Surface-engineered naturally-derived xerogel for boosting chelation of refractory contaminants: From low-temperature hydrochar strategies, characterization probes to underlying mechanisms​

Conventional filtration results in secondary pollution due to poor degradability and disposal challenges. We established a protocol for synthesizing a metal-free Xerogel Infiltration Matrix (XIM) from banana via low-temperature HTC reactions via soft control of carbon-rich hydrochar. To address sustainability gaps, main signature of synthesis was the use of natural precursors and solvents unlike chemically driven high temperatures routes. XIM dominated by turbostratic configuration and intense C1s and O1s XPS signals pointed oxygenated organic hybrid surfaces. Structurally, matrix contained a condensed carbonaceous core with a moderate fraction of thermally labile species facilitating relaxation, secondary crystallization, and reactive transitions. Raman primary peaks identified D (disorder-induced) and G band (graphitic configuration), while carbon-iodine showed additional features that were absent in pristine or carbon-chromium spectral signatures. XIM deployment circumvented prerequisites of inert environments, decarbonated water, or pH regulations. Chelation was rate-regulated by chemisorption and intraparticle diffusion, while energetics confirmed spontaneous, endothermic, and entropy-driven process across moderate to high temperatures. Contaminant chelating models demonstrated that surface engineering could achieve significant sequestration. In comparison to widely used commercial activated carbon, XIM demonstrated superior functional performance in the treatment of contaminated waters containing carcinogenic chromium and in capture g iodine from amphiphilic (polar and non-polar) environments. Xerogel maintained efficacy across ionic strengths, pH levels, and co-occurring metal interferences. Synergistic enhancement observed with Fe3+; conversely, inhibition variability detected in presence of Cu2+, Pb2+, Ag+ and As5+. Xerogel exhibited stability, supported by leaching test and aging deployments. Information provided will improve underlying local mechanisms on naturally-derived xerogel that optimizes both separation effectiveness and degradability.