title: Biosorption of heavy metal ions onto agricultural residues buckwheat hulls functionalized with 1-hydroxylethylidenediphosphonic acid.
abstract: Novel biosorbent materials obtained from agricultural residues buckwheat hulls (BH) were successfully developed through functionalization with 1-hydroxylethylidenediphosphonic acid (HEDP), and they were characterized. This paper reports the feasibility of using HEDP-BH for removal of heavy metals from stimulated wastewater, the experimental results revealed that the adsorption property of functionalized buckwheat hulls with 120 mesh 120-HEDP-BH for Au(III) was very excellent, and the monolayer maximum adsorption capacity for Au(III) calculated from the Langmuir isotherm models was up to 450.45 mg/g at 35 °C. The combined effect of initial solution pH, 120-HEDP-BH dosage, and initial Au(III) concentration was investigated using response surface methodology (RSM), and the result showed that biomass dosage exerted a stronger influence on Au(III) uptake than those of initial pH and initial Au(III) concentration. Analysis of variance (ANOVA) of the quadratic model demonstrated that the model was highly significant. Moreover,  investigation on the adsorption selectivity showed that 120-HEDP-BH displayed strong affinity for gold in  aqueous solutions and even exhibited 100% selectivity for Au(III) ions in the presence of Zn(II) and Co(II). Regeneration capacities of 120-HEDP-BH were studied  using the eluent solutions of 0.0-5.0% thiourea in 0.1 mmol/L HCl, and it was found that the adsorption capability remains high after several cycles of adsorption-desorption process.
authors.affiliation: School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China. yinping426@163.com
authors.forename: Ping
authors.initials: P
authors.lastname: Yin
authors.forename: Zengdi
authors.initials: Z
authors.lastname: Wang
authors.forename: Rongjun
authors.initials: R
authors.lastname: Qu
authors.forename: Xiguang
authors.initials: X
authors.lastname: Liu
authors.forename: Jiang
authors.initials: J
authors.lastname: Zhang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xu
mesh_terms: D000327:Adsorption; D000383:Agriculture; D012968:Etidronic Acid / Q000737:chemistry*; D019612:Fagopyrum / Q000737:chemistry*; D006046:Gold / Q000302:isolation & purification; D007220:Industrial Waste / Q000032:analysis; D019216:Metals, Heavy / Q000737:chemistry* / Q000302:isolation & purification; D008855:Microscopy, Electron, Scanning; D008958:Models, Molecular; D012639:Seeds / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D019216:Metals, Heavy; D006046:Gold; D012968:Etidronic Acid