This paper proposes an integrated coupling process of alkali leaching, HBTA-TOPO synergistic extraction, and carbonation for the resource utilization of spent carbon anode (SCA), a typical lithium-bearing industrial solid waste from electrolytic aluminum production, whose lithium content exceeds the ore grade. Compared with conventional acid leaching methods, the adopted alkaline leaching approach features mild reaction conditions, low equipment corrosion risk, and eliminates the volatilization of toxic hydrogen fluoride (HF) gas, thus showing prominent environmental safety advantages. Under the optimal alkaline leaching conditions (NaOH concentration of 10 mol/L, reaction temperature of 90 °C, liquid-to-solid ratio of 10:1, and reaction time of 120 min), the maximum Li+ leaching rate reaches 89.46%. As the leaching process proceeds, lithium in the carbon slag rapidly migrates to the alkaline leaching solution. The Na–Al–F bonds of cryolite (Na3AlF6) and lithium cryolite (Na2LiAlF6) present in the SCA gradually break, and soluble ions such as Na+, Li+, Al3+, and F− enter the solution. High-concentration Na+ reacts with free F− to form sodium fluoride (NaF), which adheres to the SCA, leading to an increase in the sodium-aluminum ratio (Na/Al) of the SCA. The HBTA-TOPO synergistic extraction system is proposed for the extraction and enrichment of lithium in the lithium alkaline leaching solution, and the extraction residue is used to repair and regenerate cryolite. The extraction efficiency of Li+ reaches and the yield of cryolite reaches 81.54% and 76.54%. The molecular ratio of sodium fluoride to aluminum fluoride in synthetic cryolite products is relatively high. This integrated process realizes the efficient recovery of lithium and the high-value regeneration of cryolite from SCA, providing a sustainable technical route for the clean utilization of electrolytic aluminum solid waste. This integrated closed-loop process realizes the simultaneous recovery of lithium and high-value regeneration of cryolite from SCA, which not only mitigates the environmental pollution caused by SCA stacking and the scarcity of lithium resources, but also provides a sustainable technical route for the clean and high-value utilization of electrolytic aluminum solid waste.
In recent years, visible-light-induced transformations have taken a central role in driving forward the progress of modern organic synthesis. Despite the abundance of synthetic strategies enabling access to aryl- and alkyl-centered radicals, the exploitation of photochemistry to generate highly reactive alkenyl radicals has remained notably underdeveloped. Herein, we report a sustainable strategy for generating alkenyl radicals based on a photocatalytic single-electron transfer process. Through systematic optimization of conditions such as photocatalysts, light sources, and additives, we confirmed that radical reactions can efficiently occur under metal-free conditions using styrenylthiophene salt as radical donors, thiuram derivatives as radical acceptors, and 4CzIPN (1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene) as the photocatalyst. This method is operationally simple, environmentally friendly, and does not require the addition of precious metal reagents, providing a novel strategy for the methodology of alkenyl radical generation.
Solvents dominate mass input, energy demand, and environmental impact in pharmaceutical manufacturing, yet solvent selection and recovery are often evaluated using fragmented or non-comparable metrics. Here, we present a solvent-centric sustainability framework that integrates mass-based indicators with life-cycle and energy metrics to enable transparent comparison of conventional and redesigned solvent systems. The framework harmonizes Process Mass Intensity (PMI), circular PMI (cPMI), Global Warming Potential (GWP), and Cumulative Energy Demand (CED) within consistent cradle-to-gate system boundaries, supported by literature-derived data, machine-learning (ML) models, and digital-twin–based sustainability assessment tools. The methodology is demonstrated using Sertraline as a representative solvent-intensive active pharmaceutical ingredient (API). A simplified, literature-based synthesis route contextualizes solvent use across key reaction and isolation steps. Targeted solvent substitutions—most notably replacement of tetrahydrofuran, chlorinated solvents, and dipolar aprotic media with 2-methyltetrahydrofuran and ethanol-based systems—are evaluated alongside enhanced solvent recovery and catalytic hydrogenation. Relative to the solvent-dominant subsequence of the synthesis (PMI ≈ 78 kg·kg−1 API), for which detailed solvent mass-balance data are available, the redesigned solvent strategy reduces PMI to approximately 45 kg·kg−1 API, achieves a cPMI of 6–10 at ≥80% solvent recovery, and consistently decreases GWP and CED. By explicitly mapping solvent redesign outcomes to the 12 Principles of Green Chemistry, this study demonstrates how solvent-focused interventions, supported by predictive digital tools with excellent agreement between modelled and empirical trends, can deliver substantial sustainability improvements without modifying the underlying synthetic route or relying on proprietary process data. While not intended as an industrial benchmark, the Sertraline case study illustrates how harmonized metrics, life-cycle thinking, and AI-enabled digital assessment can support evidence-based solvent selection and sustainability-oriented process development in API manufacturing.
