Abstract
The precious platinum group metals distributed in urban industrial products should be recycled because of their rapid decline in the contents through excessive mining. In this work, thiourea modified magnetic biocarbons are prepared via an energy-efficient microwave-assisted activation and assessed as potential adsorbents to recover platinum ions (i.e., Pt(IV)) from dilute waste solution. The physicochemical properties of prepared biocarbons are characterized by a series of spectroscopic and analytic instruments. The adsorption performance of biocarbons is carried out by using batch tests. Consequently, the maximum adsorption capacity of Pt(IV) observed for adsorbents is ca. 42.8 mg g−1 at pH = 2 and 328 K. Both adsorption kinetics and isotherm data of Pt(IV) on the adsorbents are fitted better with non-linear pseudo second-order model and Freundlich isotherm, respectively. Moreover, the thermodynamic parameters suggest that the Pt(IV) adsorption is endothermic and spontaneous. Most importantly, the adsorbents exhibit high selectivity toward Pt(IV) adsorption and preserve ca. 96.9% of adsorption capacity after six cyclic runs. After adsorption, the regeneration of the prepared adsorbents can be effectively attained by using 1 M thiourea/2% HCl mixed solution as an eluent. Combined the data from Fourier transform infrared and X-ray photoelectron spectroscopies, the mechanisms for Pt(IV) adsorption are governed by Pt–S bond between Pt(IV) and thiourea as well as the electrostatic attraction between anionic PtCl62− and cationic functional groups of adsorbents. The superior Pt(IV) recovery and sustainable features allow the thiourea modified magnetic biocarbon as a potential adsorbent to recycle noble metals from spent autocatalyst solution.
Highlights
The precious platinum group metals distributed in urban industrial products should be recycled because of their rapid decline in the contents through excessive mining
The physicochemical properties of Tu–N–spent coffee grounds (SCGs)–C–A were examined by various analytic methods [i.e., N2 adsorption–desorption isotherms and elemental analysis (EA)] and spectroscopies [i.e., X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR)]
The peak intensity of Fe3O4 observed for N–SCG–C–A is noticeably decreased after microwave-assisted N-doping process
Summary
The precious platinum group metals distributed in urban industrial products should be recycled because of their rapid decline in the contents through excessive mining. Thiourea modified magnetic biocarbons are prepared via an energy-efficient microwave-assisted activation and assessed as potential adsorbents to recover platinum ions (i.e., Pt(IV)) from dilute waste solution. The superior Pt(IV) recovery and sustainable features allow the thiourea modified magnetic biocarbon as a potential adsorbent to recycle noble metals from spent autocatalyst solution. Hydrometallurgy includes solvent extraction, precipitation and ion exchange that extract metals by c hemicals[10,11,12] These methods may suffer from the high cost, energy consumption and secondary pollution[13,14]. The biocarbons exhibit potential benefits in the environmental remediation, energy conversion and storage[28,29,30,31,32] due to their abundant functional groups, high mechanical and chemical stability and renewable sustainability. The objectives of this research were to (1) synthesize and characterize the prepared Tu–N–SCG–C–A with various techniques and evaluate its feasibility to act as an adsorbent in the recovery of Pt(IV) ions, (2) explore the adsorption kinetic, isotherm, thermodynamic studies of Pt(IV) ions and study the effects of adsorbent dosages, pH and competitive adsorption, (3) and identify the plausible adsorption mechanisms of Pt(IV) onto Tu–N–SCG–C–A
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