Reconstruction of the ZnAl Mixed Oxides Into the Layered Double Hydroxide Catalysts Active in the Aldol Condensation of Furfural: The Role of ZnO Particles

A memory effect is the ability to restore the original, lamellar layered double hydroxide structure. Herein, we have described 1) the changes in the structural and basic properties of ZnAl mixed oxides during their transformation into ZnAl-reconstructed LDHs (RE-LDHs); 2) the extraordinary properties of ZnAl RE-LDHs compared to the original ZnAl LDHs; and 3) the changes of basic properties during the interaction of ZnAl RE-LDHs with atmospheric CO2. Aldol condensation was selected as probe reaction to prove the catalytic potential of ZnAl RE-LDHs. We have described a target method for preparing ZnAl RE-LDHs with a large number of basic sites. ZnAl RE-LDHs possess significantly higher furfural conversion in the aldol condensation of furfural than MOs. The structural, textural, and basic properties of the studied materials were described by temperature-programmed analysis, X-ray diffraction, N2 adsorption, temperature-programmed desorption of CO2, and in-situ diffuse reflectance spectroscopy.

Surface modification of nano-TiO2 with lanthanide-acetylacetonate complexes

The surface modification of nano-TiO2 was carried out with lanthanide-acetylacetonate complexes by adsorption method. The effects of lanthanide complexes content, lanthanide element type, adsorption temperature, solvent dosage, adsorption time and other conditions on the photodegradation activity of methyl orange by the modified catalyst were studied, and suitable modification conditions were obtained. The results show that the photocatalytic activity of the modified nano-TiO2 is much higher than that of the unmodified pure TiO2, and the lanthanide-acetylacetonate complexes is an excellent surface modifier.

CO2 Adsorption and Desorption by Waste Ion-Exchange Resin–Based Activated Carbon on Fixed Bed

The waste ion-exchange resin–based activated carbon (WIRAC) was utilized for CO2 adsorption. The effect of adsorption temperature, gas flow, CO2 concentration, and adsorbent filling content on CO2 adsorption properties of WIRAC and the effect of desorption temperature and sweep gas flow on CO2 desorption performances of WIRAC were researched. In the adsorption process, with the increase of adsorption temperature, the CO2 adsorption capacity and adsorption rate decrease; as the gas flow increases, the CO2 adsorption capacity decreases, but the adsorption rate increases; with the increase of CO2 concentration and adsorbent filling content, the CO2 adsorption capacity and adsorption rate both increase. In the desorption process, the higher the desorption temperature and the smaller the sweep gas flow, the higher the CO2 purity of product gas and the longer the desorption time. In order to make sure the adsorbent be used efficiently and the higher CO2 concentration of product gas, the adsorption and desorption conditions selected should be a suitable choice.

Synthesis of Calcium Silicate Hydrate from Coal Gangue for Cr(VI) and Cu(II) Removal from Aqueous Solution

Both the accumulation of coal gangue and potentially toxic elements in aqueous solution have caused biological damage to the surrounding ecosystem of the Huainan coal mining field. In this study, coal gangue was used to synthesize calcium silicate hydrate (C-S-H) to remove Cr(VI) and Cu(II)from aqueous solutions and aqueous solution. The optimum parameters for C-S-H synthesis were 700 °C for 1 h and a Ca/Si molar ratio of 1.0. Quantitative sorption analysis was done at variable temperature, C-S-H dosages, solution pH, initial concentrations of metals, and reaction time. The solution pH was precisely controlled by a pH meter. The adsorption temperature was controlled by a thermostatic gas bath oscillator. The error of solution temperature was controlled at ± 0.3, compared with the adsorption temperature. For Cr(VI) and Cu(II), the optimum initial concentration, temperature, and reaction time were 200 mg/L, 40 °C and 90 min, pH 2 and 0.1 g C-S-H for Cr(VI), pH 6 and 0.07 g C-S-H for Cu(II), respectively. The maximum adsorption capacities of Cr(VI) and Cu(II) were 68.03 and 70.42 mg·g−1, respectively. Furthermore, the concentrations of Cu(II) and Cr(VI) in aqueous solution could meet the surface water quality standards in China. The adsorption mechanism of Cu(II) and Cr(VI) onto C-S-H were reduction, electrostatic interaction, chelation interaction, and surface complexation. It was found that C-S-H is an environmentally friendly adsorbent for effective removal of metals from aqueous solution through different mechanisms.

Adsorption Behavior of Lead Ions from Wastewater on Pristine and Aminopropyl-Modified Blast Furnace Slag

The potential possibility of blast furnace slag as a low-cost adsorbent to remove lead ions from wastewater was investigated in detail in the present work. Both single factor experiment and orthogonal experiment were performed to reveal the effect of pH, adsorption temperature, contact time and initial concentration of lead ions on the adsorption performance of pristine slag. In order to make clear the correlation between the lead ion adsorption performance and the structure of slag, solid state nuclear magnetic resonance (NMR) was conducted to reveal the network structure and X-ray fluorescence (XRF) was used to calculate the nonbridging oxygen in the network-forming tetrahedra. For the purpose of improving the adsorption performance, γ-aminopropyltriethoxysilane (APTES) was adopted to modify the slag via post-grafting method. The results show that the slag is predominately composed of SiO2, Al2O3, CaO and MgO, exhibiting an amorphous network structure based on SiO4 and AlO4 tetrahedra. The conditions for adsorption can be optimized as follows: a pH of 7, an adsorption temperature of 60 °C, a contact time of 120 min and an initial lead ion concentration of 40 mg·L−1. Under the optimal conditions, a removal rate of 99.98% and an adsorption capacity of 49.99 mg·g−1 are obtained for the pristine slag. The adsorption complies with the Langmuir model thermodynamically and conforms to the pseudo-second order model kinetically. It is noted that aminopropyl-modification has considerably enhanced the removal rate of lead ions from 20.71 to 64.32% and the adsorption capacity from 29.01 to 96.48 mg·g−1 since amino groups (-NH2) are more inclined to form a complex with lead ions than hydroxyl groups due to the higher nucleophilicity of amino groups than that of hydroxyl groups. However, it is necessary to develop more low-cost modification agents in the future work.

Performance of Calcium Chloride- Ammonia Adsorption Refrigeration System

An experimental study on the performance of calcium chloride-ammonia adsorption system is described. A single bed water cooled condenser adsorption refrigerator prototype, which utilises calcium chloride-ammonia pair has been developed and tested in the laboratory. Experiments have been conducted for desorption temperatures of 100 °C with desorption time varying from 1 to 4 hours. An electric tape heater and a timer were used to perform the experiments. The adsorption temperature profile, adsorption rate and prototype performance have been analysed and discussed. The tested heating and desorption temperature of 100 °C and heating and desorption time of 1 to 4 hours was able to create a cooling effect of the cold chamber of the prototype of between -0.8 to 8.3 °C, which is adequate for vaccine storage requirement of 2 to 8 °C. The estimated Coefficient of Performance of the system ranges between 0.025 and 0. 076.

Synthesis of Reusable Cyclodextrin Polymers for Removal of Naphthol and Naphthylamine from Water

As one group of important naphthalene derivatives, naphthol and naphthylamine, are diffusely employed as dye intermediates. The presence of naphthol and naphthylamine in water systems may pose risks to the environment and public health due to their carcinogenicity. In this study, four mesoporous polymers prepared by β-cyclodextrin derivatives and tetrafluoroterephthalonitrile were obtained, and applied to deal with 1-naphthylamine, 2-naphthylamine, 1-naphthol, and 2-naphthol from water. The impact of adsorption time, initial concentration of naphthol and naphthylamine, and temperature on the adsorption efficiency of the four polymers were explored separately. The four polymers present fast adsorption kinetics towards naphthol and naphthylamine, attaining 93%~100% of adsorption equilibrium uptake for 1-naphthol, 1-naphthylamine, 2-naphthylamine in 15 min, and 87%~90% of equilibrium uptake for 2-naphthol in 15 min. The kinetics could be depicted well by the pseudo-second-order kinetic model. The adsorption isotherms of the four polymers towards naphthol and naphthylamine accord with Redlich-Peterson or Sips model. The adsorption ratio increases fast with reducing the initial concentration of naphthol and naphthylamine, which suggest that these polymers are applicable to removing low concentration of naphthol and naphthylamine from water. The adsorption ratio of naphthol and naphthylamine in 5 mg/L, can achieve over 95% in 25 oC. In addition, the four polymers can be effortlessly recovered by a gentle and simple washing procedure with little reduction in performance. The adsorption performance of the four polymers towards the four naphthalene derivatives can be improved by increasing the adsorption temperature. In conclusion, the prepared β-cyclodextrin polymers exhibit rapid water treatment in removing the four low-concentration naphthalene derivatives with convenient regeneration and good reusability.

Thermodynamic Studies on the Sorption of Lead (II), Chromium (III) and Manganese (II) ions onto Acid-Activated Shale

Shale mineral in its raw form was collected, processed, calcinated and activated using tetraoxosulphate (VI) acid. The microstructural arrangement and chemical composition of the raw, calcinated and acid-activated shale was determined using x-ray fluorescence and scanning electron microscope to verify its ability for the removal of Pb2+, Cr3+ and Mn2+ from wastewater. Batch experimental method was used to study the effect of different adsorption parameters on the sorption efficiency of shale. The effect of temperature on the sorption of Pb2+, Cr3+ and Mn2+ on acid-activated shale was investigated at varied temperature of 15 – 40 . The calculated value of enthalpy () was 12.50 kJ/mol for Pb2+ adsorption, 5 kJ/mol for Cr3+ and 11 kJ/mol for Mn2+ adsorption. The calculated values of Gibbs free energy () varies from -6.576 kJ/mol to 1.358 kJ/mol for Pb2+ adsorptions, from -2.696 kJ/mol to 0.192 kJ/mol for Cr3+ adsorptions, and -4.994 kJ/mol to 1.870 kJ/mol for Mn2+ adsorptions. The entropy () range is 38.68 – 60.946 kJ/mol for Pb2+ adsorptions, 16.69 – 24.58 kJ/mol for Cr3+ adsorptions, and 31.70 – 51.10 kJ/mol for Mn2+ adsorptions. The positive value of shows that the adsorption of Pb2+, Cr3+ and Mn2+ onto acid-activated shale was an endothermic process. The values of are negative at temperature of 298 K and above for the three metal ions studied, which confirmed that the adsorption of Pb2+, Cr3+ and Mn2+ on acid-activated shale was a spontaneous process. The decline in with increasing adsorption temperature showed that adsorptions of Pb2+, Cr3+ and Mn2+ onto acid-activated shale became better at higher temperature while the positive value of for all metal ions studied showed the amplified arbitrariness at the solid-solution interface during the fixation of the adsorbate on the active site of acid-activated shale.

N-enriched GO Adsorbent Series for Selective Adsorption of CO2: Characterization, Equilibrium, and Thermodynamic Studies

In this study a series of GO-based adsorbents were assembled via impregnation method using N-resources: 3-aminopropyl-triethoxysilane (APTS) as primary amio-silane, Piperazine (PIP) as secondary cyclic diamine, and ethanolamine (EA) as primary amine. The influence of amine type, adsorption temperature and pressure were undertaken to obtain the best CO2 adsorption performance. The characterizing techniques including FTIR, SEM, TGA, BET, BJH, and MP confirmed well impregnation of amine functionalities to the GO framework and high thermal stability of adsorbents. GO/APTS showed the maximum CO2 uptake (43.114 mmol/g) predicted by the Sips isotherm model and the highest CO2 ¬(15% V, balanced N2) selectivity (33.7 %) estimated by the ideal adsorbed solution theory. The experimental adsorption capacity of GO/APTS is 2.3 times higher than pristine GO. This behavior highlights the role of electron-donor amine and methyl groups and high molecular weight of APTS as well as high interfacial area of GO/APTS in CO2 capture.