One-step crosslinking preparation of tannic acid particles for the adsorption and separation of cationic dyes

In this study,a new tannic acid adsorbent(ethylene glycol diglycidyl ether crosslinked tannic acid,TAEGDE)for adsorptive removal of dyes from water was prepared using EGDE as a cross-linking agent.The resultant TA-EGDE was in particulate form with rough surface morphology and a diameter ranging from 10 to 30μm.The adsorption performance of the TA-EGDE was evaluated in a flow-through mode using water samples contaminated with methylene blue(MB)and two-component mixed dyes,respectively.The TA-EGDE provided adsorption capacity up to 721.8 mg·g^(-1)at 65°C for MB.It showed a high removal efficiency(99%)of MB(50 mg·L^(-1))from the water sample and could recovery 90%of the adsorbed MB by eluting with acidic ethanol aqueous solution.The excellent adsorption of MB and neutral red on the TA-EGDE may be the result of the synergy of electrostatic interaction andπ-πinteraction.Furthermore,the TA-EGDE could separate dyes from water samples contaminated with twocomponent mixed dyes with a separation coefficient ranging from 1.8 to 36.5.The anionic TA-EGDE would be an effective adsorbent to remove and recycle dyes from the contaminated water.

Poly (Acrylamide-co-Acrylic Acid) Hydrogel Induced by Glow-Discharge Electrolysis Plasma and Its Adsorption Properties for Cationic Dyes

In this paper, poly （acrylamide-co-acrylic acid） （P（AM-co-AA）） hydrogel was pre- pared in an aqueous solution by using glow-discharge electrolysis plasma （GDEP） induced copoly- merization of acrylamide （AM） and acrylic acid （AA）, in which N,N＇-methylenebisacrylamide （MBA） was used as a crosslinker. A mechanism for the synthesis of P（AM-co-AA） hydrogel was proposed. To optimize the synthesis condition, the following parameters were examined in detail： the discharge voltage, discharge time, the content of the crosslinker, and the mass ratio of AM to AA. The results showed that the optimum pH range for cationic dyes removal was found to be 5.0-10.0. The P（AM-co-AA） hydrogel exhibits a very high adsorption potential and the ex- perimental adsorption capacities for Crystal violet （CV） and Methylene blue （MB） were 2974.3 mg/g and 2303.6 mg/g, respectively. The adsorption process follows a pseudo-second-order kinetic model. In addition, the adsorption mechanism of P（AM-co-AA） hydrogel for cationic dyes was also discussed.

Adsorption of cationic dyes from aqueous solution using hydrophilic silica aerogel via ambient pressure drying

In order to remove the organic dyes of textile waste water,the silica aerogel was successfully prepared by using E-40 as a novel precursor and then dried in ambient pressure.The synthesized sample was verified by Scanning Electron Microscopy(SEM)and Fourier Transform Infrared Spectroscopy(FTIR).After calcining,the hydrophilic silica aerogel(HSA)was used as adsorbent to remove Methylene Blue(MB),Malachite Green(MG),and Gentian Violet(GV)from aqueous solution.The effects of initial concentration of dyes and adsorbent dosage on the adsorption process were examined.It was found that HSA showed excellent adsorption capacities,the maximum percentage of removal dyes could reach 98%.Herein,the Langmuir,Freundlich and de Boer-Zwikker isotherm modes were employed to discuss the adsorption behavior.The results indicated that the de Boer–Zwikker model can effectively describe the adsorption behavior.Besides,the HSA could be utilized as the recyclable adsorbent in degradation experiment,after five cycles,no obvious loss of adsorption capacity was found.As an efficient,low-cost,environmental friendly and recyclable adsorbent,silica aerogel is expected to be used for dyes removal.

Fabrication of porous adsorbents from eco-friendly aqueous foam for high-efficient removal of cationic dyes and sustainable utilization assessment

Porous materials applied in environmental remediation have received researchers'extensive attention recently,but the related green and convenient preparation method is rarely reported.Here,we recommended a green and convenient strategy for the fabrication of porous material via aqueous foam templates,which was synergistically stabilized by Codonopsis pilosula(CP)and clay minerals of attapulgite(APT).The characterization results revealed that the APT was modified by organic molecules leached from CP and anchored at the air-water interface,which improved the foam stability significantly.The novel porous material of polyacrylamide/Codonopsis pilosula/attapulgite(PAM/CP/APT)templated from the aqueous foam via a polymerization reaction had excellent adsorption capacity for the cationic dyes methyl violet(MV)and methylene blue(MB),and the adsorption capacity can reach 755.85 mg/g and557.64 mg/g,respectively.More importantly,the adsorption capacity of spent adsorbent material was still over 200 mg/g after being recycled five times through a simple carbonization process,and then it was added to the plant pot,the total biomass was increased by about86.42%.This study provided a green and sustainable pathway for the preparation,application and subsequent processing of porous materials.

Recyclable hydrolyzed polymers of intrinsic microporosity-1/Fe_(3)O_(4) magnetic composites as adsorbents for selective cationic dye adsorption

Polymers of intrinsic microporosity shows great potential for dye adsorption and magnetic Fe_(3)O_(4) are easy to be separated.In this work,hydrolyzed polymers of intrinsic microporosity-1/Fe_(3)O_(4) composite adsorbents were prepared by phase inversion and hydrolysis process for cationic dye adsorption.The chemical structure and morphology of the composite adsorbents were systematically characterized by several characterization methods.Using methylene blue as the target dye,the influences of solution pH,contact time,initial dye concentration,and system temperature on the methylene blue adsorption process were investigated.The incorporation of Fe_(3)O_(4) particle into hydrolyzed polymers of intrinsic microporosity-1 endow the adsorbent with high magnetic saturation(20.7 emu·g^(–1))which allows the rapid separation of the adsorbent.Furthermore,the adsorption process was simulated by adsorption kinetics,isotherms and thermodynamics to gain insight onto the intrinsic adsorption mechanism.In addition,the composite adsorbents are able to selectively adsorb cationic dyes from mixed dyes solution.Hydrolyzed polymers of intrinsic microporosity/Fe_(3)O_(4) shows only a slight decrease for methylene blue adsorption after 10 adsorption/regeneration cycles,demonstrating the outstanding regeneration performance.The high adsorption capacity,outstanding regeneration ability,together with simple preparation method,endow the composite adsorbents great potential for selective removal of cationic dyes in wastewater system.

Separation/degradation behavior and mechanism for cationic/anionic dyes by Ag-functionalized Fe_(3)O_(4)-PDA core-shell adsorbents

High-performance adsorbents have been well-studied for the removal of organic dye pollutants to promote environment remediation.In this study,an Ag nanoparticle-functionalized Fe_(3)O_(4)-PDA nanocomposite adsorbent(PDA-Fe_(3)O_(4)-Ag)was synthesized,and the adsorption/separation performance of commonly used cationic and anionic organic dyes by the PDA-Fe_(3)O_(4)-Ag adsorbent were assessed.Overall,PDA-Fe_(3)O_(4)-Ag exhibited a significantly higher adsorption capacity for cationic dyes compared to anionic dyes,the highest of which was more than 110.0 mg/g(methylene blue(MB)),which was much higher than not only the adsorption capacities of the anionic dyes in this study but also other dye adsorption capacities reported in the literature.The dye adsorption kinetics data fitted well to both the pseudo second-order kinetics model and the Langmuir isotherm model,suggesting a monolayer-chemisorption-dominated adsorption mode.Thermodynamics analysis indicated that the adsorption process was both endothermic and spontaneous.Furthermore,the PDAFe_(3)O_(4)-Ag adsorbent achieved high photodegradation removal rates of the dyes,especially neutral red(NR)and methyl orange(MO),which were 91.2%and 87.5%,respectively.With the addition of PDA-Fe_(3)O_(4)-Ag,the degradation rate constants of NR and MO increased from 0.08×10^(−2)and 0 min^(−1)to 2.11×10^(−2)and 1.73×10^(−2)min−1,respectively.The high adsorption and photocatalytic degradation performance of the PDA-Fe_(3)O_(4)-Ag adsorbent make it an excellent candidate for removing cationic and anionic dyes from the industrial effluents.

Preparation of Fe-Mg MOFs and Its Application in Removal of RhB and MO

The world wide application of dyes in papermaking, fabric, lithography, leather and other industrial production, has attracted more attention, due to water pollution caused by these organic dyes. Metal-organic frameworks (MOFs) which are a physical adsorption method of wastewater treatment are a kind of special three-dimensional crystal-like constituents built by multipurpose ligands and metallic ion classes, showing an advantage in removal of pollutants from solutions because of its unique properties are convenient for operation, high removal efficiency, and low cost. In this study, we investigated Fe-Mg based metal organic framework, Fe-Mg MOFs which was directly synthesized by the hydrothermal method. The obtained materials were analyzed with XRD, FT-IR, TG-DTG, SEM etc. and used for the treatment of printing and dyeing wastewater. The results showed that it has good adsorption performance for cation dye rhodamine B (RhB) and anion dye methyl orange (MO) in a wide pH range. The Fe-Mg MOF even after the 4th run, the Fe-Mg MOF catalyst still maintained nearly the initial catalytic activities. The kinetic studies revealed the adsorption process of the both contaminants obeys a pseudo-second order model. In addition, the equilibrium adsorption data of RhB and MO are in good agreement with Langmuir models. The maximum adsorption capacities are 694.44 and 236.97 mg/g at 308 K respectively. This work synthesizes a promising dual-functional adsorbent that can remove cationic and anionic dyes, which provide potential applications for actual wastewater treatment.

A novel approach for Apocynum venetum/cotton blended fabrics modification by cationic polymer nanoparticles

Apocynum venetum/cotton blended fabrics have been subjected to treat with cationic polymer nanoparticles followed by dyeing with Acid Red B,and then studied for their dyeing performance and morphology.The investigation on the effect of modification factors on the blended fabrics indicated that the 0.5 g/L nanoparticles concentration,60 min treating time,60 ℃ treating temperature and pH 6-8 are the optimum modification process to improve the dyeability of acid dye.In addition,the SEM images show that nanoparticles can be adsorbed on the surface of modified A.venetum or cotton fibers,and the two different fibers could have the same adsorption ability to Acid Red B.

Preparation of MnO2 Loaded Hydrothermal Carbon-coated Electrospun PAN Fiber Membranes for Highly Efficient Adsorption and Separation of Cationic Dye

Hydrothermal carbonaceous materials and MnO2 have been proved to be promising adsorbents to remove organic dyes from wastewater.In this study,flexible MnO2 loaded hydrothermal carbon-coated electrospun poly-acrylonitrile(AC/MnO/PAN)fiber membranes were fabricated by a facile one-step hydrothermal method and activated by NaOH solution.The composite fibers exhibited large adsorption capacity toward cationic dyes and ex-cellent mechanical properties.The adsorption performance can be ftted well with pseudo-second order model and Langmuir isotherm model.The maximum adsorption for methylene blue(MB),methyI violet(MV)and malachite green(MG)are 1173.27,1106.31 and 1129.89 mg/g,respectively,according to Langmuir ftting.The AC/MnO/PAN fiber membrane also showed satisfactory performances for selective adsorption and recyclability.In addition,based on selective adsorption,the AC/MnOz/PAN fiber membranes that are repulsive to the anionic dye methyl orange(MO)can separate the MB/MO mixture solution by dynamic filration.Thus,this work not only provides a facile strategy to fabricate large capacity adsorbents,but also dermonstrates the potential appications in the dye wastewater treatment field.

Synthesis, characterization and assessment thermal properties of clay based nanopigments

Nano-clay based pigments （NCP） are new type of pigments composed of organic dyes and layered silicate- clay nano-particles, and have already been used in polymeric coatings to improve mechanical thermal and stability properties. In this paper, the basic blue 41（BB41） was intercalated into Na＋- montmorillonite in an aqueous medium. The dye-intercalated montmorillonite was cen- trifuged, dried, and milled to prepare the nanopigrnent particles. X-ray diffraction showed an increase in the basal spacing, thus confirming intercalation of the BB41 molecules within the nanostructures of the interlayer spaces. Fourier transform infrared spectroscopy was used for identifying the functional groups and chemical bounding of Na＋-montmorillonite, BB41 and montmor- illonite-BB41. The morphology of NCP was also studied by transmission electron microscopy. Finally, thermo- gravimetric analysis and differential thermograms sug- gested the thermal stability of the intercalated dye was improved.