A mining corporation is evaluating green alternatives to traditional pyrometallurgical smelting for extracting transition metals from low-grade ores. They are comparing bioleaching using Acidithiobacillus ferrooxidans and phytomining using nickel-accumulating hyperaccumulators.
Which statement correctly identifies a key operational or environmental comparison between these two methods?
Bioleaching utilizes autotrophic bacteria to produce a highly alkaline leachate that precipitates metal hydroxides, whereas phytomining yields an acidic gaseous byproduct during plant transpiration.
Phytomining requires subsequent chemical processing (such as acid leaching of ash followed by electrolysis) to obtain the pure metal, whereas bioleaching directly precipitates pure elemental metal crystals during the bacterial digestion phase.
Bioleaching is highly suited for deep, anaerobic underground ore deposits due to the obligate anaerobic nature of the bacteria, whereas phytomining is restricted to the aerobic upper soil horizons.
Bioleaching produces an acidic leachate containing dissolved heavy metal ions that requires careful containment to avoid environmental runoff, whereas phytomining acts as a form of soil remediation while concentrating metals in harvestable biomass.
Practise OCR GCSE Chemistry Improving processes and products with exam-style questions for Foundation and Higher tier. 97 questions, matched to the OCR GCSE Chemistry (J248) specification and written in Paper 1 and Paper 2 (Foundation Tier) or Paper 3 and Paper 4 (Higher Tier) style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.