Ultra-high specific surface area activated carbon from Taihu cyanobacteria via KOH activation for enhanced methylene blue adsorption

Cyanobacteria-based activated carbon(CBAC)was successfully prepared by pyrolysis-activation of Taihu cyanobacteria.When the impregnation ratio and activated temperature were 2 and 800-C,respectively,the optimal CBACs possessed an ultra-high specific surface(2178.90 m^(2)·g^(-1))and plenty of micro-and meso-pores,as well as a high pore volume(1.01 cm^(3)·g^(-1)).Ascribed to ultra-high surface area,π-π interaction,electrostatic interaction,as well as hydrogen-bonding interactions,the CBACs displayed huge superiority in efficient dye removal.The saturated methylene blue adsorption capacity by CBACs could be as high as 1143.4 mg·g^(-1),superior to that of other reported biomass-activated carbons.The adsorption was endothermic and modeled well by the pseudo-second-order kinetic,intra-particle diffusion,and Langmuir models.This work presented the effectiveness of Taihu cyanobacteria adsorbent ascribed to its super large specific surface area and high adsorption ability.

Adsorption characteristics of humic acid-immobilized amine modified polyacrylamide/bentonite composite for cationic dyes in aqueous solutions

Humic acid-immobilized amine modified polyacrylamide/bentonite composite （HA-Am-PAA-B） was prepared and used as an adsorbent for the adsorption of cationic dyes （Malachite Green （MG）, Methylene Blue （MB） and Crystal Violet （CV）） from aqueous solutions. The polyacrylamide/bentonite composite （PAA-B） was prepared by intercalative polymerization of acrylamide with Nabentonite in the presence of N,N＇-methylenebisacrylamide as a crosslinking agent and hexamethylenediammine as propagater. PAA-B was subsequently treated with ethylenediammine to increase its loading capacity for HA. The surface characterizations of the adsorbent were investigated. The adsorbent behaved like a cation exchanger and more than 99.0% removal of dyes was detected at pH range 6.0-8.0. The capacity of HA-Am-PAA-B was found to decrease in the following order： MG〉MB〉CV. The kinetic and isotherm data were interpreted by pseudo-second order rate equation and Freundlich isotherm model, respectively. Experiments were carried out using binary solute systems to assess the competitive adsorption phenomenon. The experimental isotherm data for each binary solute combination of MG, MB and CV were analyzed using Sheindrof-Rebhun-Sheintuch （SRS） （multicomponent Freundlich type） equation.

High surface area and mesoporous activated carbon from KOH-activated dragon fruit peels for methylene blue dye adsorption:Optimization and mechanism study

In this study,an alternative precursor for production of activated carbon was introduced using dragon fruit(Hylocereus costaricensis)peel(DFP).Moreover,KOH was used as a chemical activator in the thermal carbonization process to convert DFP into activated carbon(DFPAC).In order to accomplish this research,several approaches were employed to examine the elemental composition,surface properties,amorphous and crystalline nature,essential active group,and surface morphology of the DFPAC.The BrunauerEmmettTeller test demonstrated a mesoporous structure of the DFPAC has a high surface area of 756.3 m2g 1.The cationic dye Methylene Blue(MB)was used as a probe to assess the efficiency of DFPAC towards the removal of MB dye from aqueous solution.The effects of adsorption input factors(e.g.DFPAC dose(A:0.040.12 g L 1),pH(B:310),and temperature(C:3050℃))were investigated and optimized using statistical analysis(i.e.BoxBehnken design(BBD)).The adsorption kinetic model can be best categorized as the pseudofirst order(PFO).Whereas,the adsorption isotherm model can be best described by Langmuir model,with maximum adsorption capacity of DFPAC for MB dye was 195.2 mg g 1 at 50℃.The adsorption mechanism of MB by DFPAC surface was attributed to the electrostatic interaction,pp interaction,and Hbonding.Finally,the results support the ability of DFP to be a promising precursor for production of highly porous activated carbon suitable for removal of cationic dyes(e.g.MB).

Synthesis and characterization of carboxymethyl cellulose/organic montmorillonite nanocomposites and its adsorption behavior for Congo Red dye

A series of carboxymethyl cellulose/organic montmorillonite （CMC/OMMT） nanocomposites with different weight ratios of carboxymethyl cellulose （CMC） to organic montmorillonite （OMMT） were synthesized under different conditions. The nanocomposites were characterized by the Fourier transform infrared （FT-IR） spectrophotometer, X-ray diffraction （XRD） method, transmission electron microscope （TEM）, scanning electron microscope （SEM）, and thermal gravimetric （TG） analysis. The results showed that the introduction of CMC may have different influences on the physico-chemical properties of OMMT and intercalated-exfoliated nanostructures were formed in the nanocomposites. The effects of different reaction conditions on the adsorption capacity of samples for Congo Red （CR） dye were investigated by controlling the amount ofhexadecyl trimethyl ammonium bromide （CTAB）, the weight ratio of CMC to OMMT, the reaction time, and the reaction temperature. Results from the adsorption experiment showed that the adsorption capacity of the nanocomposites can reach 171.37 rag/g, with the amount of CTAB being 1.0 cation exchange capacity （CEC） of MMT, the weight ratio of CMC to OMMT being l：l, the reaction time being 6 h, and the reaction temperature being 60~C. The CMC/OMMT nanocomposite can be used as a potential adsorbent to remove CR dye from an aqueous solution.

Photo-Grafting Copolymerization of PP Nonwoven Fabric and Its Application for Acidic Dye Adsorption and Filtration

The monomer methacrylamido propyl trimethy ammonium chloride( MAPTAC) was copolymerized onto the fiber surface of polypropylene( PP) nonwoven fabric under ultroviole radiation. The weak acid red GN dye adsorption and adsorptive filtration performance of the resulted PP fabrics were investigated.The results showed that the grafting copolymerization preferred to happen in the inner layer of the fabrics. The water flux of the grafted fabrics decreases with the increase of grafting yield. The collapse of the grafted polymer chains causes the flux increase in acidic condition,or vice versa at alkaline version. The coiling of the polyelectrolyte chains upon the dye adsorption seems to violate the routine assumption of the rigid substrate, and this gets the adsorption energy constant negative. The static adsorption process follows the Lagergren's pseudo-second order kinetic equation. The removals of circa( ca.) 100% of the total permeation volume3 500 mL simulated dye wastewater was reached during permeation.The dye adsorbed fabrics were regenerated by the mixed media of the cationic surfactant / ethanol /water. The grafted fabric assumes stable fabric integrity and stability during permeation,and presents excellent dye adsorption capacity,easy desorption, and repeatable utilization.

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.

Adsorption of Methylene Blue on magnesium silicate: Kinetics, equilibria and comparison with other adsorbents

Batch adsorption from aqueous solutions in a slightly basic medium of Methylene Blue, up to 2500 mg/L, onto synthetic magnesium silicate （Florisil） of three particle size ranges （mean diameters of 112, 200 and 425 μm） was compared to the corresponding adsorption onto activated carbon and Amberlite XAD-2. The best fit of the kinetic results was achieved by a pseudo second-order equation. The equilibrium data were found to be well represented by the Langmuir isotherm equation. Amberlite XAD-2, an unspecific adsorbent capable of adsorbing exclusively through a surface effect, exhibited a poor dye uptake, confirming that the adsorption mechanism on Florisil was due to electrostatic attraction and ion exchange. Moreover, the comparison between Florisil and the other adsorbents was performed on the basis of the evaluation of the surface area and pore volume occupied by the adsorbed dye.

Preparation and Properties of Polyacrylamide/Sodium Alginate Hydrogel and the Effect of Fe^(3+)Adsorption on Its Mechanical Performance

The preparation and application of functional hydrogels based on natural polysaccharides have always been a hot research topic.In this study,using acrylamide(AM)monomer,N,N'-methylene bisacrylamide(MBA)as crosslinking agent,potassium persulfate(K2S2O8)as initiator,in the presence of natural polysaccharide sodium alginate(SA),the PAM/SA hydrogel was prepared by free radical polymerization.Fourier transform infrared spectroscopy(FT-IR),swelling performance tests,scanning electron microscope(SEM),thermogravimetric analysis(TGA),UV-visible spectrophotometer,mechanical property measurements were carried out to analyze the composition,morphology,and performance of the hydrogels.The swelling behavior,dye adsorption performance,and the mechanical properties of PAM/SA hydrogels before and after Fe^(3+)adsorption were studied.The experimental results showed that the introduction of SA with 4.7%,7.8%,and 10.3%effectively improved the mechanical and dye adsorption properties of PAM composite hydrogels.The adsorption capacity of PAM/4.7%SA and PAM/10.3%SA hydrogels at equilibrium can reach 40.01 and 44.02 mg/g for methylene blue,which is higher than the value 13.58 mg/g of pure PAM hydrogel.The compressive strength of pure PAM hydrogel is 0.124 MPa.When the SA content is 4.7%,7.8%,and 10.3%,the compressive strength of the PAM/SA hydrogel was corresponding to 0.130 MPa,0.134 MPa,and 0.152 MPa,respectively.Fe^(3+)was introduced into the PAM/SA hydrogels,and PAM/SA/Fe^(3+)double-network hydrogels with excellent mechanical properties could be prepared by adjusting the SA content(4.7%,7.8%,and 10.3%),soaking time(1 h,2 h,3 h,4 h,5 h,6 h),and Fe^(3+)concentration(4.76%,7.41%,9.09%,and 13.04%).Under the same Fe^(3+)concentration of 9.09%and adsorption time of 4 h,the compressive strengths of the PAM/4.7%SA,PAM/7.8%SA,and PAM/10.3%SA hydrogels could reach 0.354 MPa,0.767 MPa,and 0.778 MPa,respectively.

Synthesis of activated carbons from black sapote seeds,characterization and application in the elimination of heavy metals and textile dyes

Many different techniques may be used to remove industrial pollutants from wastewater. Adsorption using activated carbon has been reported to be an effective method. This work proposes the use of a vegetable residue(black sapote seeds) as a raw material for its synthesis. These carbons were chemically activated using phosphoric acid and carbonized at 673 and 873 K. Adsorption isotherms were constructed for the textile dyes on the carbons, and this data was treated using Langmuir’s equation to quantitatively describe the adsorption process. The synthesized carbons were characterized using FTIR, EA, SEM, Nitrogen adsorption(specific surface areas of 879 and 652 m2·g-1), and their points of zero charge(2.1 and 2.3). It was possible to adsorb both heavy metals and textile dyes present in aqueous solutions and wastewaters using these activated carbons. Heavy metals were adsorbed almost completely by both carbons. Cationic dyes where adsorbed(58–59.8 mg·g-1) in greater amounts compared to anionic dyes(10–58.8 mg·g-1). The amount of anionic dyes adsorbed increased almost 30% by changing the pH of the solutions. One of the carbons was thermally regenerated on three occasions without losing its adsorption capacity and it was proved in a flow system.

Applicable models for multi-component adsorption of dyes:A review

Adsorption is one of the several techniques that has been successfully used for dyes removal.Since most industrial colored effluents contain several components including dyes,having a strong knowledge about the scope of competitive adsorption process is a powerful key to design an appropriate system.This is mainly because of the complexity brought about by the increasing number of parameters needed for process description which complicates not only the process modeling but also the experimental data collection.A multicomponent adsorption model should be based on fundamental soundness,speed,and simplicity of calculation.For such systems,competition will change the adsorbent-adsorbate attractions.Thus,there is major concern to develop an accurate and reliable method to predict dye adsorption behavior in multi-component systems.This article covers topics such as the theory of dyes adsorption in multi-component systems along with applicable models according to the consistent theories presented by researchers.

Superabsorbent amphoteric nanohydrogels: Synthesis,characterization and dyes adsorption studies

The goal of the present research is to remove high percentage of cationic and anionic dyes such as,Neutral Red, Safranin O and Indigo Carmine from aqueous solutions by poly（NIPAAm/N,Ndiallylpyrrolidinium bromide/AA） superabsorbent amphoteric nanohydrogels synthesized using the inverse microemulsion polymerization method. Effect of various parameters such as, treatment time,initial dye concentration, p H and adsorbent dose were investigated. Furthermore, kinetics and isotherms adsorption models were applied to determine the maximum adsorption and mechanism for adsorption,which shows that adsorption obeyed the pseudo-second order kinetics. From the results, removal of dyes within the nanohydrogel was found to be in the order： AB-74 〈 BR-2≤ BR-5.

Tough Poly(L-DOPA)-containing Double Network Hydrogel Beads with High Capacity of Dye Adsorption

Developing a low-cost and well-recyclable adsorbent with high adsorption capacity is greatly desirable in dye wastewater treatment. Here, we demonstrate a kind of novel tough and reusable hydrogel beads with quite high capacity of dye adsorption via incorporating mussel-bioinspired poly（L-DOPA） （PDOPA） into alginate/poly（acrylamide） double network （DN） hydrogels. The synthesized PDOPA nanoaggregates were introduced into the DN hydrogels by simple one-pot mixing with the monomers prior to polymerization. The fabricated hydrogel beads exhibited high mechanical strength and good elastic recovery due to the interpenetrating Ca2＋-alginate and poly（acrylamide） networks. It was shown that the beads exhibited relatively high dye adsorption capacity compared to other adsorbents reported in literature, and the introduction of PDOPA with an appropriate amount raised the adsorption capacity. It is believed that the addition of PDOPA and the matrix of double network architecture contributed synergistically to the high adsorption capacity of hydrogel beads. Moreover, the desorption of dyes could be easily realized via rinsing in acidic water and ethanol solution. The hydrogel beads remained the high adsorption capacity even after 5 times of adsorption and desorption cycles. This tough and stable hydrogel with high adsorption capacity may have potential in treatment of dye wastewater released by textile dyeing industry.

Sulfonated Hollow Covalent Organic Polymer： Highly-Selective Adsorption toward Cationic Organic Dyes over Anionic Ones in Aqueous Solution

A sulfonated hollow covalent organic polymer （sh-COP-P） was prepared by post sulfonation of hollow covalent organic polymer （h-COP-P） synthesized through poly-condensation of tetrabiphenylporphyrin （TBPP）. In comparison with h-COP-P, sh-COP-P exhibits significantly enhanced adsorp- tion capacity of organic cationic dyes in aqueous solutions accompanied with notably reduced adsorption capacity of anionic dyes. This gives sh-COP-P a satisfactory performance in selectively separating cationic organic dyes from anionic ones, mainly attributed to the electrostatic interaction between polymer backbone and the guest molecules.

Single and Binary Dye Adsorption of Methylene Blue and Methyl Orange in Alcohol Aqueous Solution via Rice Husk Based Activated Carbon:Kinetics and Equilibrium Studies

The present work was mainly focused on the single and binary adsorption of methylene blue(MB)and methyl orange(MO)from alcohol aqueous solution over rice husk based activated carbon(RHAC).The study of single dye adsorption equilibrium experiments found that the Langmuir adsorption model was consistent with the adsorption behavior of RHAC on MB and MO,indicating that it was a single layer adsorption.The adsorption behavior con-formed to the pscudo-second-order kinetic model.The binary dye adsorption experiments showed that the Lang-muir-Freundlich model could be applied to describe the adsorption behavior of RHAC on MB and MO.Comparation with the single dye system,the adsorption capacity on the binary dye system was larger,and there was"competitive adsorption"and"synergistic adsorption"effects existed.Meanwhile,the pseudo-second-order kinetic model also fit for the binary dye adsorption behavior.

A Multifunctional {P_(2)Mo_(5)}-based Hybrid Applying to Catalysis, Electrocatalysis and Dye Adsorption

As a common environmental pollutant, thioether can cause serious environmental pollution, so selective oxidation of thioether has become one of the current research hotspots. In this paper, an inorganic-organic hybrid based on a Standberg-type polyoxometalate, [Hbiz]_(5)[HP_(2)Mo_(5)O_(23)]·5H_(2)O(1)(biz=benzimidazole), was obtained by adjusting pH under hydrothermal conditions. The structure was characterized by infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Compound 1 can be used as an excellent catalyst for the oxidation of thioanisole. The experimental results showed that thioanisole could be catalytically oxidized to methyl phenyl sulfoxide by compound 1 as a catalyst within 40 min. The conversion rate and selectivity reached 99%. Compound 1 had good cycling stability as a heterogeneous catalyst. In addition, the electrocatalytic reduction of H_(2)O_(2) and Cr_(2)O_(7)^(2−) for hybrid 1 was preliminarily investigated. In addition, the adsorption performance of hybrid 1 on cationic dye crystal violet and methylene blue was tested, and the adsorption efficiencies can reach 98.5% and 86.3%, respectively.

A Three-dimensional Covalent Organic Framework for CO_(2) Uptake and Dyes Adsorption

Environmental pollution is one of the most severe problems facing today,including water pollution and the greenhouse effect.Therefore,developing materials with high-efficiency dyes adsorption and CO_(2)uptake is significant.Covalent organic frameworks(COFs),as a burgeoning class of crystalline porous polymers,present a promising application potential in areas related to pollution regulation due to their exciting surface properties.Herein,we report a 3D COF with a high specific surface area(BET about 2072 m^(2)/g)by utilizing tetrahedral and rectangle building blocks connected through[4+4]imine condensation reactions to synthesize.The obtained COF not only can separate dyes from water effectively but also shows a remarkable CO_(2)uptake capacity.This research thus provides a promising material to remove dyes and adsorb CO_(2)in environmental remediation.

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.

Thiacalix[4]arene 1,2,3-triazole-polyethylene glycol polymers:Synthesis and dye adsorption properties

By reacting alkynylthiacalix[4]arenes with polyethylene glycol azido compounds,a series of novel thiacalix[4]arene 1,2,3-triazole-polyethylene glycol netty polymers were conveniently prepared in good yields.Their structures and morphologies were studied by ^1H NMR,IR.and elemental analysis and SEM images.On average,approximately 28-31 thiacalixarene units exist in each polymeric molecule.These novel polymers possess excellent adsorption ability for both cationic and anionic dyes.The saturation adsorption capacity for Congo red reached 1.3-1.4 mmol/g.They exhibit high and stable adsorption ability in the scope of pH 5-9,and maintain good properties in five cycles.

Rapid formation of metal-monophenolic networks on polymer membranes for oil/water separation and dye adsorption

Surface deposition based on metal-phenolic networks(MPNs) has received increasing interest in recent years. The catechol structure is generally considered to be essential to the formation of MPNs. Our most recent results have demonstrated that some kinds of monophenols can form MPNs on substrate surfaces.Herein, we report a fast and effective surface-coating system based on the coordination of 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid, a kind of monophenol, with Fe^(3+). Compared with other metal ions such as Cu^(2+)and Ni^(2+), Fe^(3+)with stronger electron acceptability can coordinate with the monophenol more strongly to form MPNs, and moreover, the deposition time significantly decreases to 40 min from generally 24 h. It is demonstrated that the deposition process is controlled by the coordination, Fe^(3+)hydrolysis, and deprotonation of the monophenol. The coatings endow substrates such as polypropylene microfiltration membrane with underwater superoleophobicity, which can be applied in oil/water separation with high separation efficiency and great long-term stability. In addition, the coated membranes are positively charged and thus are useful in selective adsorption of dyes. The present work not only provides a novel, fast, and one-step deposition method to fabricate MPNs, but also demonstrates that the fabrication efficiency of monophenol-based MPNs is comparable with that of polyphenol-based MPNs.

Solvent-tuned polyoxometalate-based supramolecular hybrids constructed from different metal-organic motifs:Various structures and adsorption properties for dyes

By changing the solvents, three polyoxometalate（POM）-based supramolecular hybrids, [Co2 L3][SiW（12）O（40）]·17 H2 O（1）,[Co2 L2（H2 O）4][SiW（12）O（40）].2 EtOH·2 H2 O（2） and [Co2 L3][SiW（12）O（40）]·9 DMA·6 H2 O（3）, have been synthesized under hydrothermal or solvothermal conditions. All three hybrids show various supramolecular structures, which contain two kinds of different metal-organic motifs. A kind of metal-organic cationic cage [Co2 L3]^4＋ is formed in the presence of H2 O for 1, DMA/H2 O for 3, and a metalorganic cationic circle [Co2 L2]^（4＋） is constructed in the presence of EtOH/H2 O for 2. That is to say, the solvents show a key role in tuning the architectures of metal-organic fragments and the final POM-based supramolecular structures. The adsorption properties of 1-3 for different organic dyes have also been investigated.