Ting-ting Li

Grafting of β-cyclodextrin to magnetic graphene oxide via ethylenediamine and application for Cr(VI) removal.

A novel β-cyclodextrin (β-CD) polymer adsorbent named β-cyclodextrin/ethylenediamine/magnetic graphene oxide (CD-E-MGO) was synthesized for decontamination of Cr(VI) from aqueous solution. The sorption kinetics, isotherms and thermodynamics, as well as the effects of pH, aniline and ionic strength on the sorption process were investigated. The results indicated that CD-E-MGO could effectively remove Cr(VI) from aqueous solution and the sorption data could be well described by pseudo-second-order and Langmuir models. The intraparticle diffusion study indicated that intraparticle diffusion was not the only rate-limiting step. Thermodynamic parameters revealed that the sorption reaction was an endothermic and spontaneous process. The decontamination of Cr(VI) was influenced by solution pH and ionic strength. In the system with aniline, the Cr(VI) sorption was improved at low pH values but reduced at high pH values. These results are important for estimating and optimizing the removal of metal ions by CD-E-MGO composite.

Effect of porous zinc–biochar nanocomposites on Cr(VI) adsorption from aqueous solution

A new synthesis method was developed to produce zinc–biochar nanocomposites from sugarcane bagasse. The modified biochar maintained 1.2 to 2.0 times higher removal efficiency than that of pristine biochar. FTIR, XPS, BET and SEM were used to analyse the physical and chemical properties of the composite adsorbent. Batch sorption experiments were carried out to investigate the adsorption behavior of Cr(VI) by zinc–biochar. Experimental data were better fitted by a pseudo-second-order kinetics equation and the Freundlich isotherm model. Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic. The maximum adsorption of the modified biochar was observed at pH 2.0 with the sorption capacity of 102.66 mg g−1. The adsorbed zinc–biochar could be effectively regenerated by 0.5 mol L−1 NaOH solution and the adsorption ability decreased from 84.16 to 59.75 mg g−1 in the sixth cycle. In conclusion, the porous zinc–biochar showed great potential advantages in the removal of Cr(VI) from wastewater.

Chitosan modification of magnetic biochar produced from Eichhornia crassipes for enhanced sorption of Cr(VI) from aqueous solution

In this research, chitosan modification of magnetic biochar (CMB) was successfully prepared for effective removal of Cr(VI). Moreover, this study highlighted that the conversion of Eichhornia crassipes into biochar was a promising method for improved management of this highly problematic invasive species. The sorption kinetics, isotherms, thermodynamics, the effects of pH, and background electrolyte on the sorption process were investigated. The results indicated that CMB adsorbed more Cr(VI) (120 mg g−1) than that of pristine biochar (30 mg g−1). The sorption data could be well illustrated by pseudo-second-order and Langmuir models. Furthermore, thermodynamic parameters revealed that the sorption reaction was an endothermic and spontaneous process. The adsorption of Cr(VI) was influenced by solution pH and the maximum sorption capacity was achieved at pH 2. The background electrolyte PO43− and SO42− restricted the Cr(VI) sorption. These results are significant for exploring and optimizing the removal of metal ions by the CMB composite.

Adsorption behavior of Cr(VI) from aqueous solution onto magnetic graphene oxide functionalized with 1,2-diaminocyclohexanetetraacetic acid

A novel magnetic composite adsorbent was synthesized by grafting 1,2-diaminocyclohexanetetraacetic acid to magnetic graphene oxide (DCTA/E/MGO). The DCTA/E/MGO was employed for removing Cr(VI) from aqueous solution in this study. The composite was characterized by FESEM, TEM, BET, XRD, FT-IR and XPS. The adsorption behaviors of Cr(VI) by DCTA/E/MGO in aqueous solution were systematically investigated. Second order kinetic and Freundlich isotherm models validated the experimental data. The adsorption rate was influenced by both film diffusion and intraparticle diffusion. Thermodynamic parameters revealed that the adsorption reaction was an endothermic and spontaneous process. The novel adsorbent exhibited better Cr(VI) removal efficiency in solutions with low pH. The decontamination of Cr(VI) by DCTA/E/MGO was influenced by ionic strength. These results are important for estimating and optimizing the removal of metal ions by the DCTA/E/MGO composite.

Effect of aniline on cadmium adsorption by sulfanilic acid-grafted magnetic graphene oxide sheets

Cd(II) has posed severe health risks worldwide. To remove this contaminant from aqueous solution, the sulfanilic acid-grafted magnetic graphene oxide sheets (MGOs/SA) were prepared and characterized. The mutual effects of Cd(II) and aniline adsorption on MGOs/SA were studied. The effects of operating parameters such as pH, ionic strength, contact time and temperature on the Cd(II) enrichment, as well as the adsorption kinetics and isotherm were also investigated. The results demonstrated that MGOs/SA could effectively remove Cd(II) and aniline from the aqueous solution and the two adsorption processes were strongly dependent on solution pH. The Cd(II) adsorption was reduced by the presence of aniline at pH<5.4 but was improved at pH>5.4. The presence of Cd(II) diminished the adsorption capacity for aniline at pH<7.8 but enhanced the aniline adsorption at pH>7.8. The decontamination of Cd(II) by MGOs/SA was influenced by ionic strength. Besides, the adsorption process could be well described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that the intraparticle diffusion was not the only rate-limiting step for the adsorption process. Moreover, the experimental data of isotherm followed the Freundlich isotherm model.

Synthesis of graphene oxide decorated with core@double-shell nanoparticles and application for Cr(VI) removal

A novel graphene oxide composite, namely Fe3O4@SiO2@ chitosan/GO nanocomposite (MSCG) was synthesized for decontamination of Cr(VI) from aqueous solution. High-resolution transmission electron microscopy revealed a core@double-shell structure of the nanoparticles with iron oxide as the core, silica as the inner shell and chitosan as the outer shell. The characteristic results of Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and X-ray diffraction (XRD) showed that the Fe3O4@SiO2@chitosan particles were successfully assembled on the surface of the GO layers. The adsorption kinetics followed the pseudo-second-order model and the novel MSCG adsorbent exhibited better Cr(VI) removal efficiency in solutions at low pH. Thermodynamic parameters revealed that the sorption reaction was endothermic and spontaneous. Moreover, the adsorption capacity was about 90% of the initial saturation adsorption capacity after being used four times. By using a permanent magnet, the recycling process of both the MSCG adsorbents and the adsorbed Cr(VI) is more economically sustainable. These results suggest that MSCG is a potential and suitable candidate for the preconcentration and separation of Cr(VI) from wastewater and for the deep-purification of polluted water.

Tartaric acid modified Pleurotus ostreatus for enhanced removal of Cr( vi ) ions from aqueous solution: characteristics and mechanisms

Pleurotus ostreatus was modified by tartaric acid and used as a biosorbent for the removal of Cr(VI) from aqueous solution. The removal efficiency of Cr(VI) by the modified P. ostreatus was 2 to 2.5 times higher than by pristine P. ostreatus. FTIR and XPS analysis indicated that carboxyl and amino groups were the major functional groups for Cr(VI) sorption. Batch sorption experiments were carried out to investigate the characteristic adsorption behavior of MPOD. Experimental data fitted a pseudo-second order equation and the Freundlich isotherm. The optimum biosorption was observed at pH 2.0 with the biosorption capacity was 99.66 mg g−1. Thermodynamic analysis showed that the adsorption process was spontaneous and endothermic. The present results confirmed that electrostatic attraction and complexation were involved in Cr(VI) removal. Modified P. ostreatus has the characteristics of simplicity and obvious effects for the removal of Cr(VI) ions from aqueous solution.

Synthesis and adsorption application of amine shield-introduced-released porous chitosan hydrogel beads for removal of acid orange 7 from aqueous solutions

An effective and low-cost adsorbent named amine shield-introduced-released porous chitosan hydrogel beads (APCB) was synthesized and characterized by SEM, EDX, FTIR, XPS and the zeta potential. SEM images showed the porous structure of APCB and EDX analysis proved the adsorption behavior of Acid Orange 7 (AO7) onto APCB. FTIR analysis indicated that the amine-shield-release process and amine-introduce process both increased the amount of amine groups. XPS analysis confirmed the chemical compositions of the APCB. Zeta potential analysis indicated that the pHpzc of APCB was 5.4. The significance of this work was illustrated by the excellent adsorption capacity towards AO7. The maximum adsorption was observed at pH 2.0 with the adsorption capacity of 2803.77 mg g−1. APCB showed low adsorption capacity in high pH values and exhibited better AO7 adsorption capacity in low ionic strength solutions. Experimental data were well fitted by a pseudo-second-order kinetic model and Langmuir isotherm model. Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic.