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”.

Suppress oxygen evolution of lithium-rich manganese-based cathode materials via an integrated strategy

Improving the reversibility of anionic redox and inhibiting irreversible oxygen evolution are the main challenges in the application of high reversible capacity Li-rich Mn-based cathode materials.A facile synchronous lithiation strategy combining the advantages of yttrium doping and LiYO_(2) surface coating is proposed.Yttrium doping effectively suppresses the oxygen evolution during the delithiation process by increasing the energy barrier of oxygen evolution reaction through strong Y–O bond energy.LiYO_(2) nanocoating has the function of structural constraint and protection,that protecting the lattice oxygen exposed to the surface,thus avoiding irreversible oxidation.As an Li^(+) conductor,LiYO_(2) nano-coating can provide a fast Li^(+) transfer channel,which enables the sample to have excellent rate performance.The synergistic effect of Y doping and nano-LiYO_(2) coating integration suppresses the oxygen release from the surface,accelerates the diffusion of Li^(+)from electrolyte to electrode and decreases the interfacial side reactions,enabling the lithium ion batteries to obtain good electrochemical performance.The lithium-ion full cell employing the Y-1 sample(cathode)and commercial graphite(anode)exhibit an excellent specific energy density of 442.9 Wh kg^(-1) at a current density of 0.1C,with very stable safety performance,which can be used in a wide temperature range(60 to-15℃)stable operation.This result illustrates a new integration strategy for advanced cathode materials to achieve high specific energy density.

Modeling of the Adsorption Allowing for the Changing Adsorbent Activity at Various Stages of the Process

The goal of this work is,first of all,to construct a mathematical model of the mass transfer process in porous adsorption layers,taking into account the fact that in most cases the adsorption process is carried out in nonstationary technological modes,which requires a clear description of its various stages.The scientific contribution of the novel model is based on a probability approach allowing for deriving a differential equation that takes into account the diffusion migration of adsorbed particles.Solving this equation allows us to calculate the reduced degree of the adsorption surface coverage along the flow and,thereby,calculate the efficiency of the mass transfer process.The model also makes it possible to determine the slip coefficient,the internal diffusion coefficient and the degree of filling of the internal surface of the pores of the adsorbent layer,which corresponds to the completion of the initial stage of adsorption and the transition of the process to a stable mode.In this case,the problem is to calculate a non-isothermal turbulent boundary layer when flowing around the surface of an adsorbent.Next,the problem of identifying the main control parameters of the model has been solved.Based on such analysis and experimental studies to assess the influence of process control parameters,the patterns of adsorption purification and solution separation have been established and the design of a highly efficient adsorption apparatus with a fixed layer of porous adsorbent have been developed.

Synthesis of Li^+ adsorbent(H_2TiO_3) and its adsorption properties

H2TiO3 was obtained from the acid-modified adsorbent precursor Li2TiO3,which was synthesized by a solid-phase reaction between TiO2 and Li2CO3.The extraction ratio of Li＋ from Li2TiO3 was 98.86%,almost with no Ti4＋ extracted.The effects of lithium titanium ratio,calcining temperature and time were investigated on the synthesis of Li2TiO3.Li2TiO3,H2TiO3 and the adsorbed Li＋ adsorbent were characterized by XRD and SEM.The lithium adsorption properties were investigated by the adsorption kinetics and adsorption isotherm.The results indicate that H2TiO3 has an excellent adsorptive capacity for Li＋.Two simplified kinetic models including the pseudo-first-order and pseudo-second-order equations were selected to follow the adsorption processes.The rate constants of adsorption for these kinetic models were calculated.The results show that the adsorption process can be described by the pseudo-second-order equation,and the process is proved to be a chemical adsorption.The adsorption process that H2TiO3 adsorbs Li＋ in LiCl solution well fits the Langmuir equation with monolayer adsorption.

Properties of Advanced Adsorbent for Solid Desiccant Cooling

Characteristics of 13x molecular sieve, silica gel and DH 5 and DH 7 prepared by authors, were investigated for the solid desiccant cooling system. The adsorption isotherms of DH 5 and DH 7 were experimentally determined. The performance parameters of adsorption capacity, air humidity, regeneration temperature and cooling volume were tested and discussed in detail. The results show that the properties of new adsorbents DH 5 and DH 7 on desiccant cooling are much better than those of common desiccants. The maximum adsorption volumes of water on DH 5 and DH 7 are 0.72?kg/kg and 0.73 ?kg/kg, respectively. The desiccant cooling volumes of DH 7and DH 5 are 2.2 and 1.3 times larger than those of silica gel and 13x(molecular sieve), respectively, after regeneration at 100?℃. The cooling volume per mass unit of DH 5 is 1.9 times larger that of 13x.

Adsorption/desorption behavior between a novel amphoteric granular lignin adsorbent and reactive red K-3B in aqueous solutions

A novel amphoteric granular lignin adsorbent(AGLA) was prepared using magnesium lignosulfonate as a raw material which was provided by a straw sulfite pulp mill in Guangdong Province, China. A reactive dye(red K-3B) was used as an adsorbate to investigate the adsorption behavior by static and mobile ways. The removal of reactive red K-3B was found to be initially pH and concentration dependent. Moreover, an increase of solution temperature ranging from 5℃ to 60℃ helped to enhance the rate of intraparticle diffusion of adsorbate and changes in the size of the pores of the adsorbent and thus to reduce the adsorption time. The total breakthrough adsorption capacity was 531 mg/g, and the saturated adsorption capacity was 560 mg/g, which prevailed over the activated carbons evidently. The reactive red K-3B adsorbed on AGLA could be recovered with a mixture of alcohol, NaCl and HCl aqueous solutions. The recovery percentage could reach 92.4%.

Effect of pyrolysis temperature and hold time on the characteristic parameters of adsorbent derived from sewage sludge

According to the Doehlert's matrix method, the adsorbent derived from sewage sludge was prepared through chemical activation under controlling the pyrolysis temperature and hold time. The characteristic parameters including the total yield, adsorption of methylene blue, adsorption of iodine, BET surface area, micro-pore volume are 35%—49%, 16.5—38 mg/g, 285—362 mg/g, 185—359 m2/g, and 0.112—0.224 m3/g, respectively. According to the experimental data, the multi-linear regression method was adopted to fit the relations between the characteristic parameters and influential factors. At final, through optimization method, the optimal adsorbent is obtained when using 62 min as hold time and 1105K as pyrolysis temperature. Under the conditions, the adsorbent was produced and compared the characteristic parameters with model forecast value, the coherence is satisfied.

Hexagonal boron nitride adsorbent: Synthesis, performance tailoring and applications

Hexagonal boron nitride(h-BN),with unique structural and properties,has shown enormous potentitoward variety of possible applications.By virtue of partially-ionic character of BN chemical bonds anusually large specific surface area,h-BN-related nanostructures exhibit appealing adsorption propertiewhich can be widely applied for separation and purification towards energy and environment treatmenIn this review,recent progress in designing h-BN micro,nano-structure,controlled synthesis,performancoptimizing as well as energy and environment-related adsorption applications are summarized.Strategieto tailor the h-BN can be classified as morphology control,element doping,defect control and surfacmodification,focusing on how to optimize the adsorption performance.In order to insight the intrinsimechanism of tuning strategies for property optimization,the significant adsorption applications of h-Btowards hydrogen storage,CO2 capture,pollutants removal from water and adsorption desulfurization arpresented.

Organobentonites as adsorbents for some organic pollutants and its application in wastewater treatment

Two organobentonites were synthesized by placing quaternary ammonium cationscetyltrimethylammonium bromide (CTMAB) and cetylpyridinium chloride (CPC) on bentonite bycation exchange. Their ability to adsorb phenol, aniline. nitrobenzene and p-nitrophenol were examined.The optimal conditions for organobentonites to remove the organic pollutants from waterwere studied. The removal rates for organobentonites to treat the organic compounds in water werefound to be over 8 times for the original mineral (untreated bentonite).The removal rates of organic pollutants and COD of wastewater were further improved by organobentonites in the presence of aluminum sulfate. The structure of organobentonites and the mechanism for their adsorption were investigated by X-ray diffraction (XRD) analysis, infrared spectra and BET surface area.

RhB Adsorption Performance of Magnetic Adsorbent Fe_3O_4/RGO Composite and Its Regeneration through A Fenton-like Reaction

Adsorption is one of the most effective technologies in the treatment of colored matter containing wastewater. Graphene related composites display potential to be an effective adsorbent. However, the adsorption mechanism and their regeneration approach are still demanding more efforts. An effective magnetically separable absorbent, Fe3O4 and reduced graphene oxide(RGO) composite has been prepared by an in situ coprecipitation and reduction method. According to the characterizations of TEM, XRD, XPS, Raman spectra and BET analyses, Fe3O4 nanoparticles in sizes of 10-20 nm are well dispersed over the RGO nanosheets, resulting in a highest specific area of 296.2 m2/g. The rhodamine B adsorption mechanism on the composites was investigated by the adsorption kinetics and isotherms. The isotherms are fitting better by Langmuir model, and the adsorption kinetic rates depend much on the chemical components of RGO. Compared to active carbon, the composite shows 3.7 times higher adsorption capacity and thirty times faster adsorption rates. Furthermore,with Fe3O4 nanoparticles as the in situ catalysts, the adsorption performance of composites can be restored by carrying out a Fenton-like reaction, which could be a promising regeneration way for the adsorbents in the organic pollutant removal of wastewater.

Recent developments and consideration issues in solid adsorbents for CO_2 capture from flue gas

The increase in energy demand caused by industrialization leads to abundant CO_2 emissions into atmosphere and induces abrupt rise in earth temperature. It is vital to acquire relatively simple and cost-effective technologies to separate CO_2 from the flue gas and reduce its environmental impact. Solid adsorption is now considered an economic and least interfering way to capture CO_2, in that it can accomplish the goal of small energy penalty and few modifications to power plants. In this regard, we attempt to review the CO_2 adsorption performances of several types of solid adsorbents, including zeolites, clays, activated carbons, alkali metal oxides and carbonates, silica materials, metal–organic frameworks, covalent organic frameworks, and polymerized high internal phase emulsions. These solid adsorbents have been assessed in their CO_2 adsorption capacities along with other important parameters including adsorption kinetics, effect of water, recycling stability and regenerability. In particular,the superior properties of adsorbents enhanced by impregnating or grafting amine groups have been discussed for developing applicable candidates for industrial CO_2 capture.

Synthesis and characterization of porous 4VP-based adsorbent for Re adsorption as analogue to 99Tc

Technetium(^(99)Tc), a major fission product in nuclear reactors, of high yield, long-half-life and high mobility in the environment must be removed in nuclear fuel reprocessing. Considering rhenium(Re) and Tc are both VIIB elements, Re is a good chemical analogue to ^(99)Tc. Herein, we use Re as a substitution of ^(99)Tc to study adsorption and desorption behavior. Porous 4-vinylpyridine–divinylbenzene-based(4VP–DVB) adsorbent containing tertiary amine groups is synthesized by suspension polymerization and characterized by BET, TGA, SEM and laser particle size analyzer. The adsorbent has high adsorption efficiency toward Re(VII) in 0.1 mol/L nitric acid solution, and the adsorption equilibrium can be achieved in 30 min. The adsorption kinetics of Re(VII)follows pseudo-second-order rate equation, the adsorption isotherm matches well with the Langmuir isotherm, and the adsorption capacity of Re(VII) on 4VP–DVB adsorbent is 352.1 mg/g at 298 K. Thermodynamic study reveals that the adsorption process is exothermic. This adsorbent is of separation convenience when a fixed-bed column is used,compared to the batch adsorption treatment.

Dye removal from wastewater using the adsorbent developed from sewage sludge

Sewage sludge was used to develop an effective carbon adsorbent. This adsorbent was employed for the removal of azo dye such as Direct Dark Brown M and Acid Mordant Brown RH. The adsorption of dyes on this adsorbent was studied as a function of contact time, concentration, pH and temperature by batch method. The equilibrium adsorption capacity of a carbonaceous adsorbent prepared from city wastewater treatment plant was 502, and 329.7 mg/g of Direct Dark Brown M and Acid Mordant Brown RH, respectively. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model. The rates of adsorption were found to conform to the Lagergren second-order kinetics with good correlation. The equilibrium adsorption capacity of the carbonaceous adsorbents was determined with the Langmuir equation as well as the Lagergren second-order rate equation. The most ideal pH for adsorption of two dyes onto adsorbents was found to be 3 and below. The results indicate that the carbonaceous adsorbents could be employed as a low cost adsorbent in the removal of dyes from wastewater.

Graphene oxide based carbon composite as adsorbent for Hg removal:Preparation, characterization, kinetics and isotherm studies

The presence of Hg in the aqueous media is known to cause severe health issues in both humans and animals.Many technologies and especially adsorbents have been applied for its removal. In this study, a graphene oxide–carbon composite(GO–CC) as a new adsorbent was prepared by sol gel procedure and characterized using field emission scanning electron microscopy, BET and EDX. The effects of different variables including solution p H, contact time, adsorbent dose and GO ratio in adsorbent matrix on the removal capacity of Hg were studied. The isotherm data correlated well with the Langmuir isotherm model. Further analysis recommended that the Hg^(2+) adsorption process is governed by the intra-particle and external mass transfer, in which the film diffusion was the rate restrictive step. The presented composite has maximum absorption capacity, q_(max) of 68.8 mg·g^(-1), which is comparable with carbon based adsorbent reported in the previous publications.

Recyclable adsorbent of BiFeO_3/Carbon for purifying industrial dye wastewater via photocatalytic reproducible

It is essential to prepare highly-efficiency reproducible adsorbent for purifying industrial dye wastewater. In this work, biscuit with a layered porous structure as a template is applied to prepare a photocatalytic recyclable adsorbent of BiFeO3/Carbon nanocomposites for purifying simulative industrial dye wastewater. It is found that the structure of the prepared BiFeO3/Carbon nanocomposite is related to the natural structure of the biscuit, annealing temperatures and immersing times, demonstrated by XRD, TEM, UV-Vis and adsorptive activities. Kinetics data shows that the adsorption rate of the adsorbent to the dye is rapid and fitted well with the pseudo-second-order model, that more than 80% of dyes can be removed in the beginning 30 min. The adsorption isotherm can be perfectly described by the Langmuir model as well. It can be seen from the adsorption data that the adsorption performance can reach over 90% at pH ? 2–12, which can imply its universal utilization. The prepared BiFeO_3/Carbon nanocomposites have also displayed excellent capacities(over 90% within 30 min) for adsorption of seven different dyes and their mixed one. According to the five times photocatalytic reproducible experiments, it is proved that BiFeO_3/Carbon nanocomposites show the excellent stability and reproduction for purifying simulative industrial dyes, even the sample have been placed for one year. These research results indicate that the adsorbent BiFeO_3/Carbon can be a suitable material used in treating industrial dye wastewater potentially.

Highly Selective Lithium Ion Adsorbents:Polymeric Porous Microsphere with Crown Ether Groups

In this study, we prepared and applied polymeric porous microsphere adsorbents with selectivity for Li^+ extraction from aqueous solution. We synthesized the adsorbents by suspension polymerization using methacryloyoxyme-12-crown-4(M12C4) as a functional monomer, which had been synthesized from 2-hyroxymethyl-12-crown-4 and methacryloyl chloride. We verified the chemical composition by solid nuclear magnetic resonance(13C-NMR) spectroscopy and observed the porous structure by scanning electron microscopy(SEM). We conducted adsorption isothermal and kinetic tests to determine the adsorption properties. It was found that the adsorbents showed high adsorption efficiency and an adsorption equilibrium time of 200 min. In addition, since the crown ether used in this work could form a stable complex with Li^+, we observed good selectivity for Li^+ in the prepared solution compared with other ions such as Na^+, K^+, Mg^(2+), and Ca^(2+). We reused the adsorbents five times with no significant decrease in adsorptive capacity.

Binary competitive adsorption of naphthalene compounds onto an aminated hypercrosslinked macroporous polymeric adsorbent

An aminated hypercrosslinked macroporous polymeric adsorbent was synthesized and characterized. Adsorption isotherms for 1 amino 2 naphthol 4 sulfonic acid(1, 2, 4 acid) and 2 naphthol obtained from various binary adsorption environments can be well fitted by Freundlich equation, which indicated a favorable adsorption process in the studied range. Adsorption for 1, 2, 4 acid was an endothermic process in comparison with that for 2 naphthol of an exothermic process. 2 naphthol molecules put a little influence on the adsorption capacity for 1, 2, 4 acid. However, the adsorption to 1, 2, 4 acid depressed that to 2 naphthol in a large extent for the stronger electrostatic interaction between 1, 2, 4 acid and adsorbent. The predominant mechanism can be contributed to the competition for adsorption sites. And the simultaneous environment was confirmed to be helpful to the selective adsorption towards 1,2,4 acid based on the larger selectivity index.

Adsorption thermodynamics and kinetic investigation of aromatic amphoteric compounds onto different polymeric adsorbents

The adsorption behavior ofp-aminobenzoic acid and o-aminobenzoic acid onto the different polymeric adsorbents was systematically investigated as a function of the solution concentration and temperature. Experimental results indicated that the equilibrium adsorption data of the four polymeric adsorbents fitted well in the Freundlich isotherm. The adsorption capacity of multi-functional polymeric adsorbent NJ-99 was the highest, which might be attributed to the strong hydrogen-bonding interaction between the amino groups on the resin and the carboxyl group of aminobenzoic acid. The adsorption capacity of o-aminobenzoic acid onto any adsorbent was higher than p-aminobenzoic acid. Thermodynamic studies suggested the exothermic, spontaneous physical adsorption process. Adsorption kinetics results showed that the adsorption followed the pseudo-second-order kinetics model and the intraparticle mass transfer process was the rate-controlling step.

Thermodynamic study of adsorption of phenolic compounds onto Amberlite XAD-4 polymeric adsorbents and its acetylized derivative MX-4

Adsorption equilibrium isotherms of phenolic compounds, phenol, p cresol, p chlorophenol and p nitrophenol, from aqueous solutions by Amberlite XAD 4 polymeric adsorbent and its acetylized derivative MX 4 within temperature range of 283 323K were obtained and fitted to the Freundlich isotherms. The capacities of equilibrium adsorption for all four phenolic compounds from their aqueous solutions increased around 20% on the acetylized resin, which may be contributed to the specific surface area and the partial polarity on the network. Estimations of the isosteric enthalpy, free energy, and entropy for the adsorption process were reported.

PROPERTIES AND THERMODYNAMICS OF ADSORPTION OF BENZOIC ACID ONTO XAD-4 AND A WATER-COMPATIBLE HYPERCROSSLINKED ADSORBENT

The adsorption behavior of benzoic acid onto a water-compatible hypercrosslinked polymeric adsorbent NJ-8 wascompared with that onto macroporous Amberlite XAN-4. This paper focuses on the static equilibrium adsorption behaviors,the adsorption thermodynamics and the column dynamic adsorption profiles. Five isotherm models are used to fit the results.This shows that the Freundlich equation can give a perfect fit. The specific surface area of NJ-8 is about as high as that ofAmberlite XAD-4, but the adsorbing capacity for benzoic acid on NJ-8 is about 14.9%-64.8% higher than that on AmberliteXAD-4, which is attributed to its microporous mechanism and partial polarity. The negative values of the adsorptionenthalpy are indicative of an exothermic process. Both enthalpy and free energy changes of adsorption manifest a physicalsorption process. The negative values of the adsorption entropy indicate that adsorption is well consistent with the restrictedmobilities and the configurations of the adsorbed molecules on the surface of the studied adsorbents with superficialheterogeneity. Both adsorbents were used in mini-column experiments to demonstrate the higher breakthrough adsorbing capacity of the hypercrosslinked polymeric adsorbent NJ-8 to benzoic acid, as compared with that of Amberlite XAD-4.