The use of living plants to recover precious metals with potential catalytic activity is still at the infant stage. In this study, selective hydrogenation of furfural to furfuryl alcohol using novel bio-ore catalysts recovered from the end stage of phytomining process is demonstrated. The phytomining process was carried out in the green house by artificially contaminating cassava (Manihot esculenta) plant with 500 mg/L palladium (Pd) and platinum (Pt) solutions for a period of eight weeks. After harvesting, concentrations of metals as high as 78 ± 0.047 and 1276 ± 0.036 µg/g of Pd and Pt, respectively, were detected in the calcinated root of cassava. The produced bio-ore catalysts; @PdCassCat and @PtCassCat were fully characterized with the following techniques: transmission electron microscopy (TEM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), powder X-ray diffraction (pXRD), N2-sorption, and UV-visible spectroscopy techniques and directly applied as catalysts for hydrogenation of furfural to furfuryl alcohol. The reaction was conducted under an optimized condition (furfural (10 mmol), triethylamine (Et3N) (10 mmol), formic acid (20 mmol), temperature (160 °C), catalyst amount (40 mg)) realizing a yield of 76.5% and 100% furfuryl alcohol using @PdCassCat and @PtCassCat, respectively. The catalytic activities of the @PdCassCat and @PtCassCat were excellent as well as recyclable up to four and five times, respectively.

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In this work, we have demonstrated for the first time that a cyanogen-glucoside-rich cassava plant (Manihot esculenta) is highly efficient in phytoextraction (up to 88%) of nickel to obtain a type of bio-ore comprising Ni nanoparticles (NPs) supported on the recovered plant material. Up to 1251 ppm was extracted from low Ni concentration soil by the cassava plant, as was measured by flame atomic absorption spectrometry. The bio-ore was used as a resource for preparing a heterogeneous catalyst (Ni@CassCat), in which Ni NPs are supported on mesoporous biochar following a calcination step. Ni@CassCat was characterized using high-resolution transmission electron microscopy with energy-dispersive X-ray, scanning electron microscopy with energy-dispersive X-ray, powder X-ray diffraction, N2-sorption techniques, and ultraviolet–visible spectrometry. Subsequently, Ni@CassCat was used as a heterogeneous catalyst to hydrogenate carbon dioxide (CO2) to formate with a turnover number of 485. Furthermore, the recyclability of Ni@CassCat was demonstrated. This work demonstrates a two-pronged approach to sustainability, transforming two waste streams (mine tailings and CO2) to value.