4%, 56.5%and 77.2%in the desorption solution with 0.1 mol/L HCl, 1 mol/L NaCl, and 1 mol/L CaCl2, respectively, and the concentration can promote the desorption progress. Furthermore, the results of successive regeneration cycles indicate that the bentonite has a good regeneration ability and reusability. The pH value is an important factor in the Cr（III） desorption from the GMZ bentonite. The results of adsorption and desorption isotherms show that both adsorption and desorption isotherms are consistent with the Freundlich equation. The comparison of adsorption and desorption isotherms implies that the adsorption/desorption hysteresis is negligible and the transport of Cr（III） in bentonite can be described by a reversible adsorption process.

海藻酸钠基凝胶吸附材料对Cr(VI)吸附性能研究

海藻酸钠(SA)是一种天然生物质材料,其来源广、价格低,聚乙烯亚胺是一种含有氨基(-NH_(2))的水溶性高分子聚合物,螯合重金属离子能力强,众多研究者将二者结合其制备成吸附剂去除水溶液中的金属离子。本研究以海藻酸钠为基体,加入碳酸钙和聚乙烯亚胺,以戊二醛为交联剂,经冷冻干燥后形成吸附较好的海藻酸钠-聚乙烯亚胺吸附材料。采用吸附实验研究了材料对水中Cr(VI)的吸附性能,并研究初始浓度、溶液pH、吸附时间、吸附剂用量等对吸附效果的影响。实验结果表明:在Cr(VI)溶液初始浓度为15 mg/L、吸附剂用量0.4 g、吸附时间200 min,吸附温度为313 K时,Cr(VI)去除率达90%以上。

电纺丝制备磁性单晶BiFeO_(3)纳米纤维并用于Cr(VI)的可见光催化还原

本工作提出一种将溶胶凝胶与静电纺丝结合的分步快速烧结技术,成功制备了单晶BiFeO_(3)纳米纤维。通过热重差热分析(TG-DTG)、XRD、SEM、TEM、EDS、紫外可见漫反射光谱和氮气吸附脱附曲线等测试对所制备材料的结构和形貌进行表征。同时,考察了BiFeO_(3)纳米纤维在可见光下对水中Cr(VI)的光催化还原性能。结果显示,相比于传统方式制备的纳米颗粒,该材料因更大的比表面积而具有更高的光催化活性。空穴消耗剂酒石酸的加入能够促进该材料对Cr(VI)的光催化还原反应,使还原效率提高87%。总之,本文制备的BiFeO_(3)材料能在可见光下响应,并在常温下具有弱磁性,能通过磁场力回收,在环境净化领域具有广阔的应用前景。

Characteristics of Amine Surfactant Modified Peanut Shell and Its Sorption Property for Cr（VI）

Modified peanut shell （MPS） was prepared by amination reaction with peanut shell （PS） as the starting material The sorption of Cr（VI） oxyanions on MPS in static and column tests were investigated. In addition, the sorption isotherm and kinetic models were applied to confirm the sorption capacity and the sorption mechanisms. BET surface area anysis showed the physicochemical characterist!cs of the samples. The results of zeta potential,Fourier transform infrared （FT-IR） and Raman spectra analysis illustrated that chemical adsorption and ion exi change are the potential sorption mechanism. The static sorption test showed that the maximum sorption capacity （qm） of MPS for Cr（VI） increased with temperature, which indicated that the Cr（VI） sorption rocess was endothermic. The saturated sorption capacity of Cr（VI） in the colunm sorption test was 138.34 mg.g-1, which accounted for 93.9% of the qmax at 25 ℃. The regeneration capacity of MPS was evaluated using HC1 solution as an eluent. The high regeneration efficiency （82.6%） validated the dominance of the ion exchange mechanism in the Cr（VI） sorption process with C1ions displacing Cr（VI） oxyanion on MPS. The Langmuir isotherm model showed a higher correlation coefficient than the other adsorption isotherm models. And in the kinetic study, a pseudo-second-order model fit the data best.

微纳米黄铁矿对水中Cr(VI)的还原固定研究

通过机械活化的方法对天然黄铁矿进行处理,利用X射线衍射仪(XRD)、高分辨率透射电子显微镜(TEM)对其进行表征,采用批实验的方法探究不同投加量、不同温度和不同pH的条件下,黄铁矿微粒对水中Cr(VI)的还原固定效果。结果表明,经过机械活化之后天然黄铁矿粒径在100 nm左右,达到微纳米级别;黄铁矿微粒对水中Cr(VI)的去除率随着投加量的增加不断增大,1.0 g的黄铁矿微粒可以完全去除浓度为10 mg·L^(-1)的Cr(VI)溶液;随着温度的升高,黄铁矿微粒对水中Cr(VI)的去除率升高,温度为45℃、反应时间为2 h,去除率可以达到97.8%;溶液初始pH值在2~7内,黄铁矿微粒对Cr(VI)的去除率随着pH值的升高逐渐降低,pH为2时去除率最高,为95%;通过尝试动力学拟合,黄铁矿微粒去除水中Cr(VI)的过程符合准二级动力学。

Preparation,characterization and photocatalytic activity of sulfuric acid-modified titanium-bearing blast furnace slag

The feasibility of reducing Cr(VI)from the aqueous solution by sulfuric acid-modified titanium-bearing blast furnace slag(SATBBFS)as a photocatalyst was investigated.The photocatalysts were examined by X-ray diffraction(XRD),UV-vis diffuse reflectance spectra,thermogravimetric analysis(TG)and Fourier transform infrared spectroscopy(FTIR).The photocatalytic activities of the different catalysts were evaluated by the photocatalytic reduction of Cr(VI)under UV-vis light irradiation.The results show that the photocatalytic activities of SATBBFS catalysts are strongly dependent on CaTiO3-to-TiO2 mass ratio,adsorption capacity and surface acidity,and SATBBFS calcined at 400°C shows a higher photocatalytic activity compared with other catalysts.

胶原生物炭/g-C_(3)N_(4)/WO_(3)复合材料光催化去除水体中Cr(Ⅵ)

以制革领域中废弃的皮胶原纤维为原料,基于鞣制化学中的矿物鞣制原理,将钨离子负载在皮胶原纤维上,并经过高温热解得到负载氧化钨的生物炭材料(C/WO_(3)),最后采用机械混合法将石墨相氮化碳(g-C_(3)N_(4))与C/WO_(3)进行复合,制备得到g-C_(3)N_(4)/C/WO_(3)光催化剂。采用扫描电子显微镜、X射线衍射和荧光光谱等进行形貌结构和性能的表征,并且以Cr(Ⅵ)作为目标污染物,研究了g-C_(3)N_(4)/C/WO_(3)对Cr(Ⅵ)的去除效果。结果表明,g-C_(3)N_(4)/C/WO_(3)比表面积达到244.62 m2/g,远高于单独的g-C_(3)N_(4)(9.95 m2/g),同时g-C_(3)N_(4)/C/WO_(3)的光催化性能明显提升。Cr(Ⅵ)的去除实验表明,当催化剂用量为0.1 g,Cr(Ⅵ)初始质量浓度为50 mg/L,溶液pH为2时,g-C_(3)N_(4)/C/WO_(3)对Cr(Ⅵ)的去除率高达99.99%,并且几乎不受水中共存物质的影响,循环性能比较稳定。

High efficient removal and mineralization of Cr(VI)from water by functionalized magnetic fungus nanocomposites

A hydroxyl-functionalized magnetic fungus nanocomposite(MFH@GO)was prepared by a simple one-pot method for the removal of Cr(VI)from wastewater.The adsorption behavior of MFH@GO to Cr(VI)in wastewater was discussed in detail.At pH of 5.0 and temperature of 323.15 K,MFH@GO had higher adsorption capacity to Cr(VI)(58.4 mg/g)than the unmodified fungus and GO.Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),thermogravimetry and differential thermal analysis(TG-DTA),scanning electron microscopy and energy dispersive X-Ray spectroscopy(SEM-EDX)were employed to determine the characteristics of MFH@GO.Results showed that magnetic graphene oxide nanoparticles significantly enhanced the physiochemical properties of the fungi.In addition,the adsorption mechanisms analyses show that Cr(VI)could be reduced and mineralized into ferric chromate in residues.These results suggested that MFH@GO could be used as an promising and alternative biosorbent for removal of Cr(VI)from industrial wastewater.

Removal of Cr (VI) from Aqueous Solution Using Ultrafine Coal Fly Ash

Coal fly ashes WSRA and BQRA were ball milled for 5 h to produce their ultrafine coal fly ashes WSUA and BQUA, respectively. Batch kinetic, isotherm and pH effect on adsorption were studied to evaluate removal of Cr （VI） from aqueous solutions by ultrafine coal fly ashes comparing with raw coal fly ashes. The kinetics of adsorption indicates the process to be intraparticle diffusion controlled and follows the Lagergren first-order kinetics for all coal fly ashes. The first-order rate constants （k1） of Cr （VI） adsorption onto WSRA, WSUA, BQRA and BQUA are 1.981, 1.497, 2.119 and 1.500 （×10^-2） min^-1, respectively. The adsorption capacities of WSUA and BQUA are much better than those of WSRA and BQRA. Equilibrium adsorption data of all coal fly ashes well satisfy the Langmuir isotherm. The adsorbed amounts of Cr （VI） onto WSUA and BQUA decrease from pH 2 to pH 6 and then increase up to pH 12.

Tetraethylenepentamine-functionalized magnetic mesoporous composites as a novel adsorbent for the removal Cr(Ⅲ)-ethylenediaminetetraacetic acid in complex solution

A novel tetraethylenepentamine(TEPA) functionalized magnetic mesoporous silica adsorbent(FNMs/TEPA) was prepared for the adsorption of Cr(Ⅲ)-ethylenediaminetetraacetic acid(EDTA)from wastewater. The characterization of the prepared adsorbent certified that TEPA was modified onto the magnetic mesoporous silicon(FNMs), while FNMs/TEPA maintained the ordered mesoporous and pristine magnetic properties. The batch adsorption experiments demonstrated that TEPA significantly enhanced the removal capacity of the adsorbent for Cr(Ⅲ)-EDTA. FNMs/TEPA exhibited an excellent adsorption property(13.84 mg·g-1) at p H 4.0. Even in the presence of high concentrations of coexisting ions and organic acids, the adsorption performance of FNMs/TEPA was stable. Experimental characterization and DFT demonstrated that the adsorption of Cr(Ⅲ)-EDTA was ascribed to the electrostatic interaction, hydrogen bonding, and complexation between Cr(Ⅲ)-EDTA and amino groups on the adsorbent surface. The analysis of the independent gradient model(IGM) shows that electrostatic interaction is the main mode of action in the adsorption process. Moreover, FNMs/TEPA demonstrated remarkable reusability in three regeneration cycles. These findings indicated that FNMs/TEPA possessed excellent application prospects in the disposal of wastewater containing Cr(Ⅲ)-EDTA.

Heavy metal contamination, physico-chemical and microbial evaluation of water samples collected from chromite mine environment of Sukinda, India

Water samples from chromite mine quarry of Sukinda and its adjacent areas were analyzed for their heavy metal contamination along with physico-chemical and microbial contents. The chromite mine water samples possessed high concentrations of heavy metals in the order of Cr〉Fe〉Zn〉Ni〉Co〉Mn while ground water did not show any heavy metal contamination except Fe. Physico-chemical parameters of mine water samples showed deviation from those of normal water. Mine water harboured low microbial populations of bacteria, fungi and actinomycetes in comparison with mine adjacent water samples. The correlation of data between metals with physico-chemical parameters showed both positive and negative responses while that of metal and microbial population exhibited negative correlation. Bacterial strains isolated from chromite mine water exhibited high tolerance towards chromium and other heavy metals as well as antibiotics which could be used as an indicator of heavy metal pollution.

Spectrophotometric Determination of Trace Chromium(VI) in Mass Chromium(III)

The method for the sepration and determination of trace Cr(VI) exiting in mass Cr(III) has been researched. The method is highly sensitive and less interference, but is simple and useful for analysis trace Cr(VI).

Constructing Cd_(0.5)Zn_(0.5)S/Bi_(2)WO_(6) S-scheme heterojunction for boosted photocatalytic antibiotic oxidation and Cr(VI) reduction

The development of distinguished photocatalysts with high photo-carrier disassociation and photo-redox power for efficient elimination of pollutants in water is of great significance but still a grand challenge.Herein,a novel Cd_(0.5)Zn_(0.5)S/Bi_(2)WO_(6) S-scheme heterojunction was built up by integrating Cd0.5Zn0.5S nanoparticles on Bi2WO6 microspheres via a simple route.The S-scheme charge transfer mode substantially boosts the high-energetic electrons/holes spatial detachment and conservation on the Cd_(0.5)Zn_(0.5)S(reduction)and Bi_(2)WO_(6)(oxidation),respectively,as well as effectively suppresses the photo-corrosion of Cd_(0.5)Zn_(0.5)S,rendering Cd_(0.5)Zn_(0.5)S/Bi_(2)WO_(6) photocatalysts with superior redox ability.The optimal Cd_(0.5)Zn_(0.5)S/Bi_(2)WO_(6) heterojunction achieves exceptional visible-light-driven photocatalytic tetracycline degradation and Cr(VI)reduction efficiency,3.2(1.9)-time and 33.6(1.6)-time stronger than that of neat Bi_(2)WO_(6)(Cd_(0.5)Zn_(0.5)S),while retaining the superior stability and reusability.Quenching test,mass spectrometry analysis,and toxicity assessment based on Quantitative Structure Activity Relationships.calculation unravel the prime active substances,intermediates,photo-degradation pathway,and intermediate eco-toxicity in photocatalytic process.This research not only offers a potential photocatalyst for aquatic environment protection but also promotes the exploration of novel and powerful chalcogenides-based S-scheme photocatalysts for environment protection.

Hexavalent Chromium Removal and Reduction to Cr (III) by Polystyrene Tris(2-aminoethyl)amine

A commercially available chelating polymer, polystyrene tris(2-aminoethyl)amine, was used for the removal of chromium from aqueous solution. The influence of pH, contact time, adsorbent dosage and initial Cr (VI) concentration on adsorption was studied. The optimum pH for the removal of Cr (VI) was at pH 5, while optimum contact time and adsorbent dosage were 120 minutes and 10 g/L, respectively. Total chromium and Cr (VI) concentrations were analyzed by ICP-MS and UV-Visible. Adsorption isotherms using Langmuir and Freundlich isotherm models revealed that the data fitted Langmuir isotherm model better than Freundlich with a maximum adsorption capacity of 312.27 mg/g. FTIR spectroscopy, Scanning electron microscopy (SEM) and Energy Dispersive Spectrometry (EDS) analyses were performed on the adsorbent before and after binding Cr (VI). All analyses confirmed the complexation of Cr (VI) to the adsorbent. Desorption experiments using KCl solution indicated 89.3% release of chromium, rendering this method of high potential for adsorbent regeneration.