Shengrui Tong

One-step synthesis of magnetic composites of cellulose@iron oxide nanoparticles for arsenic removal

Composite materials, containing magnetic nanoparticles and cellulose, were synthesized by one-step co-precipitation using NaOH–thiourea–urea aqueous solution for cellulose dissolution. The NaOH in cellulose solution acted as the precipitant of iron oxide nanoparticles, and low-cost cellulose was used as the template to promote the growing of nanoparticles in the cellulose matrix. The method provided a facile, “green” pathway for the fabrication of magnetic nanomaterials. The synthesized cellulose@iron oxide nanoparticles were characterized by FTIR, XRD, SEM, TEM, XPS, TG and VSM. The FTIR, XRD and XPS results demonstrated the formation of Fe2O3 nanoparticles in the composite materials after the co-precipitation. SEM and TEM characterization showed that the Fe2O3 nanoparticles were dispersed in the cellulose matrix due to the synergistic effect. Magnetometric measurements revealed that the resultant composites of cellulose@Fe2O3 nanoparticles exhibited a sensitive magnetic-induced behavior and could be easily separated from aqueous solution through the external magnetic field. The composite materials were applied to remove arsenic from aqueous solution. The results showed that the magnetic nanoparticle composites displayed excellent adsorption efficiency of arsenic compared with other magnetic materials reported, and the Langmuir adsorption capacities of the composites for the removal of arsenite and arsenate were 23.16 and 32.11 mg g−1, respectively.

Adsorption of heavy metal ions from aqueous solution by carboxylated cellulose nanocrystals

A novel nanoadsorbent for the removal of heavy metal ions is reported. Cotton was first hydrolyzed to obtain cellulose nanocrystals (CNCs). CNCs were then chemically modified with succinic anhydride to obtain SCNCs. The sodic nanoadsorbent (NaSCNCs) was further prepared by treatment of SCNCs with saturated NaHCO3 aqueous solution. Batch experiments were carried out with SCNCs and NaSCNCs for the removal of Pb2+ and Cd2+. The effects of contact time, pH, initial adsorption concentration, coexisting ions and the regeneration performance were investigated. Kinetic studies showed that the adsorption equilibrium time of Pb2+ and Cd2+ was reached within 150 min on SCNCs and 5 min on NaSCNCs. The adsorption capacities of Pb2+ and Cd2+ on SCNCs and NaSCNCs increased with increasing pH. The adsorption isotherm was well fitted by the Langmuir model. The maximum adsorption capacities of SCNCs and NaSCNCs for Pb2+ and Cd2+ were 367.6 mg/g, 259.7 mg/g and 465.1 mg/g, 344.8 mg/g, respectively. SCNCs and NaSCNCs showed high selectivity and interference resistance from coexisting ions for the adsorption of Pb2+. NaSCNCs could be efficiently regenerated with a mild saturated NaCl solution with no loss of capacity after two recycles. The adsorption mechanisms of SCNCs and NaSCNCs were discussed.

Removal of fluoride from drinking water by cellulose@hydroxyapatite nanocomposites

Cellulose@hydroxyapatite (HA) nanocomposites were prepared in NaOH/thiourea/urea/H(2)O solution via situ hybridization. The composite materials combine the advantage of cellulose and HA with the high specific surface area and the strong affinity toward fluoride. The composite materials were characterized by FTIR, SEM, XRD, TG and XPS, and the adsorption of fluoride was investigated. Adsorption kinetics indicated the adsorption equilibrium of fluoride was within 360 min and the adsorption process was well described by the pseudo-second-order kinetic model. The Langmuir and Freundlich isotherm models could fit the experimental data well. At the initial fluoride concentration of 10mg/L, the residual concentration using above 3g/L adsorbent dose could meet the drinking water standard of WHO norms. Furthermore, the coexisting anions had no significant effect on fluoride adsorption.

Synthesis and characterization of multi-amino-functionalized cellulose for arsenic adsorption

A multi-amino adsorbent for arsenic adsorption was reported in this paper. Glycidyl methacrylate (GMA) was first grafted onto the surface of cotton cellulose using ceric ammonium nitrate (CAN) as the initiator, and then the introduced epoxy groups reacted with tetraethylenepentamine (TEPA) to obtain a multi-amino adsorbent. The adsorbent was characterized by FTIR, elemental analysis, (13)C NMR and SEM. Then, the adsorption of arsenic for this adsorbent was investigated. The results showed that the GMA and TEPA were successfully grafted onto the surface of cellulose, and the modification improved the arsenic adsorption performances. Kinetic study suggested that the chemisorptions were the rate-limiting step. Among the three adsorption isotherm models used, Langmuir model fitted the experimental data best. The adsorption capacities of arsenic were less affected by coexisting ions. The adsorbent could be effectively regenerated for four cycles with 0.1 mol/L NaOH solution.

Heterogeneous reaction of NO2 on Al2O3: the effect of temperature on the nitrite and nitrate formation.

Although recent evidence suggests that the heterogeneous reaction of NO2 on the surface of mineral aerosol plays an important role in the atmospheric chemistry, a fundamental understanding of how temperature influences the rate and extent of nitrate formation processes remains unclear. This work presents the first laboratory study of the effect of temperature on heterogeneous reaction of NO2 on the surface of γ-Al2O3 in the temperature range of 250-318 K at ambient pressure. From the analysis of IR spectra, nitrite was found to be an intermediate product at temperatures between 250 and 318 K. It is proved by our experiments that nitrite would convert to the bidentate nitrate as the reaction proceeded. In addition, it is interesting to find that the rate of conversion increased with decreasing temperature. Along with nitrite decrease, the initial rate of nitrate formation increased while the rate of nitrate formation in the steady region decreased with decreasing temperature. The uptake coefficients at seasonal temperatures were determined for the first time and were found to be sensitive to temperature. Finally, atmospheric implications of the role of temperature on the heterogeneous reaction of NO2 with mineral aerosol are discussed.

Fe3+ and amino functioned mesoporous silica: preparation, structural analysis and arsenic adsorption.

Two novel adsorbents to remove excess arsenate and arsenite in the drinking water were prepared for the first time by grafting monoamine and diamine, respectively, and then coordinating Fe(3+) on silica gel that was obtained using sol-gel method with two-step acid-base catalysis. It was found that both adsorbents had mesoporous structure, large specific surface, and high amino and iron content according to N(2) adsorption isotherms, FTIR, XPS, and NMR analysis. The removal ability and adsorption rate of the adsorbents were very high for both As(V) and As(III). Langmuir and Freundlich models were used to fit the adsorption isotherm and investigate the adsorption mechanism. The effects of chloride and sulfate anion on the removal of arsenate and arsenite for the two adsorbents were also studied.

One-pot synthesis of porous magnetic cellulose beads for the removal of metal ions

Porous magnetic cellulose beads have been successfully prepared via a facile one-pot wet extrusion by in situ depositing CoFe2O4 nanoparticles on cellulose beads. Cellulose beads serve as a template to prevent CoFe2O4 particles from aggregating. The deposited CoFe2O4 nanoparticles are tightly entrapped within cellulose beads because of the strong attractive interactions between the cellulose beads and CoFe2O4 particles. The functionalized cellulose beads can be easily separated from aqueous solution by the external magnetic field. The encapsulated CoFe2O4 nanoparticles act as the magnetic substrate and the active sites to adsorb metal ions. An attractive feature of this preparation method is that it is versatile to prepare a variety of cellulose-based functional nanocomposites in the form of macroscopic beads by incorporating functional particles into the pores of cellulose beads.

Synergistic Effects between SO2 and HCOOH on α-Fe2O3

Heterogeneous reactions on mineral aerosols remain an important subject in atmospheric chemistry because of their role in altering the properties of particles and the budget of trace gases. Yet, the role of coadsorption of trace gases onto mineral aerosols and potential synergistic effects are largely uncertain, especially synergistic effects between inorganic and organic gas-phase pollutants. In this study, synergistic effects between HCOOH and SO2 were investigated for the first time using in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS). It was found that the heterogeneous reaction of HCOOH is hindered significantly by coexisting SO2. The total amount of formate decreased, whereas the total amount of sulfate was not affected during coadsorption on the surface of α-Fe2O3. Futhermore, part of the formate on the surface was catalytically decomposed to CO2 by α-Fe2O3 with the help of SO2. These results suggest a possible mechanism for the observed correlations between sulfate and carboxylate in the atmosphere.

Template-free synthesis of 3D hierarchical amorphous aluminum oxide microspheres with broccoli-like structure and their application in fluoride removal

3D hierarchical amorphous aluminum oxide microspheres with broccoli-like structures were synthesized successfully via a facile method without using any template. A multistep crystal adsorption-splitting growth mechanism is proposed to understand the formation of this material. It displayed an excellent adsorption performance for fluoride, and the adsorption capacity can reach 126.9 mg g−1.

Influence of Temperature on the Heterogeneous Reaction of Formic Acid on α-Al2O3

Despite increased awareness of the role played by heterogeneous reactions of formic acid on mineral aerosol, the experimental determination of how these atmospheric reaction rates vary with temperature remain a crucially important part of atmosphere science. Here we report the first measurement of heterogeneous uptake of formic acid on α-Al(2)O(3) as a function of temperature (T = 240-298 K) at ambient pressure using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). From the analysis of the spectral features, crystalline HCOOH was identified at low temperature besides common product (formate ions) on the surface. It was also interesting to find that crystalline HCOOH can continue to react with α-Al(2)O(3). The reaction mechanisms at both room and low temperature were discussed. Furthermore, the reactive uptake coefficients were acquired and found to increase with decreasing temperature. Finally, the atmospheric lifetime of formic acid because of heterogeneous loss on mineral aerosol was estimated at temperatures related to the upper troposphere.