Ti3C2Tx MXene-生物炭異質結構對水-能源-資源連結的研究

Abstract

多重污染物廢水的同步修復以及養分回收以支持永續生質能源生產，仍然是水–能源–資源鏈結（water-energy-resource nexus）中的重大挑戰。本研究建立了一套整合性框架，結合 Ti3C2Tx MXene-生物炭（MB）異質結構用於多污染物廢水處理，並將富含養分之生物炭再利用於能源作物栽培與熱化學能量回收。透過超音波輔助合成，成功製備 MXene 與生物炭比例為 1:9、3:7 與 5:5 的 MB 複合材料。結構特性分析證實 Ti3C2Tx MXene 已成功嵌入生物炭基質中，並提升材料結晶性、表面紋理與表面官能基特性，同時使 MB_5:5 的氧含量由原始生物炭的 18.49% 降低至 7.33%。在最佳吸附條件下，MB 複合材料對多種無機污染物展現優異同步去除能力，其中 Cu、Fe 與 Pb 的去除率均超過 99%，Zn 達 98.28%，NH4+ 為 97.83%，PO43- 超過 97%。吸附行為以 Freundlich 等溫模式具有最佳擬合結果（R2 = 0.981-0.997），顯示 MB 表面具有異質吸附位點與多層吸附特性；同時，擬二級動力學模式（R2 ≈ 0.999）顯示吸附主要受化學吸附機制控制，包括靜電吸引、離子交換及表面錯合反應。熱力學分析進一步證實吸附過程具有自發性與吸熱特性，其表觀 Gibbs 自由能變化（ΔG）介於 -4.48 至 -25.96 kJ/mol，而焓變化（ΔH）最高達 61.69 kJ/mol。再生實驗結果顯示，MB 複合材料於多次循環後仍能維持相對穩定的吸附效能，顯示其具有良好的再利用潛力。 為建立循環式資源回收途徑，本研究進一步將廢水處理後所得之富養分生物炭應用於狼尾草（Pennisetum purpureum）栽培。生物炭改良後之生質材料展現較佳的理化性質、更高的高位熱值（HHV 最高達 17.43 MJ/kg），以及與芳香化程度提升與揮發分解行為改變相關之熱分解特性。等轉化率動力學分析顯示，不同處理條件會顯著影響熱轉化行為，其中 KAS 方法所得表觀活化能介於 33.08-65.07 kJ/mol，FWO 方法介於 44.36-116 kJ/mol，而 Kissinger 峰值法則介於 73.92-97.88 kJ/mol。熱裂解分析亦顯示可形成具熱穩定性的碳質殘餘物，具有再生能源回收與碳固定潛力。 採用 ReCiPe 2016 與 IPCC 2021 GWP100 方法之生命週期評估結果顯示，不同路徑具有明顯差異化的環境表現。在 ReCiPe 中點分析下，WW/BW 路徑可大幅降低與用水相關之人體健康衝擊，而再生生物炭路徑相較於對照組亦展現較低之化石資源耗竭與氣候負荷。在納入 CO2 吸收之 IPCC 2021 GWP100 架構下，對照組路徑呈現微幅正向淨氣候衝擊（1.04 × 10-2 至 1.09 × 10-2 kg CO2-eq/MJ），而再生生物炭路徑則轉變為淨負值（-2.77 × 10-2 至 -2.81 × 10-2 kg CO2-eq/MJ），反映在既定系統邊界下之氣候效益與化石資源替代效應。 整體而言，本研究建立了一套整合先進 MXene–生物炭吸附材料、廢水修復、養分循環、生質資源高值化、熱化學能量回收與生命週期永續評估之可擴展策略，並將其應用於水–能源–資源鏈結架構中。研究結果顯示，MXene–生物炭異質結構具有將廢水污染物轉化為高附加價值生質能源與環境資源之潛力，可進一步支持永續水資源管理、再生能源發展與氣候變遷減緩。

The simultaneous remediation of multi-contaminant wastewater and recovery of nutrients for sustainable bioenergy production remains a major challenge within the water-energy-resource nexus. This study developed an integrated framework combining Ti3C2Tx MXene-biochar (MB) heterostructures for multi-contaminant wastewater treatment with nutrient-enriched biochar reuse for bioenergy crop cultivation and thermochemical energy recovery. Ultrasound-assisted synthesis successfully produced MB composites with MXene-to-biochar ratios of 1:9, 3:7, and 5:5. Structural characterization confirmed effective incorporation of Ti3C2Tx MXene into the biochar matrix, resulting in enhanced crystallinity, surface texturing, and surface functionalization, while reducing oxygen content from 18.49% in pristine biochar to 7.33% in MB_5:5. The MB composites demonstrated high simultaneous removal efficiencies for multiple inorganic pollutants, achieving >99% removal of Cu, Fe, and Pb, 98.28% for Zn, 97.83% for NH4+, and >97% for PO43- under optimized adsorption conditions. Adsorption behavior was best described by the Freundlich isotherm model (R2 = 0.981-0.997), indicating heterogeneous adsorption sites and multilayer adsorption behavior, while pseudo-second-order kinetic modeling (R2 ≈ 0.999) suggested chemisorption-dominated uptake mechanisms involving electrostatic attraction, ion exchange, and surface complexation. Thermodynamic analysis further indicated spontaneous and endothermic adsorption behavior, with apparent ΔG values ranging from -4.48 to -25.96 kJ/mol and ΔH values up to 61.69 kJ/mol. Regeneration studies demonstrated relatively stable adsorption performance over repeated cycles, supporting the reusability potential of the MB composites. To establish a circular resource-recovery pathway, nutrient-enriched biochar derived from wastewater treatment was subsequently applied for cultivation of Pennisetum purpureum. Biochar-amended biomass exhibited improved physicochemical properties, enhanced higher heating value (HHV up to 17.43 MJ/kg), and altered thermal decomposition characteristics associated with increased aromaticity and modified devolatilization behavior. Iso-conversional kinetic analyses demonstrated that thermal conversion behavior varied substantially with treatment condition, with apparent activation energies ranging from 33.08 to 65.07 kJ/mol by the KAS method and from 44.36 to 116 kJ/mol by the FWO method, while Kissinger peak-based activation energies ranged from 73.92 to 97.88 kJ/mol. Pyrolysis analyses further indicated the formation of thermally stable carbonaceous residues with potential for renewable energy recovery and carbon stabilization. Life cycle assessment using ReCiPe 2016 and IPCC 2021 GWP100 methodologies revealed pathway-dependent environmental performance. Under ReCiPe midpoint analysis, the WW/BW pathway substantially reduced water-consumption-related human health impacts, while recovered biochar pathways demonstrated lower fossil resource scarcity and reduced climate burdens compared with control systems. Under the IPCC 2021 GWP100 framework including CO2 uptake, control pathways showed small positive net climate impacts (1.04 × 10-2 to 1.09 × 10-2 kg CO2-eq per MJ), whereas recovered biochar pathways shifted to net-negative values (-2.77 × 10-2 to -2.81 × 10-2 kg CO2-eq per MJ), reflecting accounting-based climate benefits and fossil resource displacement within the defined system boundaries. This study establishes an integrated and scalable strategy linking advanced MXene-biochar adsorbents, wastewater remediation, nutrient recycling, biomass valorization, thermochemical energy recovery, and life-cycle sustainability assessment within the water-energy-resource nexus. The findings demonstrate the strong potential of MXene-biochar heterostructures for transforming wastewater-derived pollutants into value-added bioenergy and environmental resources, thereby supporting sustainable water management, renewable energy generation, and climate-change mitigation.