Polymerization-based oxidation processes have emerged as a low-carbon-water purification technology for removing organic pollutants. Permanganate (Mn(VII)) can oxidize phenolic pollutants through polymerization; however, this process is currently challenged by the generation of soluble oligomers, resulting in low total organic carbon (TOC) removal and undesired byproducts in effluents. Herein, we demonstrated that incorporating carbon nanotubes (CNTs) into the Mn(VII) system effectively regulated phenol polymerization from soluble oligomers to insoluble multimers, remarkably enhancing TOC removal from 0.5% to 82.0% within 30 min. This remarkable enhancement originated from a synergetic mechanism involving interfacial enrichment and accelerated electron transfer, which promoted the generation of phenoxy radicals and their collisions with phenol and oligomers, thereby driving the polymer chain growth. These synergistic effects overcame the kinetic and steric limitations of the homogeneous Mn(VII) system during phenol oxidation. Quantitative structure-activity relationship analysis revealed the defect-rich and hydrophobic CNTs maximized the above-mentioned synergistic effect, while excessive carboxy contents suppressed phenol polymerization by increasing surface polarity and electrostatic repulsion. Overall, this work provided a simple yet facile strategy for regulating the polymerization products of phenolic pollutants in the Mn(VII) oxidation system, offering fundamental insights for the development of low-carbon and sustainable water treatment technology.
Most proposals for mitigating climate change assume that economic demand should grow without constraints so depend primarily on technology innovations to substitute today's activities with emissions-free alternatives. However, the potential for such "invisible technology substitutions", which could allow high-resource lifestyles to continue unchanged, is often overstated and disguised by burden-shifting. For example, plans may depend on synthetic fuels without accounting for its supply, or on negative emissions technologies without accounting for their power or land area requirements. Here, we show that all net-zero plans depend fundamentally on three resources: emissions-free electricity, biomass, and carbon storage. Using a comprehensive calculator, we reveal the high risk of shortages of these fundamental resources by comparing aggregated demands of net-zero plans, published by business, government, and industry bodies, against likely global availability in 2050. The calculator builds on physical models of 170 processes derived from an extensive literature search. Our results demonstrate that most climate policy proposals, which depend primarily on "invisible technology substitutions", require an improbable expansion of the fundamental resources in the time available, indicating significant risks of under-delivery. We demonstrate an alternative mitigation plan built on a credible forecast of resource availability, revealing overlooked opportunities for innovations in policy, service supply, and financing: feasible zero-emission futures necessitate end-user participation and changed economic demand, which are largely disregarded in current international policy discussions.
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