Haixin Xia,Yaohong Zhang,Qian Chen,Renrong Liu,Hai Wang
Two functionalized biochar composites (ZF@CBC and SZF@CBC) were fabricated and applied for capturing Pb(II) and Cd(II) from wastewater. SZF@CBC were achieved by loading Zn/Fe nanoparticles (NPs) and coating starch onto corn cobs biochar (CBC) surface, while ZF@CBC was realized by loading Zn/Fe NPs onto CBC surface. The characterization analysis (SEM-EDS, XRD and FTIR) revealed that Zn/Fe NPs and starch were successfully introduced onto CBC surface. The adsorption data of Pb(II) and Cd(II) by ZF@CBC and SZF@CBC conformed to the model of pseudo second order kinetic and Langmuir isothermal and the capture Pb(II) and Cd(II) was a chemisorption process. The maximum sorption capacities of SZF@CBC for Pb(II) and Cd(II) reached 199.98 mg/g and 183.93 mg/g, which were 3.37 and 3.84 times high as that of CBC, respectively. Due to the presence of plentiful exposed adsorption sites (–OH, –COOH, Zn-O and Fe-O) on SZF@CBC surface, which endowed it to accelerate Pb(II) and Cd(II) adsorption. In addition, complexation, electrostatic attraction, ion exchange and physical adsorption took part in the adsorption process. Besides, SZF@CBC still exhibited very good removal capacity for Pb(II) and Cd(II) even in the coexistence of multiple interfering ions and maintained stable adsorption capacity after five consecutive cycles. Therefore, SZF@CBC could be used as an excellent adsorbent for decontaminating Pb(II) and Cd(II) from wastewater with multiple pollutants, and also could be used in resource utilization of biomass waste, which possessed potential applications prospects.
Yingying Wang,Fuyu Zhang,Mengshuo Du,Bihe Chen,Yifeng Xu,Wenzhi Tang,Zhonghong Li
Highly toxic Pb(Ⅱ) and Cd(Ⅱ) persist in water and soil, disrupting ecosystems while threatening human health through bioaccumulation. Metal-organic frameworks (MOFs) as adsorbents toward heavy metal ions have garnered significant research attention. However, their adsorption capacity and retrieval are limited by small pore size and powder form. Herein, we designed a defective MIP-202 composite aerogel (DMCA) to efficiently remove Pb(Ⅱ) and Cd(Ⅱ). Mixed ligand (mercaptosuccinic acid) and modulator (butyric acid) were involved in the synthesis of MIP-202, and competed with the original amino acid ligand for binding to Zr clusters leading to the disruption of the original structure of MIP-202 and defect formation. Defective MIP-202 (D-MIP-202) possessed larger BET surface area (from 35.79 to 129.57 m 2 /g) and pore size (from 6.16 to 11.78 nm). Moreover, D-MIP-202 powder and sodium alginate were synthesized into DMCA with abundant adsorption sites and porous structures to enhance the sorption capacities, which were 434.7 mg/g (Pb(II)) and 202.6 mg/g (Cd(II)). The adsorption process primarily occurs on the heterogeneous surface of the material and represents a spontaneous chemisorption behavior. The adsorption mechanism is attributed to chelation, and ion exchange. This study presents an effective strategy for the remediation of heavy metal ions in aqueous systems.
Ni Tang,Xue Liu,Meng-Ru Jia,Xin-Yao Shi,Jing-Wei Fu,Dong-Xing Guan,Lena Q. Ma
In this study, a two-step functionalizing strategy by combining co-condensation with grafting procedures was employed to synthesize well-ordered Amino- and Thiol-Bifunctionalized SBA-15 (ATBS) mesoporous silica. Its physicochemical properties , performance, and mechanisms in immobilization of toxic metals Pb and Cd in water and soil were investigated. After bi-functionalization, X-ray diffractometer , transmission electron microscope , and N 2 adsorption-desorption measurements confirmed that the ATBS maintained a highly-ordered mesoporous structure, large surface area and pore volume. The elemental analysis, Fourier transform infrared spectroscopy and X-ray Photoelectron Spectroscopy (XPS) evidenced the successful incorporation of amine and thiol groups into ATBS. These structure and functional characteristics of ATBS benefited Pb and Cd sorption . Sorption isotherms of Pb and Cd were better fit with Sips and Redlich-Peterson models. Sorption kinetics suggested that Pb sorption was mainly regulated by chemical reactions, whereas both diffusion process and chemical reactions were rate-regulating steps in Cd sorption. ATBS showed the maximum sorption capacities for Pb and Cd at 120 and 38 mg g −1 , respectively. The sorption mechanisms revealed by XPS measurements suggested that Cd sorption was mainly attributed to thiol groups while Pb was efficiently bond to both thiol and amino groups. High and stable sorption efficiencies were attained in the pH range of 4–6, with a higher affinity towards Pb than Cd. Furthermore, its ability to immobilize Pb and Cd in soils was examined with an incubation experiment, which showed that ATBS reduced 30–56% of MgCl 2 -extractable Pb and Cd in a contaminated soil. The synthesized sorbent via the two-step functionalizing strategy shows high sorption efficiency towards Pb and Cd, and thus it has potential application in remediating Pb and Cd contaminated water and soils.
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