The comparison of Cu(II) adsorption capability of baker’s yeast, nano-titania and their composite adsorbent

The anatase nano-TiO2 powder, with crystal size between 40 and 80 nm, was prepared by the liquid phase hydrolysis of TiCl4. At the same time, the nano-TiO2 was utilized with the baker’s yeast biomass as a composite adsorbent to adsorb the Cu ions in the artificial aqueous solution. The investigation showed that the composite adsorbent had a fine adsorption efficiency. The TiO2 in the composite ad- sorbent could cooperate well with baker’s yeast to improve the adsorbing capability of Cu2 under the following experimental conditions as well: a quantity of composite adsorbent of 5 g·L?1, pH≥4.0, an adsorption time of 40 min and an initial concentration of Cu ions of 10 mg·L?1. In addition, the results of measurements, obtained with a scanning electron microscope, an infrared spectrophotometer and a Zeta potential analyzer, revealed that the baker’s yeast and nano-TiO2 produced the composite ad- sorbent through coordination and hydrogen bonds in particular, etc. The stability of the composite adsorbent and the amount of titania loaded were largely dependent on the concentration of hydrogen ion in the solution.     

Characterization and adsorption behavior of a novel triolein-embedded activated carbon composite adsorbent

A novel triolein-embedded activated carbon composite adsorbent was developed. Experiments were carried out in areas such as the preparation method, the characterization of physicochemicai properties, and the adsorption behavior of the composite adsorbent in removing dieldrin from aqueous solution. Results suggested that the novel composite adsorbent was composed of the supporting activated carbon and the surrounding triolein-embedded cellulose acetate membrane. The adsorbent was stable in water, for no triolein leakage was detected after soaking the adsorbent for five weeks. The adsorbent had good adsorption capability to dieldrin, which was indicated by a residual dieldrin concentration of 0.204μg·L^-1. The removal efficiency of the composite adsorbent was higher than the traditional activated carbon adsorbent.     

Synthesis of a copper(Ⅱ) oxide-montmorillonite composite for lead removal

The synthesis of a copper(Ⅱ) oxide-montmorillonite composite and its application in the removal of lead(Ⅱ) ions in solution were investigated. The Acros Organics (ACOR) montmorillonite was activated using potassium hydroxide solution. The activated ACOR montmorillonite was titrated with copper(Ⅱ) nitrate solution to produce the copper(Ⅱ) oxide-montmorillonite composite. Adsorption experiments were conducted using batch-mode techniques under reducing conditions at ambient temperature. The reaction mechanism indicated a higher proton coefficient, greater intraparticle diffusion, and higher mass transfer rates compared with those achieved with bare montmorillonite. The intraparticle diffusion constant derived from the slope was 2.93-3 (mg·g-1·min-0.5), and the intercept C was 9.86, ≠ 0. In the presence of a CuO coating, the adsorption efficiency was 85.55% at pH 4 and 89.62% at pH 7. Therefore, the copper(Ⅱ) oxide-montmorillonite composite, as a novel adsorbent with a very high adsorption capacity, exhibited substantially enhanced adsorption of Pb2+ ions compared with bare montmorillonite.     

Adsorption recovery of Ag(I) and Au(III) from an electronics industry wastewater on a clay mineral composite

The aim of this work is to investigate the ability of an adsorbent of a clay mineral composite to remove and recover gold and silver ions from wastewater. The composite was prepared by mixing phosphogypsum (PG), obtained from an industrial waste, and a natural clay mineral. The materials were characterized before and after use in adsorption by several techniques. Batch adsorption experiments were carried out, and the effects of the contact time and the pH and temperature of solution on the removal processes were investigated. The optimum pH for the adsorption was found to be 4. The adsorption of these metal ions reached equilibrium after 2 h of contact. The pseudo-first- and the pseudo-second-order kinetic models, as well as the Freundlich and the Langmuir isotherm equations, were considered to describe the adsorption results. The maximum adsorbed amount of 85 mg·g-1 Ag(I) and 108.3 mg·g-1 Au(Ⅲ) was found. The recovery of the adsorbed gold and silver ions from the adsorbent was also analyzed. Strong acids appeared to be the best desorption agents to recover gold and silver ions. The use of aqua regia gave regeneration rates close to 95.3% and 94.3% for Ag(I) and Au(Ⅲ), respectively. Finally, the removal of gold and silver ions from an industrial wastewater was tested in batch experiments, and percentage recoveries of 76.5% and 79.9% for Ag(I) and Au(Ⅲ), respectively, were obtained. To carry out the industrial application of the proposed methodology, an economic viability study is required.     

Equilibrium,Kinetics and Thermodynamics of the Adsorption of Methylene Blue onto a Metal-Organic Frameworks Material,Copper Coordination Polymer with Dithiooxamide

The equilibrium, kinetics and thermodynamics of the adsorption of methylene blue （MB） from aqueous solution onto copper coordination polymer with dithiooxamide （H2dtoaCu） , one of the metal-organic frameworks （MOFs）, were investigated in a batch adsorption system as a function of initial pH, adsorbent concentration, contact time, initial dye concentration, and temperature. The Langmnir, Freundlich, and Dubinin- Radushkevich （D-R） isotherm models were used for modeling the adsorption equilibrium. It was found that Langmuir model yielded a much better fit than the Freundlich model under different temperatures. The maximum monolayer adsorption capacities of MB were 192.98, 229.86, and 297.38 mg/g at 298, 308, and 318 K, respectively. The calculated mean adsorption energy （8.26- 11.04 kJ/mol） using D-R model indicated that the adsorption process might take place by chemical adsorption mechanism. Otherwise, the kinetic studies revealed that the adsorption process could be well explained by pseudo-second-order rate kinetics and intraparticle diffusion was not the rate-limiting step. Thermodynamic studies indicated that this system was feasible, spontaneous, and endothermic process. Based on these studies, H2dtoaCu can be considered as a potential adsorbent for the removal of MB from aqueous solution.     

Hexavalent Chromium Adsorption from Aqueous Solution by Agricultural Waste Materials

Abilities of agricultural waste materials (walnut shell-WS, rice husk-RH, and peanut hull-PH) were tested as adsorbents for the adsorption of Cr(Ⅵ) from aqueous solution. Batch adsorption experiments were carried out to study the adsorption kinetics mechanism of Cr(Ⅵ) effect of adsorbent dosage, pH, contact time, and temperature. The best results are obtained at 15g/L adsorbent concentration, 60min contact time, 298K temperature, and 50mg/L adsorbate initial concentration at pH 2. The adsorption isotherms, using initial concentrations of Cr(Ⅵ) between 10 and 500mg/L for the Cr(Ⅵ) removal, show the maximum metal uptake capacities of adsorbent were 10.48, 6.71, and 8.54mg/g for WS, RH, and PH, respectively. And the adsorption data fitted well to the Langmuir adsorption isotherm for WS, RH, and PH with correlation coefficients of 0.9862, 0.9723, and 0.9714, respectively. Moreover, the FTIR analysis of WS, RH, and PH before and after adsorption of Cr(Ⅵ) suggested that Cr ions were combined to some functional groups of compounds contained in these materials.     

Copper Adsorption on Olivine

Copper adsorption on olivine supplied by the A/S Olivine Production Plant at Aheim in western Norway was studied. The factors were evaluated which affect the uptake of copper. It is shown that the equilibrium pH of aqueous solution has the greatest influence on copper adsorption thanks to the competitive adsorption between proton and copper ions, and the adsorption of copper to olivine increases rapidly with pH increasing from 4 to 6. Moreover, initial copper concentration and olivine dose possess significant effect on copper adsorption, for the adsorption rate of copper increases with olivine dose increasing or initial copper concentration decreasing at the same pH. In addition, the ionic strength effect on the adsorption was also investigated, but it owns little effect on the adsorption process of copper due to the formation of inner sphere adsorption of copper on olivine. The experimental data show that olivine has a high acid buffer capacity and is an effective adsorbent for copper.     

Efficient adsorption of As(V) on poly(acrylo-amidino ethylene amine) nanofiber membranes

Poly(acrylo-amidino ethylene amine) (PAEA) nanofiber membranes have been synthesized by combining the electrospinning technique and subsequent chemical modification. The membranes were used to remove As(V) from aqueous solution. The adsorption kinetics, equilibrium isotherms, and pH effect were investigated in batch experiments. The Langmuir isotherm and pseudo second-order kinetic models agree well with the experimental data. The PAEA nanofibers are effective for As(V) adsorption at pH 3. Experimental results showed that the maximum adsorption capacity of the PAEA nanofibers with As(V) is 76.92 mg g-1 , which is much higher than that of the PAEA microfibers (27.62 mg g-1 ). The adsorption rate of PAEA nanofibers is faster than that of PAEA microfibers due to its higher specific surface area. The PAEA nanofibers can be used as an effective adsorbent for the removal of As(V) in aqueous solution due to high adsorption capacity and short adsorption time to achieve equilibrium.     

Preparation of composite adsorbent with high performance of heat and mass transfer

To develop a new composite adsorbent with high performance,fir sawdust and CaCl2are selected as raw materials.The mass transfer is enhanced by carbonizing and activating the sawdust and heat transfer is enhanced by adding expanded graphite into the adsorbent.The effect of the preparation temperature and the expanded graphite content on the adsorption performance is investigated.The results show that the new adsorbent exhibits a high adsorption performance due to its high porosity,uniform distribution and high content of CaCl2and high thermal conductivity.Also,the experimental results indicate that the rate of ammonia adsorption on the adsorbent depends on the expanded graphite content and the carbonization and activation temperature.The adsorbent prepared at 500°C and with the expanded graphite content of 30%has the best performance in terms of the adsorption refrigeration,which adsorbs ammonia as high as 0.37 g g 1at 10 min.     

Synthesis,characterization, and property test of crystalline polyferric sulfate adsorbent used in treatment of contaminated water with a high As(Ⅲ) content

A crystalline polyferric sulfate(PFS) adsorbent was synthesized by oxidizing and precipitating ferrous ions in air atmospheric conditions. The morphology, structure, specific surface area(SSA), and adsorptive efficacy of the adsorbent to As(Ⅲ) were characterized by scanning electron microscope(SEM) and transmission electron microscopy(TEM) images, X-ray diffraction(XRD) patterns, Fourier-transform infrared(FTIR) spectra, BET SSA analyses, and adsorption experiments. The adsorbent showed a near-spherical aggregate structure and had good crystallinity. A significant amount of α-goethite co-precipitated with PFS in the case of the initial ferrous concentration of 1 mol/L and increased SSA of the adsorbent. The stability region of ferric compounds in the process was drawn and applied to analyze the iron behavior during the synthesis. The adsorption of As(Ⅲ) in high As(Ⅲ)-containing solutions fitted the Langmuir isotherm model adequately. The absorbent with co-precipitation of α-goethite showed good adsorbability for As(Ⅲ) and good filtering performance in the high As(Ⅲ)-containing solution of 10–100 mg/L under acidic, neutral, and alkaline conditions(pH 2.09–9.01). After the adsorption process, the stability of the residues bearing As(Ⅲ) was evaluated by toxic characteristic leaching procedure(TCLP) tests. The results indicated that the residues were extremely stable, and the concentrations of arsenic in the leaching solutions were less than 0.01 mg/L.     

Study on copper adsorption on olivine

The copper adsorption on olivine supplied by A/S Olivine production plant at Aheim in western Norway has been studied. The factors which affect the uptake of copper have been evaluated. The results reveal that the equilibrium PH in aqueous solution has the greatest influence on the copper adsorption thanks to the competitive adsorption between proton and copper ions, and the adsorption of copper to olivine increases rapidly with the pH increasing from 4 to 6. The initial copper concentration and olivine dose also possess significant effect on copper adsorption. The adsorption efficieny of copper increases with the increase of olivine dose or the decrease of initial copper concentration at the same pH. The ionic strength effect on the adsorption has also been investigated, but it owns little effect on the adsorption process of copper due to the formation of inner sphere surface complexation of copper on olivine. The experimental data show that olivine has a high acid buffer capacity and is an effective adsorbent for copper.     

Lead removal from aqueous solution by employing natural brucite

The effect and mechanism of the removal of Pb2+ from an aqueous solution by using brucite as the adsorbent were studied.It was revealed that the increase in pH of brucite suspension, as a result of the release of magnesium hydroxide into the suspension,leads to a sharp rise of the adsorption amount of Pb2+ on brucite. The synergism of buffering and adsorption capacities of brucite is responsible for the removal of Pb2+ from the aqueous solution. The coexistence of Cu2+ with Pb2+ causes a decrease of their adsorption on brucite due to a competition for surface sites and brucite exhibits a higher adsorption capacity for Pb2+ than for Cu2+. The percentage adsorption of Pb2+ on brucite could reach 96.38%, 97.20% and 94.09% respectively with the initial pH of the suspension pH_i = 1.76 (initial Pb2+ concentration [Pb2+]_i = 20 μmol/L), 1.82 ([Pb2+]_i = 100 μmol/L) and 1.84 ([Pb2+]_i = 500 μmol/L). It was concluded that brucite is a very efficient mineral adsorbent for Pb2+ removal from polluted acidic water.     

Adsorption of Fluoride Ion by Inorganic Cerium Based Adsorbent

Excess of fluoride in drinking water is harmful to human health, the concentration of F^- ions must be maintained in the range of 0.5 to 1.5 mg/L. An inorganic cerium based adsorbent (CTA) is developed on the basis of research of adsorption of fluoride on cerium oxide hydrate. Some adsorption of fluoride by CTA adsorbent experiments were carried out, and results showed that CTA adsorbent has a quick adsorption speed and a large adsorption capacity. Adsorption follows Freundlich isotherm, and low pH value helps fluoride removal. Some physical-chemical characteristics of CTA adsorbent were experimented, fluoride removal mechanism was explored, and results showed that hydroxyl group of CTA adsorbent played an important role in the fluoride removal.     

Adsorption characteristics of Cd(II) and Ni(II) from aqueous solution using succinylated hay

An environmentally friendly organic biosorbent was fabricated using hay by succinylation. Metallic cation adsorption tests were performed using synthetic nickel(Ⅱ) and cadmium(Ⅱ) solutions to simulate heavy-metal recovery from aqueous solution. The adsorption efficiency was greater than 98% for both cadmium and nickel ions when the biosorbent concentration was 5.0 g/L and the initial metal concentrations were 50 mg/L. The surface of the biosorbent was characterized using Fourier transform infrared spectroscopy to investigate the changes in the surface functional groups. The functional groups changed according to the surface treatment, resulting in an effective biosorbent. The kinetics of the metals adsorption revealed that the reactions are pseudo-second order, and the adsorption isotherm well followed the Langmuir model. The maximum adsorption capacities predicted by the Langmuir model were 75.19 mg/g and 57.77 mg/g for cadmium and nickel, respectively. The fabricated biosorbent was regenerated using NaCl multiple times, with 2.1% for Cd and 4.0% for Ni in adsorption capacity after three regeneration cycles. The proposed biosorbent can be a good alternative to resin or other chemical adsorbents for heavy-metal recovery in metallurgical processing or municipal water treatment.     

A Composite of Crosslinked and Quaternized Poly (4-vinylpyridine) and Polypyrrole as a Potential Candidate for the Detection of Low Humidity

1 Results Despite rapid progress in the development of resistive-type humidity sensors, the detection of low humidity is still a problem[1, 2]. In this study, poly(4-vinylpyridine) was crosslinked and quaternized with 1,4-bromobutane to form a polyelectrolyte humidity sensitive film on interdigitated gold electrodes, which was further coated with a layer of polypyrrole by a facile method of vapor phase polymerization process. The composite so prepared was characterized by UV-vis spectroscopy and scanning electron microscopy. It was found that the impedance of the composite changed linearly with humidity in the range of 0～60%RH with good sensitivity. In addition, it exhibited a fast response (t90%: ≈33 s and ≈110 s for adsorption and desorption, respectively) and a relative small hysteresis (≈5%RH). The effect of concentration and ratio of oxidizing agent and dopingagent, temperature of vapor phase polymerization of pyrrole on the humidity sensitive properties of the composite have been investigated. The sensitive mechanism of the composite was also explored. The composite of conducting PPy and polyelectrolyte has great potential as a candidate sensitive material forlow humidity detection.     

Adsorption and catalytic combustion of ARB on CuO-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

CuO-Fe2O3 composite material with strong magnetism and a large surface area is prepared by the co-precipitate method. Its adsorption properties towards Acid Red B (ARB) and the regeneration by catalytic combastion of organic compounds have been studied. The results show that the prepared CuO-Fe2O3 composite is an excellent adsorbent for ARB adsorption at acid condition. The presence of Cl^- has no effect on ARB adsorption. But the SO4^2- can inhibit ARB adsorption. After being recovered by the magnetic separation method, the adsorbent can be regenerated by catalytic oxidation of absorbate at 300℃ in air atmosphere. The combustion reactions of ARB in the presence or absence of CuO-Fe2O3 are studied by in situ diffuse refieclion FTIR. The results indicate that, in the presence of CuO-Fe2O3, the degradation temperature is significantly lowered by the catalysis of CuO-Fe2O3, and ARB can be oxidized completely without volatile organic compound by-product; in comparison, in the absence of CuO-Fe2O3, the temperature needed for oxidation of ARB is higher and the reaction is incomplete with some N-containing harmful compounds produced. The reusability of CuO-Fe2O3 is also studied in successive seven adsorption-regeneration cycles.     

Adsorption and Fenton Synergistic Process Using Magnetic Co-Fe-Biochar Microsphere for the Removal of Dyes from Aqueous Solution

To attain a low-cost and high-efficient adsorbent and Fenton catalyst, sludge biochar/nano-cobalt(Co-Biochar) and sludge biochar/nano-cobalt/iron(Co-Fe-Biochar) composites were prepared to use as raw materials, and iron and nano-cobalt as modifiers with a hydrothermal method at 180°C for 3 h. The adsorption effect of different composite materials on low concentration Congo red dyes and synergistic effect of adsorption and high oxidation on high concentration Congo red dyes were studied. The results show that Co-Fe-Biochar has not only adsorption to Congo red dyes but also strong advanced oxidation. The removal rate of Co-Fe-Biochar to high concentration Congo red dyes is as high as 82%. Co-Fe-Biochar were characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), nitrogen absorption and desorption(BET), hysteresis loop(VSM), and Fourier transform infrared spectrum(FTIR). It is known that the prepared composite material is a microsphere structure in which nano cobalt is the core and the iron carbon layer is the outer shell. Moreover, the addition of nano cobalt makes the composite have a porous morphology, with the specific surface area of the composite increased from 54.024 m~2/g to 117.753 m~2/g.     

Synthesis,characterization, and property test of crystalline polyferric sulfate adsorbent used in treatment of contaminated water with a high As(III) content

A crystalline polyferric sulfate (PFS) adsorbent was synthesized by oxidizing and precipitating ferrous ions in air atmospheric conditions. The morphology, structure, specific surface area (SSA), and adsorptive efficacy of the adsorbent to As(Ⅲ) were characterized by scanning electron microscope (SEM) and transmission electron microscopy (TEM) images, X-ray diffraction (XRD) patterns, Fourier-transform infrared (FTIR) spectra, BET SSA analyses, and adsorption experiments. The adsorbent showed a near-spherical aggregate structure and had good crystallinity. A significant amount of α-goethite co-precipitated with PFS in the case of the initial ferrous concentration of 1 mol/L and increased SSA of the adsorbent. The stability region of ferric compounds in the process was drawn and applied to analyze the iron behavior during the synthesis. The adsorption of As(Ⅲ) in high As(Ⅲ)-containing solutions fitted the Langmuir isotherm model adequately. The absorbent with co-precipitation of α-goethite showed good adsorbability for As(Ⅲ) and good filtering performance in the high As(Ⅲ)-containing solution of 10-100 mg/L under acidic, neutral, and alkaline conditions (pH 2.09-9.01). After the adsorption process, the stability of the residues bearing As(Ⅲ) was evaluated by toxic characteristic leaching procedure (TCLP) tests. The results indicated that the residues were extremely stable, and the concentrations of arsenic in the leaching solutions were less than 0.01 mg/L.     

Direct electrochemistry and electrocatalysis of horseradish peroxidase in MnO2 nanosheet film

A novel material MnO2 nanosheet has been used as the support matrix for the immobilization of horseradish peroxidase （HRP）. HRP entrapped in MnO2 nanosheet film exhibits facile direct electron transfer with the electron transfer rate constant of 6.86 s^-1. The HRP/MnO2 nanosheet film gives a reversible redox couple with the apparent formal peak potential （E^0＇） of -0.315 V （vs. Ag/AgCl） in pH 6.5 phosphate buffer solution （PBS）. The formal potential E^0＇ of HRP shifts linearly with pH with a slope of -53.75 mV.pH^-1, denoting that an electron transfer accompanies single-proton transportation. The immobilized HRP shows an electrocatslytic activity to the reduction of H2O2. The response time of the biosensor for H2O2 is less than 3 s, and the detection limit is 0.21 μmol · L^-1 based on signal/noise = 3.     

Enhanced Removal of Tetracycline from Aqueous Solution by Graphene Oxide Hydrogel Doped with TiO_2 Nanotubes

The detection on tetracycline( TC) in drinking water poses an environmental issue since TC has been widely used to prevent animal disease and promote their growth. In addition,TC was difficult to remove or biodegrade,which posed a challenge to the conventional techniques. In this work,the batch experiments on TC adsorption in aqueous solution of hydrogel( HG) consisting of graphene oxide( GO) and TiO_2 nanotubes( TN) were successfully conducted. HG composite( HG-TN-GO) was prepared with TN and GO with self-assembly method during the oxidation-reduction reaction,and criogel( CG) with TN and GO was characterized by pH at point of zero charge( pH_(pzc)), transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy( XPS). The adsorption capacity of HG-TN-GO on TC was evaluated by analyzing its isotherms. The maximum adsorption capacity reached 751. 3 mg/g. Besides,the adsorption isotherms were well fitted by the Langmuir model, with the theoretical maximum( q_m) of 797. 0 mg/g. The adsorption process was systematically studied by varying pH during the whole adsorption process. The adsorption occurred probably via π-π interaction and cation-π bonding between TC and the HG-TN-GO surface. The composite could be regenerated in 50% ethanol aqueous solution,without significant capacity loss. After 6 recycles,the decrease of adsorption capacity was less than 10%.