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Removal of hexavalent chromium from contaminated waters by ultrasound-assisted aqueous solution ball milling

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Journal of Environmental Sciences 2017年第2期29卷 276-283页

作者： Lin Chen Zhenhua Chen Ding Chen Wei Xiong College of Materials Science and Engineering Hunan UniversityChangsha 410082China

Batch mode experiments were conducted to study the removal of hexavalent chromium（cr（Ⅵ）） from aqueous solutions using ultrasound-assisted aqueous solution ball milling.The results show that the reduction rate of cr（Ⅵ） by ultrasound-assisted aqueous solution ball milling was significantly faster than that by ball milling or ultrasound treatment alone,and an initial cr（Ⅵ） concentration of 166 mg/L could be decreased to 0.35 mg/L at 120 min.The decisive factors, including initial concentration of cr（Ⅵ）, p H value, ultrasonic frequency and filling gas, were studied. It was found that the optimal ultrasonic frequency for ultrasound-assisted aqueous solution ball milling device was 20 k Hz, and the rate of cr（Ⅵ）reduction as a function of filling gas followed the order： Ar 〉 air 〉 N2〉 O2. Samples were characterized by X-ray diffraction, fluorescence measurements, atomic absorption and the diphenylcarbazide colorimetric method. The cr（Ⅵ） transformed into a precipitate that could be removed from the contaminated water, after which the water could be reused.

关键词： cr（vi） Ultrasound wave Ball milling Hydroxyl radicals

Preparation of cross-linked magnetic chitosan with quaternary ammonium and its application for cr(Ⅵ) and P(Ⅴ) removal

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Journal of Environmental Sciences 2014年第12期26卷 2379-2386页

作者： Wei Yao Pinhua Rao Irene M.C.Lo Wenqi Zhang Wenrui Zheng School of Chemistry and Chemical Engineering Shanghai University of Engineering Science Department of Civil and Environmental Engineering The Hong Kong University of Science and Technology

Pollutants that exist in anionic species are issues of concern in water treatment. Compared to cationic pollutants, the removal of anionic pollutants by adsorption is more difficult because most adsorbents carry predominantly negative charges in neutral and alkaline environments. In this study, a cross-linked chitosan derivative with quaternary ammonium and magnetic properties（QM-chitosan） was prepared and employed to remove chromium（vi） and phosphorus（V）（cr（vi） and P（V）） from aqueous environments. The QM-chitosan was characterized by Fourier transform infrared spectrometry（FT-IR）,thermogravimetric analysis（TGA）, energy dispersive X-ray（SEM-EDX） and zeta potential.Batch experiments show that QM-chitosan can effectively remove cr（vi） and P（V）, and the main mechanism was believed to be electrostatic interaction. A pseudosecond-order model was fitted to describe the kinetic processes of cr（vi） and P（V） removal. The adsorption isotherms of both cr（vi） and P（V） on the QM-chitosan were well fitted by the Langmuir isotherm equation. The saturated adsorption capacity of P（V）（2.783 mmol/g） was found to be higher than that of cr（vi）（2.323 mmol/g）, resulting from the size of the H2PO-4ions being smaller than that of the Hcr O-4ions. However, the theoretical calculation and experimental results showed that QM-chitosan had a stronger affinity for cr（vi） than P（V）. The adsorption–desorption of the QM-chitosan was evaluated, and high regeneration rates were demonstrated.

关键词： Magnetic chitosan Quaternary ammonium cr（vi） P（V） Adsorption

Formation of willow leaf-like structures composed of NH2-MIL68（In） on a multifunctional multiwalled carbon nanotube backbone for enhanced photocatalytic reduction of cr（vi）

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Nano Research 2017年第10期10卷 3543-3556页

作者： Yunhong Pi Xiyi Li Qibin Xia Junliang Wu Zhong Li Yingwei Li Jing Xiao School of Chemistry and Chemical Engineering South China University of Technology Guangzhou 510640 China Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control South China University of Technology Guangzhou 510640 China

Efficient separation and transfer of photogenerated electron/hole as well as enhanced visible light absorption play essential roles in photocatalytic reactions. To promote the photocatalytic reduction of cr（vi）, a toxic heavy metal ion, multiwalled carbon nanotube （MWCNT） was introduced as an electron acceptor into NH2-MIL-68（In）. This led to the growth of a willow leaf-like metal-organic framework （MOF） on an MWCNT backbone forming MWCNT/NH2-MIL-68（In）（PL-1）, which showed a highly efficient transfer of photogenerated carriers. Moreover, MWCNT incorporation introduced more mesopores for cr（vi） diffusion and enhanced the visible light adsorption without lowering the conduction band position. As a result, the photocatalytic kinetic constant of PL-1 was found to be almost three times higher than that of the parent NH2-MIL-68（In）. Thus, growing MOFs on MWCNTs provides a facile and promising solution for effective remediation of environmental pollution by utilizing solar energy. This work provides the first example of using MWCNT/MOF composites for photocatalytic reactions.

关键词： NH2-MIL-68（In） multiwalled carbon nanotube （MWCNT） photocatalytic reduction cr（vi）

Preparation and characterization of β-FeOOH-coated sand and its adsorption of cr（vi） from aqueous solutions

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Frontiers of Environmental Science & Engineering 2012年第4期6卷 455-462页

作者： Chunhua XU Dandan CHENG Baoyu GAO Zhilei YIN Qinyan YUE Xian ZHAO Shandong Key Laboratory of Water Pollution Control and Resource Reuse School of Environmental Science and EngineeringShandong UniversityJinan 250100China State Key Laboratory of crystal Materials Shandong UniversityJinan 250100China School of Chemistry and Chemical Engineering Shandong UniversityJinan 250100China

Batch adsorption experiments were conducted to explore the adsorption of cr（vi） in aqueous solutions by fl-FeOOH-coated sand. We investigated the key factors which affected the adsorption process such as adsorbent dosage, initial pH, initial cr（vi） ion concentration, contact time and temperature. The uptake of cr（vi） was very rapid and 44.3%, 51.6%, 58.9% of the adsorption happened during the first 180minutes at 293K, 303K and 313K, respectively. The pseudo-second-order rate equation successfully described the adsorption kinetics. To study the adsorption isotherm, two equilibrium models, the Langmuir and Freundlich isotherms, were adopted. At 293K, 303K and 313K, the adsorption capacities obtained from the Langmuir isotherm were 0.060, 0.070 and 0.076 mg cr（vi） per gram of the adsorbent, respectively. Thermodynamic parameters such as the change of energy, enthalpy and entropy were calculated using the equilibrium constants. The negative value of AGO and the positive value of △H^0 showed that the adsorption of cr（vi） in aqueous solutions by β-FeOOH-coated sand was spontaneous, endothermic and occurred by physisorption.

关键词： β-FeOOH-coated sand cr（vi） adsorption isotherm kinetics

The biosorption of cr（vi） ions by dried biomass obtained from a chromium-resistant bacterium

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Frontiers of Chemical Science and Engineering 2014年第4期8卷 454-464页

作者： Paul Fabrice NGUEMA Zejiao LUO Jingjing LIAN State Key Laboratory of Biogeology and Environmental Geology Ministry of Education (BGEG) School of Environmental Studies China University of Geosciences Wuhan 430074 China Schools of Earth Environment and Water Resources Yangtze University Wuhan 430100 China

The biosorption potential of many different kinds of biomaterials has been widely studied. However, there is little data on the biosorption mechanism of cr（vi） by dried biomass. So the bio-removal of cr（vi） ions from aqueous solutions was investigated using dried biomass from a chromium-resistant bacterium. The bacterium was isolated from dewatered sludge samples that were obtained from a sewage treatment plant. Equilibrium and kinetic experiments were performed at different metal concentra- tions, pH values, and biosorbents dosages. The biomass was characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The functional groups in the Bacillus cereus biomass which may play a role in the biosorption process were identified by Fourier transform infrared spectroscopy. The biosorption process was found to be highly pH dependent and the optimum pH for the adsorption of cr（vi） was 2.0：k0.3 at 30-4-2 ℃. The experimental data fit well with Langmuir and Freundlich models as well as a pseudo-second order kinetic model. The mechanism for the biosorption was also studied by fitting the kinetic data with an intra-particle diffusion model and a Boyd plot. External mass transfer was found to be the rate-determining step for the adsorption process. Biosorption could be an alternative mechanism besides bio-oxidation and bio-reduction for the bioremediation of heavy metals.

关键词： Bacillus cereus Pf-1 biosorption capacity,biosorbents cr（vi） biomass

Biosorption of cr（vi） by carbonized Eupatorium adenophorum and Buckwheat straw： thermodynamics and mechanism

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Frontiers of Environmental Science & Engineering 2014年第6期8卷 960-966页

作者： Jinfa CHEN Ping YANG Dagang SONG Sha YANG Li ZHOU Lei HAN Bo LAI Department of Agricultural Science Xichang College Xichang 615013 China College of Architecture & Environment Sichuan University Chengdu 610065 China

High quality and low cost carbon can be prepared from Eupatorium adenophorum （E. adenophorum） and Buckwheat straw. The biosorbent was used for cr（vi） removal. The effect of experimental parameters, such as pH, sorbent dosage and temperature were examined and the optimal experimental condition was determned. Solution pH is found influencing the adsorp- tion. cr（vi） removal efficiency is found to be maximum （98%） at pH= 1. Langmuir and Freundlich adsorption isotherms were applicable to the adsorption process and their constants were evaluated. The adsorption data obtained agreed well with the Langmuir sorption isotherm model. The maximum adsorption capacities for cr（vi） ranged from 46.23 to 55.19mg.g^-1 for temperature between 298 K and 308 K under the condition of pH = 1.0. Thermodynamic parameters such as free energy change （AG）, enthalpy （AH） and entropy （AS） indicate a spontaneous, endothermic and increased randomness nature of cr（vi） adsorption. Studies found that the raw E. adenophorum and buckwheat straw mixed materials with simple treatment had a high efficiency for the removal of cr（vi） and would be a promising adsorbent.

关键词： Eupatorium adenophorum buckwheat straw adsorption cr（vi） thermodynamics

Preliminary Research on cr(vi) Removal by Bacterial Cellulose

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Journal of Wuhan University of Technology(Materials Science) 2012年第3期27卷 572-575页

作者：鲁敏 School of Chemical Engineering Northeast Dianli University

The bacterial cellulose prepared by ourselves was used in the adsorption of cr（vi）. The effects of performance parameters such as adsorption time, pH, the adsorbent dosage on cr（vi） were investigated. Results showed that pH was a very important parameter to the adsorbed efficiency. Removal rate of cr（vi） approached to 15% under the condition of pH 1.5, adsorbent dosage 1.0 gL-1 and co（initial concentration of cr）50 mgL-1. The saturated monolayer adsorption quantity was 5.13 mg/g dry BC. The adsorption rate could be well fitted by pseudo-second rate model, adsorption isotherm could be described by Langmuir model, and they have good linear. Typical single-molecule layer adsorption of bacterial cellulose for cr（vi） could be descripted and electrostatic force was one of the main sorption mechanisms. HCl can desorb the cr（vi） from the adsorbent effectively.

关键词： bacterial cellulose cr（vi） removal

Cellulose Functionalization via ATRP Grafting of Glycidyl Methacrylate for cr（vi） Adsorption

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Chinese Journal of Chemistry 2013年第12期31卷 1551-1556页

作者： Chunxiang Lin Sha Qiao Danhui Liu Minghua Liu College of Environment & Resources Fuzhou University Fuzhou Fuj ian 350108 China

Cellulose was first grafted with glycidyl methacrylate （GMA） in an ionic liquid via atom transfer radical polymerization （ATRP） and then the introduced epoxy groups were reacted with ethanediamine （EDA） to obtain an amino adsorbent. The grafting copolymer and the obtained adsorbent were characterized by FTIR, aH NMR, TEM and SEM. The results showed that the grafted copolymers had grafted polymer chains with well-controlled molecu- lar weight and polydispersity, the polymerization was a controlled system. The cellulose adsorbent had numerous micropores on the surface and showed high performance for cr（vi） adsorption. The adsorption behavior was pH dependent and the sorption equilibrium was achieved within 2 h on the adsorbent.

关键词： cellulose functionalization atom transfer radical polymerization （ATRP） ionic liquid sorption cr（vi）

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

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Geoscience Frontiers 2012年第4期3卷 523-539页

作者： M.Economou-Eliopoulos D.Antivachi Ch.Vasilatos I.Megremi Department of Geology & Geoenvironment Section of Economic Geology & Geochemistry.University of AthensPanepistimiopolisAthens 15784Greece

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 he

关键词： cr（vi） Contamination Plants Groundwater Bio-accumulation Thiva