Preparation of activated carbon from cattail and its application for dyes removal

Activated carbon was prepared from cattail by H3PO4 activation. The effects influencing the surface area of the resulting activated carbon followed the sequence of activated temperature 〉 activated time 〉 impregnation ratio 〉 impregnation time. The optimum condition was found at an impregnation ratio of 2.5, an impregnation time of 9 hr, an activated temperature of 500℃, and an activated time of 80 min. The Brunauer-Emmett-Teller surface area and average pore size of the activated carbon were 1279 m^2/g and 5.585 nm, respectively. A heterogeneous structure in terms of both size and shape was highly developed and widely distributed on the carbon surface. Some groups containing oxygen and phosphorus were formed, and the carboxyl group was the major oxygen-containing functional group. An isotherm equilibrium study was carried out to investigate the adsorption capacity of the activated carbon. The data fit the Langmuir isotherm equation, with maximum monolayer adsorption capacities of 192.30 mg/g for Neutral Red and 196.08 mg/g for Malachite Green. Dye-exhausted carbon could be regenerated effectively by thermal treatment. The results indicated that cattail-derived activated carbon was a promising adsorbent for the removal of cationic dyes from aqueous solutions.

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.

Green Hydrothermal Synthesis and Applications of Sorbus pohuashanensis/Aronia melanocarpa Extracts Functionalized-Au/Ag/AuAg Nanoparticles

Nanoparticles(NPs)have already been widely used in catalysis,antibacterial and coating fields.Compared with the traditional toxic and harmful reducing reagents,green synthesis of NPs by using plant extracts is not only environmental-friendly and cost-effective but also conducive to the multi-level and efficient utilization of wild plant resources.In this study,the aqueous extracts from Sorbus pohuashanensis(SP)and Aronia melanocarpa(AM)fruits were used as the reducing and protective reagents for synthesizing Au/AgNPs,with the characteristics of originality operation and high repeatability.The SP/AM fruit extracts functionalized Au/AgNPs were characterized by UV-vis spectroscopy(UV-vis),transmission electron microscopy(TEM),energy dispersive spectroscopy(EDS),scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTIR).UV-vis spectrums showed the NPs peaks verified by the presence between 400–550 nm;TEM and SEM demonstrated NPs displayed approximately spherical structures;EDS confirmed the existence of Au/Ag elements;XRD measurements confirmed that the obtained NPs showed highly crystalline structures;FTIR demonstrated the fruits extracts were adsorbed on the surface of NPs.Primary experiments indicated that SP/AM fruit extracts functionalized-NPs could be used as the reagents for removing the organic dyes efficiently;Zone of inhibition tests(ZOI)explained that NPs have slow-release antibacterial activity.

Kinetic and Thermodynamic Study of the Elimination of Remazol Black on Activated Carbon Based on Ricinodendron heudelotii Shells

Activated carbon made from the shells of Ricinodendron heudelotii was used to remove the remazol black dye in aqueous solution. The results of the characterization of this carbon revealed that it is microporous, with a basic global surface (0.337 mmol/L) and a specific surface of 612 m2/g. The prepared carbon therefore has excellent adsorbent properties. Kinetic and thermodynamic studies were carried out to describe the adsorption mechanism of remazol black on this carbon. It appears from this study that the pseudo-second-order kinetic model is the best suited to describe this adsorption phenomenon with an equilibrium time of 200 min. The adsorption equilibrium study revealed that Langmuir and Freundlich models can help to describe the adsorption process. We note that the optimum pH and optimum mass for the removal of 20 mg/L of remazol black are 3 and 0.25 g, respectively. This carbon made it possible to eliminate more than 98% of the remazol dye in aqueous solution. The thermodynamic study revealed that the adsorption is of the physisorption type, spontaneous and endothermic.

La/Ce-codoped Bi_2O_3 composite photocatalysts with high photocatalytic performance in removal of high concentration dye

A series of La/Ce-codoped Bi2O3 composite photocatalysts were fabricated via hydrothermal–calcination process. The as-prepared products were intensively characterized by some physicochemical characterizations like N2 physical adsorption, X-ray powder diffraction（XRD）, scanning electron microscope（SEM）, transmission electron microscope（TEM）, UV–Vis diffuse reflectance（UV–Vis DRS）, Fourier transform infrared spectroscopy（FT-IR）,photoelectrochemical measurements, and photoluminescence（PL） spectroscopy. The characterization results indicated that La and Ce doping induced obvious crystal phase transformation in Bi2O3, from monoclinic to tetragonal phase. La and Ce codoping also gave rise to the obvious synergetic effects, e.g., the lattice contraction of Bi2O3, the decrease of crystal size and the increase of surface area. The photocatalytic performance of the prepared catalysts was evaluated by removal of dye acid orange II with high concentration under visible light irradiation. Results showed that La/Ce-codoped Bi2O3 displayed much higher photocatalytic performance than that of bare Bi2O3, single La or Ce doped Bi2O3 samples. The superior photocatalytic activity was mainly attributed to the improved texture and surface properties and the synergistic effects of La and Ce codoping on suppressing the recombination of photo-generated electrons（e^-） and holes（h~＋）.

Electrocatalytic biofilm reactor for effective and energyefficient azo dye degradation:the synergistic effect of MnO_(x)/Ti flow-through anode and biofilm on the cathode

Dyeing wastewater treatment remains a challenge.Although effective,the in-series process using electrochemical oxidation as the pre-or post-treatment of biodegradation is long.This study proposes a compact dual-chamber electrocatalytic biofilm reactor(ECBR)to complete azo dye decolorization and mineralization in a single unit via anodic oxidation on a MnO_(x)/Ti flow-through anode followed by cathodic biodegradation on carbon felts.Compared with the electrocatalytic reactor with a stainlesssteel cathode(ECR-SS)and the biofilm reactor(BR),the ECBR increased the chemical oxygen demand(COD)removal efficiency by 24%and 31%(600 mg/L Acid Orange 7 as the feed,current of 6 mA),respectively.The COD removal efficiency of the ECBR was even higher than the sum of those of ECR-SS and BR.The ECBR also reduced the energy consumption(3.07 kWh/kg COD)by approximately half compared with ECR-SS.The advantages of the ECBR in azo dye removal were attributed to the synergistic effect of the MnO_(x)/Ti flow-through anode and cathodic biofilms.Catalyzed by MnIV=O generated on the MnO_(x)/Ti anode under a low applied current,azo dyes were oxidized and decolored.The intermediate products with improved biodegradability were further mineralized by the cathodic aerobic heterotrophic bacteria(non-electrochemically active)under the stimulation of the applied current.Taking advantage of the mutual interactions among the electricity,anode,and bacteria,this study provides a novel and compact process for the effective and energyefficient treatment of azo dye wastewater.

Hierarchical BiOBr microspheres with oxygen vacancies synthesized via reactable ionic liquids for dyes removal

Hierarchical BiOBr microspheres with oxygen vacancies, which can be used for the dyes removal, have been synthesized successfully in the presence of different kinds of ionic liquids. It was revealed that BiOBr prepared by the ionic liquids with short chain length exhibited higher photocatalytic activity in the degradation of methyl orange （MO） under visible light. The experimental results showed that the phenomenon of the photocatalytic degradation of MO can be explained by the photoluminescence spectra.

Effect of viscosity,basicity and organic content of composite flocculant on the decolorization performance and mechanism for reactive dyeing wastewater

A coagulation/flocculation process using the composite flocculant polyaluminum chloride-epichlorohydrin dimethylamine （PAC- EPI-DMA） was employed for the treatment of an anionic azo dye （Reactive Brilliant Red K-2BP dye）. The effect of viscosity 01）, basicity （B = [OH]/[Al]） and organic content （Wp） on the flocculation performance as well as the mechanism of PAC-EPI-DMA flocculant were investigated. The η was the key factor affecting the dye removal efficiency of PAC-EPI-DMA. PAC-EPI-DMA with an intermediate η （2400 mPa.sec） gave higher decolorization efficiency by adsorption bridging and charge neutralization due to the co-effect of PAC and EPI-DMA polymers. The Wp of the composite flocculant was a minor important factor for the flocculation. The adsorption bridging of PAC-EPI-DMA with η of 300 or 4300 mPa.sec played an important role with the increase of Wp, whereas the charge neutralization of them was weaker with the increase of Wp. There was interaction between Wp and B on the removal of reactive dye. The composite flocculant with intermediate viscosity and organic content was effective for the treatment of reactive dyeing wastewater, which could achieve high reactive dye removal efficiency with low organic dosage.

Preparation and properties of chitosan–metal complex：Some factors influencing the adsorption capacity for dyes in aqueous solution

Chitosan–metal complexes have been widely studied in wastewater treatment, but there are still various factors in complex preparation which are collectively responsible for improving the adsorption capacity need to be further studied. Thus, this study investigates the factors affecting the adsorption ability of chitosan–metal complex adsorbents, including various kinds of metal centers, different metal salts and crosslinking degree. The results show that the chitosan–Fe（ Ⅲ） complex prepared by sulfate salts exhibited the best adsorption efficiency（100%） for various dyes in very short time duration（10 min）, and its maximum adsorption capacity achieved 349.22 mg/g. The anion of the metal salt which was used in preparation played an important role to enhance the adsorption ability of chitosan–metal complex. SO4^（2-） ions not only had the effect of crosslinking through electrostatic interaction with amine group of chitosan polymer, but also could facilitate the chelation of metal ions with chitosan polymer during the synthesis process.Additionally, the p H sensitivity and the sensitivity of ionic environment for chitosan–metal complex were analyzed. We hope that these factors affecting the adsorption of the chitosan–metal complex can help not only in optimizing its use but also in designing new chitosan–metal based complexes.

Facile and scalable preparation of ZIF-67 decorated cotton fibers as recoverable and efficient adsorbents for removal of malachite green

Recently,metal–organic frameworks(MOFs)have received considerable attention as highly efficient adsorbents for dye wastewater remediation.However,the immobilization of MOFs on the substrate surfaces to fabricate easy recy-clable adsorbents via a facile route is still a challenge.In this work,ZIF-67/cotton fibers as adsorbents for dye removal were prepared in a large-scale using a simple coordination replication method.The successful fabrication of the ZIF-67/cotton fibers was confirmed by FTIR,XRD,XPS,SEM and BET analysis,respectively.As expected,the as-prepared ZIF-67/cotton fibers exhibited high adsorption capacity of 3787 mg/g towards malachite green(MG).Meanwhile,the adsorption kinetics and isotherm obeyed the pseudo-second-order kinetics and Langmuir model,respectively.Moreover,its removal efficiency towards MG was not significantly influenced by the pH and ionic strength of aque-ous solution.Most importantly,the ZIF-67/cotton fibers can remove MG from synthetic effluents,and it can be easily regenerated without filtration or centrifugation processes,with the regeneration efficiency remaining over 90%even after 10 cycles.Additionally,the ZIF-67/cotton fibers presented excellent antimicrobial performance against E.coli and S.aureus.Hence,the distinctive features of the as-prepared ZIF-67/cotton fibers make it promisingly applicable for the colored wastewater treatment.

Kinetics and thermodynamic studies of Methyl Orange removal by polyvinylidene fluoride-PEDOT mats

We report the preparation of poly(3,4-ethylene dioxythiophene)(PEDOT)-modified polyvinylidene fluoride electrospun fibers and their use as a novel adsorbent material for the removal of the anionic dye Methyl Orange(MO)from aqueous media.This novel adsorbent material can be used to selectively remove MO on a wide p H range(3.0-10.0),with a maximum capacity of 143.8 mg/g at p H 3.0.When used in a recirculating filtration system,the maximum absorption capacity was reached in a shorter time(20 min)than that observed for batch mode experiments(360 min).Based on the analyses of the kinetics and adsorption isotherm data,one can conclude that the predominant mechanism of interaction between the membrane and the dissolved dye molecules is electrostatic.Besides,considering the estimated values for the Gibbs energy,and entropy and enthalpy changes,it was established that the adsorption process is spontaneous and occurs in an endothermic manner.The good mechanical and environmental stability of these membranes allowed their use in at least 20 consecutive adsorption/desorption cycles,without significant loss of their characteristics.We suggest that the physical-chemical characteristics of PEDOT make these hybrid mats a promising adsorbent material for use in water remediation protocols and effluent treatment systems.

Strong enhancement of methylene blue removal from binary wastewater by in-situ ferrite process

Dye wastewater containing heavy metal ions is a common industrial effluent with complex physicochemical properties. The treatment of metal-dye binary wastewater is difficult. In this work, a novel in-situ ferrite process （IFP） was applied to treat Methylene Blue （MB）-Cu（II） binary wastewater, and the operational parameters were optimized for MB removal. Results showed that the optimum operating conditions were OH/M of 1.72, Cu2＋/Fe2＋ ratio of 1/2.5, reaction time of 90 min, aeration intensity of 320 mL/min, and reaction temperature of 40℃. Moreover, the presence of Ca2＋ and Mg2＋ moderately influenced the MB removal. Physical characterization results indicated that the precipitates yielded in IFP presented high surface area {232.50 m2/g） and a multi-porous structure. Based on the Langmuir model, the maximum adsorption capacity toward MB was 347.82 mg/g for the precipitates produced in IFP, which outperformed most other adsorbents. Furthermore, IFP rapidly sequestered MB with removal efficiency 5 to 10 times greater than that by general ferrite adsorption, which suggested a strong enhancement of MB removal by IFP. The MB removal process by IFP showed two different high removal stages, each with a corresponding removal mechanism. In the first brief stage （〈5 min）, the initial high MB removal （～95%） was achieved by predominantly electrostatic interactions. Then the sweep effect and encapsulation were dominant in the second longer stage.

Rapid degradation of dyes in water by magnetic Fe^0/Fe_3O_4/graphene composites

Magnetic Fe^0/Fe3O4/graphene has been successfully synthesized by a one-step reduction method and investigated in rapid degradation of dyes in this work. The material was characterized by N2 sorption–desorption, scanning electron microscopy（SEM）, Fourier transform infrared spectroscopy（FT-IR）, vibrating-sample magnetometer（VSM） measurements and X-ray photoelectron spectroscopy（XPS）. The results indicated that Fe^0/Fe3O4/graphene had a layered structure with Fe crystals highly dispersed in the interlayers of graphene, which could enhance the mass transfer process between Fe^0/Fe3O4/graphene and pollutants. Fe^0/Fe3O4/graphene exhibited ferromagnetism and could be easily separated and re-dispersed for reuse in water. Typical dyes, such as Methyl Orange, Methylene Blue and Crystal Violet, could be decolorized by Fe^0/Fe3O4/graphene rapidly. After 20 min, the decolorization efficiencies of methyl orange, methylene blue and crystal violet were 94.78%, 91.60% and 89.07%, respectively. The reaction mechanism of Fe^0/Fe3O4/graphene with dyes mainly included adsorption and enhanced reduction by the composite. Thus, Fe^0/Fe3O4/graphene prepared by the one-step reduction method has excellent performance in removal of dyes in water.

One-step synthesis of Cu(Ⅱ) metal–organic gel as recyclable material for rapid, efficient and size selective cationic dyes adsorption

Efficient removal of non-biodegradable and hazardous dyes from wastewater remains a hot research topic.Herein,a rationally designed a Cu(Ⅱ)-based metal–organic gel(Cu-MOG)with a nanoporous 3 D network structure prepared via a simple one-step mixing method was successfully employed for the removal of cationic dyes.The Cu-MOG exhibited high efficiency,with an adsorption capacity of up to 650.32 mg/g,and rapid adsorption efficiency,with the ability to adsorb 80%of Neutral Red within 1 min.The high adsorption efficiency was attributed to its large specific surface area,which enabled it to massively bind cationic dyes through electrostatic interaction,and a nanoporous structure that promoted intra-pore diffusion.Remarkably,the Cu-MOG displayed size-selective adsorption,based on adsorption studies concerning dyes of different sizes as calculated by density functional theory.Additionally,the adsorption performance of the Cu-MOG still maintained removal efficiency of 100%after three regeneration cycles.These results suggested that the Cu-MOG could be expected to be a promising and competitive candidate to conveniently process wastewater.

Using silk-derived magnetic carbon nanocomposites as highly efficient Nanozymes and electromagnetic absorbing agents

Functional carbon nanomaterials have become the stars of many active research fields,such as electronics,energy,catalysis,imaging,sensing and biomedicine.Herein,a facile and one-pot strategy for generating ferromagnetic nanoparticles loaded on N-doped carbon nanosheets(Fe-N-CNS)is presented by salt-assisted high-temperature carbonization of natural silk proteins.Due to their graphitic structures,N-doping and ferromagnetic nanoparticles(FeN_(x),FeO_(y),FeC_(z)),the silk-derived Fe-N-CNS can act as excellent mimics of both peroxidase and oxidase.Benefiting from the combined character of the graphene-like structures and enzyme-like activities,Fe-N-CNS can be further applied to highly efficient dye removal via synergistic adsorption and degradation.Meanwhile,the as-prepared Fe-N-CNS with intrinsic magnetism and electrical conductivity can also serve as an efficient electromagnetic wave absorption agent.The broadest effective absorption bandwidth(EAB)of as-obtained absorbing material yields a 6.73 GHz with 1 mm thickness,with a maximum reflection loss of-37.33 dB(11.41 GHz).The EAB can cover2~18 GHz with a tunable absorber thickness from 1.0 mm to 5.0 mm.Collectively,Fe-N-CNS,as a dualfunctional material,can tackle the aggravating environmental pollution issues of both dyes and electromagnetic waves.

Air-Steam Etched Construction of Hierarchically Porous Metal-Organic Frameworks

The introduction of mesoporosity into the microporous metal-organic frameworks(MOFs)is expected to expand their applications.Herein,we report a green and facile method to obtain hierarchically porous MOF structures by using an air-steam etching process.By virtue of the protonation reaction between the imidazole moiety and water vapor,the protonated imidazole related linkers leave the framework,resulting in the formation of mesopores in the zeolitic imidazolate frameworks(ZIFs),as exemplified by ZIF-8.Given the mild etching process,the materials'structural integrity and crystallinity are well maintained.Accordingly,the hierarchical porous ZIF-8 exhibited enhanced performance in the dye removal as well as CO_(2) cycloaddition reaction with epichlorohydrin in comparison with microporous ZIF-8,owing to the accelerated mass transfer arising from mesoporous structures.Remarkably,the proposed steam etching approach is generally applicable,which can be readily extended to other ZIFs,such as ZIF-14,ZIF-69,and ZIF-71,thus representing a powerful strategy to construct hierarchically porous MOF materials.

Ferric ion-ascorbic acid complex catalyzed calcium peroxide for organic wastewater treatment:Optimized by response surface method

Hydrogen peroxide(H_(2)O_(2))disproportionation,iron precipitation,and narrow pH range are the drawbacks of traditional Fenton process.To surmount these barriers,we proposed a ferric ion(Fe^(3+))-ascorbic acid(AA)complex catalyzed calcium peroxide(CaO_(2))Fenton-like system to remove organic dyes in water.This collaborative Fe^(3+)/AA/CaO_(2)system presented an obvious improvement in the methyl orange(MO)decolorization,and also effectively eliminated other dyes.Response surface method was employed to optimize the running parameters for this coupling process.Under the optimized arguments(2.76 mmol/L Fe^(3+),0.68 mmol/L AA,and 4 mmol/L CaO_(2)),the MO removal achieved 98.90%after 15 min at pH 6.50,which was close to the computed outcome of 99.30%.Furthermore,this Fenton-like system could perform well in a wide range of pH(3-11),and enhance the H_(2)O_(2)decomposition and Fe ions recycle.The scavenger experiment result indicated that hydroxyl radical,superoxide anion free radical,and singlet oxygen were acted on the dye elimination.Moreover,electron spin resonance analysis corroborated that the existences of these active species in the Fe^(3+)/AA/CaO_(2)system.This study could advance the development of Fenton-like technique in organic effluent disposal.

Strengthening of polysulfone membranes using hybrid mixtures of micro- and nano-scale modifiers

Polysulfone （PSf） membranes were modified by either a new organic modifier （sulfonated poly（ether sulfide sulfone）, SPESS） or a traditional modifier （rice hulk）. These membranes were further reinforced with either multi-walled carbon nanotubes （MWCNTs） or silica nanoparticles. Having a dye rejection of 98.46%, the reinforced membranes increased more than 50% in strength but no change in solution flux was observed. The morphological and roughness studies were conducted using scanning electron microscopy and atomic force microscopy. Moreover, the PSF membranes were also characterized by differential scanning calorimetry. Modifying the membranes with organic modifier or nanofiller increases the glass transition temperature （Tg）. The highest Tg and strength were observed for the PSf-SPESS- MWCNT membrane. SPESS decreases surface roughness but MWCNT increases roughness on the nanoscale. All membranes show a bimodal pore size distribution, whereas the PSf-SPESS-MWCNT membrane exhibits a relatively uniform distribution of macroscopic and microscopic pores.

Sulfonation of Hydroxymethylated Lignin and Its Application

To valorize kraft lignin,hydroxymethylation and sulfonation were applied on this under-utilized,but vastly available,material.The hydroxymethylation pretreatment was conducted as means to improve the reactivity of lignin.The sulfonation of hydroxymethylated kraft lignin was investigated by sulfuric acid and sodium sulfite treatments under various conditions.The modified lignin samples were characterized for their charge density,solubility,elemental components,and molecular weights.The results showed that the hydroxymethylation facilitated the sulfonation by sodium sulfite,yielding a product(SSH-lignin)with the charge density of-1.2 meq/g and water solubility of 10 g/L under the conditions of Ns_(2)SO_(3)/lignin molar ratio of 0.49 mol/mol,95℃and 3 h.On the other hand,hydroxymethylation hindered the sulfonation of lignin by sulfuric acid,yielding a product(SAH-lignin)with the charge density of–0.46 meq/g and solubility of 0.9 g/L under the conditions of H_(2)SO_(4)/lignin molar ratio of 14.8 mol/mol,80℃and 1 h.The SSH-lignin had a high adsorption on kaolinite(17 mg/g)at a lignin concentration of 40 g/L.The sulfonated lignins were also found to be effective coagulant for the cationic dye ethyl violet.

Heterojunction architecture of Nb_(2)O_(5)/g-C_(3)N_(4)for enhancing photocatalytic activity to degrade organic pollutants and deactivate bacteria in water

Water pollution has become a serious problem owing to the development of society.Photocatalysis is a promising approach to remove various pollutants in water,such as organic pollutants and antibiotic resistance bacteria.Meanwhile,the design of heterojunction between two semiconductors is an effective path to improve photocatalytic properties due to its potential in improving separation and transfer of photoinduced carriers.In this study,Nb_(2)O_(5)/g-C_(3)N_(4)(NO/CN)composite materials were prepared through a one-step heating method.Characterizations confirmed successful preparation of NO/CN heterojunction structure and better optical properties than pure g-C_(3)N_(4) and Nb_(2)O_(5).NO/CN composite materials showed excellent photocatalytic efficiency for Escherichia coli(E.coli)inactivation(95%)compared with the pure Nb_(2)O_(5)(10%) and g-C_(3)N_(4)(77%).Meanwhile,NO/CN exhibited better organic pollutants removal(Rh B for94%,methyl orange(MO)for 15%and methylene blue(MB)for 87%)under visible light,which is likely owing to the heterojunction structure between g-C_(3)N_(4) and Nb_(2)O_(5) that leads to the good separation of photogenerated electron-hole pair.Free radical scavenging and electron spin resonance(ESR)experiments demonstrated that superoxide radicals(·O_(2)^(-)) and holes(h^(+)) were the dominant radicals.Therefore,the NO/CN was proposed to be a promising material for effective disinfection and removal of organic contaminants in water treatment.