Yu Jingang

Removal of vanadate anion by calcined Mg/Al-CO3 layered double hydroxide in aqueous solution

Abstract Mg/Al-CO3 layered double hydroxide (LDH2) with Mg(II): Al(III) molar ratio of 2:1 was synthesized by co-precipitation method and its calcined product Mg2Al-CLDH(CLDH2) was prepared by heating Mg2Al-LDH at 773 K for 6 h. Removal of vanadate anion ( VO 4 3 − ) from aqueous solution on CLDH2 was studied. Batch studies were carried out to address various experimental parameters such as Mg/Al molar ratio, adsorbent dosage, initial concentration of solution, contact time and temperature. Vanadate was removed effectively at the optimized experimental conditions. The adsorption kinetics data fitted the pseudo-first-order model. Isotherms for adsorption vanadate by CLDH2 at different solution temperatures were well described using the Langmuir and Freundlich equations, and the isotherm parameters were calculated using linear regression analysis. The adsorption data fitted the langmuir model with good values of the correlation coefficient (R2>0.999). The negative value of ΔGΘ and the positive value of ΔHΘ indicate that the adsorption processes are spontaneous endothermic in nature. The mechanism of adsorption suggests that the surface adsorption is the main process.

Adsorption of glutamic acid from aqueous solution with calcined layered double Mg–Fe–CO3 hydroxide

Abstract Layered double Mg–Fe–CO 3 hydroxide (Mg–Fe–LDH) with a mole ratio of Mg to Fe of 3 was synthesized by coprecipitation method and calcined product Mg–Fe–CLDH was obtained by heating Mg–Fe–LDH at 500 °C for 6 h. The as prepared Mg–Fe–LDH and calcined Mg–Fe–CLDH were used for removal of glutamic acid (Glu) from aqueous solution, respectively. Batch studies were carried out to address various experimental parameters such as contact time, pH, initial glutamic acid (Glu) concentration, co-existing anions and temperature. Glu was removed effectively (99.9%) under the optimized experimental conditions with Mg–Fe–CLDH. The adsorption kinetics follows the Hos pseudo second-order model. Isotherms for adsorption with Mg–Fe–CLDH at different solution temperatures were well described using the Langmuir model with a good correlation coefficient. The intraparticle diffusion model fitted the data well, which suggests that the intraparticle diffusion is not only the rate-limiting step.

Preparation and characterization of MWCNTs/LDHs nanohybrids for removal of Congo red from aqueous solution

Abstract The assembly of layered double hydroxides (LDHs) and multi-walled carbon nanotubes (MWCNTs) nanohybrids was prepared as MWCNTs/LDHs by co-precipitation. The synthesized nanoparticles were characterized by using XRD, FT-IR, SEM/EDX, TGA and BET. XRD and SEM studies proved that MWCNTs phases did not enter into the interlayers of LDHs, they dispersed over the LDHs surface homogeneously. BET results showed that MWCNTs/LDHs possessed hierarchically porous nanostructure with large surface area (124.974 m2/g) and great pore volume (0.604 cm3/g). Batch experiments were conducted to study the adsorption efficiency of Congo red (CR). It was worthy to note that MWCNTs/LDHs exhibited excellent adsorption performance with the maximum CR adsorption capacity of 595.8 mg/g in weak acidic environment. The adsorption kinetics and isotherm parameters can be well described by the pseudo-second-order and the Langmuir isotherm models, respectively. The thermodynamic studies indicated that the adsorption process was spontaneous and endothermic.

Effective removal of brilliant green from aqueous solution with magnetic Fe3O4@SDBS@LDHs composites

Abstract The magnetic composite-materials (Fe3O4@SDBS@LDHs) were prepared by sodium dodecyl benzene sulfonate (SDBS) modified layered double hydroxides (SDBS@LDHs) with Fe3O4 via co-precipitation method. The results of XRD, FT-IR and SEM/EDS indicated that the dispersibility of LDHs was improved, and the modification of SDBS took place on the surface of LDHs. The adsorption capacity of Fe3O4@SDBS@LDHs to brilliant green (BG) reaches 329.1 mg/g after the adsorption equilibrium. The thermodynamic parameters indicated that the adsorption process was endothermic and spontaneous, and the rate of a reaction increased with the raise of the reaction temperature. The Langmuir model was applicable for describing the sorption isotherms, indicating that the adsorption process is a monolayer adsorption. The results of kinetics study showed that adsorption fitted the pseudo-second order model well. The adsorbents still have good adsorption performance after four adsorption cycles. Moreover, the magnetic composite could be easily separated from aqueous solution. This indicated that Fe3O4@SDBS@LDHs can be considered as potential adsorbents in environmental applications for the removal of BG from aqueous solutions.