In the phytomining (phytoextraction) of nickel from low-grade ores, hyperaccumulator plants are grown to concentrate nickel ions in their above-ground biomass. To improve the efficiency and sustainability of the extraction process, engineers must select the most viable chemical pathway to recover pure nickel metal from the harvested crops.
Which sequence of processes correctly describes the standard chemical pathway for obtaining pure nickel metal from the harvested biomass?
Anaerobic digestion of the wet biomass to yield a nickel-rich digestate, followed by direct thermal reduction with carbon monoxide.
Pyrolysis of the dry biomass at 1200∘C1200^\circ\text{C}1200∘C to directly vaporize metallic nickel, followed by condensation under a nitrogen atmosphere.
Combustion of the biomass to produce a concentrated ash, followed by leaching with dilute sulfuric acid, and subsequent electrolysis of the resulting solution.
Direct mechanical pressing of the wet biomass to extract a nickel-rich sap, followed by displacement precipitation using scrap iron.
81 exam-style questions on OCR GCSE Chemistry Improving processes and products. Each one has a worked solution and a mark scheme showing where the marks go.