Synthesis of novel adsorbent by intercalation of biopolymer in LDH for the removal of arsenic from synthetic and natural water

This study focuses on the synthesis of nanocomposites named CCA and CZA that were prepared by the incorporation of cellulose(CL) in the Ca/Al and Zn/Al layered double hydroxide(LDH),respectively.These materials were then used for the uptake of As(Ⅲ)and As(V) from aqueous medium.Characterization of both nanocomposites(CCA and CZA) was done using FTIR and Raman analysis to identify the functional groups, N_2 adsorption-desorption isotherms to determine the specific surface area and pore geometry and XPS analysis to obtain the surface atomic composition.Some other characters were investigated using simultaneous TGA and DTA and elemental chemical analysis(CHNS/O).The crystallinity of the prepared nanocomposites was displayed by XRD patterns.Furthermore,the sheet-like structure of the LDHs and the irregularity of surface morphology with porous structure were observed by TEM and SEM microphotographs.Optimization of maximum adsorption capacity was adjusted using different parameters including pH,contact time and adsorbent dosage.The pseudo-second-order model was in good fitting with kinetics results.The adsorption isotherm results showed that CZA exhibits better adsorption capacity for As(Ⅲ) than CCA and the Langmuir isotherm model described the data well for both nanocomposites.Thermodynamic studies illustrated the endothermic nature of CCA and exothermic nature on CZA,as well as the fact that the adsorption process is spontaneous.A real water sample collected from well located in Gabes(Tunisia),has also been treated.The obtained experimental results were confirmed that these sorbents are efficient for the treatment of hazardous toxic species such as.     

Functionalized CMK-3 mesoporous carbon with 2-amino-5-mercapto-1,3,4-thiadiazole for Hg(II) removal from aqueous media

Ordered mesoporous carbon（CMK-3） was synthesized and functionalized with 2-amino-5-mercapto-1,3,4-thiadiazole groups（AMT-OCMK-3） for Hg（Ⅱ） removal from aqueous solution. The modified CMK-3 was characterized by X-ray diffraction, N2adsorption-desorption isotherm, scanning electron microscopy and Fourier transform infrared spectroscopy. The effects of solution pH, contact time, initial Hg（Ⅱ） concentration and matrix effect were studied. The adsorption data were successfully fitted with the Langmuir model, exhibiting high adsorption capacity of 450.45 mg/g of AMT-OCMK-3. In the solid-phase extraction system a series of experimental parameters such as sample flow rate, sample volume,eluent volume and concentration of the eluent solution have been investigated and established for preconcentration of Hg（Ⅱ） in aqueous solution. The results showed that the enrichment factor for Hg（Ⅱ） was 250, the precision（relative standard deviation（RSD）, %） for six replicate measurements was 2.05% and the limit of detection for Hg（Ⅱ） was achieved at0.17 μg/L.     

Response surface method for modeling the removal of carbon dioxide from a simulated gas using water absorption enhanced with a liquid-film-forming device

This paper presents the results from using a physical absorption process to absorb gaseous CO_2mixed with N_2using water by producing tiny bubbles via a liquid-film-forming device(LFFD)that improves the solubility of CO_2in water.The influence of various parameters—pressure,initial CO_2concentration,gas-to-liquid ratios,and temperature—on the CO_2removal efficiency and its absorption rate in water were investigated and estimated thoroughly by statistical polynomial models obtained by the utilization of the response surface method(RSM)with a central composite design(CCD).Based on the analysis,a high efficiency of CO_2capture can be reached in conditions such as low pressure,high CO_2concentration at the inlet,low gas/liquid ratio,and low temperature.For instance,the highest removal efficiency in the RSM–CCD experimental matrix of nearly 80%occurred for run number 20,which was conducted at 0.30 MPa,CO_2concentration of 35%,gas/liquid ratio of 0.71,and temperature of 15°C.Furthermore,the coefficients of determination,R~2,were 0.996 for the removal rate and 0.982 for the absorption rate,implying that the predicted values computed by the constructed models correlate strongly and fit well with the experimental values.The results obtained provide essential information for implementing this method properly and effectively and contribute a promising approach to the problem of CO_2capture in air pollution treatment.     

Simultaneous removal of SO2 and NO using a spray dryer absorption (SDA) method combined with O3 oxidation for sintering/pelleting flue gas

Based on the demand of sintering/pelleting flue gas ultra-low emission,a semi-dry method using a spray dryer absorber (SDA) combined with O₃ oxidation was proposed for simultaneous removal of SO₂ and NO.Effects of O₃ injection site,O₃/NO molar ratio,and spray tower temperature on the removal efficiencies were investigated.It was revealed that both desulfurization and denitrification efficiencies could reach to 85%under the conditions of setting O_3...     

Chemically modified silica gel with 1-{4-[(2-hydroxy-benzylidene)amino]phenyl}ethanone: Synthesis, characterization and application as an efficient and reusable solid phase extractant for selective removal of Zn(II) from mycorrhizal treated fly-ash samples

1-{4-[(2-hydroxy-benzylidene)amino]phenyl}ethanone functionalized silica gel was synthesized and used as a highly efficient, selective and reusable solid phase extractant for separation and preconcentration of trace amount of Zn(II) from environmental matrices. The adsorbent was characterized by fourier transform infrared spectroscopy (FT-IR), elemental analysis,¹³C CPMAS NMR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and BET surface area analysis. The dependence of zinc extraction on various analytical parameters such as pH, type and amount of eluent, sample flow rate and interfering ions were investigated in detail. The material exhibited superior adsorption efficiency for Zn(II) with high metal loading capacity of 1.0 mmol/g under optimum conditions. After adsorption, the recovery (> 98%) of metal ions was accomplished using 1.0 mol/L HNO₃ as an eluent. The sorbent was also regenerated by microwave treatment in milder acidic environment (0.1 mol/L HNO₃). The lower detection limit and preconcentration factor of the present method were found out to be 0.04 μg/L and 312.5 respectively. The modified silica surface possessed excellent selectivity for the target analytes and the adsorption/desorption process remained effective for at least ten consecutive cycles. The optimized procedure was successfully implemented for the extraction of Zn(II) from mycorrhizal treated fly ash and pharmaceutical samples with reproducible results.