Coffee grounds-derived core-shell aerogels: Preparation and application for diesel pollutant degradation in water

The effective and environmentally friendly management of oily wastewater, alongside the beneficial conversion of waste biomass, holds paramount importance for environmental conservation, public health, and sustainable societal progress. In this research, an innovative biomass core-shell bioreactor (CGC@SiO₂ aerogel) with selective adsorption and degradation properties was developed. The reactor's core is composed of coffee cellulose aerogel, offering a porous framework conducive to microbial colonization while safeguarding microorganisms from adverse external factors. The shell integrates hydrophobic silica enriched with polydimethylsiloxane, which alters the material's hydrophilic properties, enabling it to remain afloat on water for up to 100 days. This superhydrophobic layer maintained a contact angle of 150° even after ten consecutive rubbings. Experimental results indicate that the material performs exceptionally well in oil-water separation, as demonstrated by its success in 9 consecutive oil-water separations. It achieved 99 % selective adsorption, 91 % removal, and 46.2 % degradation of a 3 wt.% diesel solution under conditions of 37 °C, 120 r/min, and pH = 7. Additionally, tests assessing environmental tolerance revealed the material's robust adaptability and stability across varying pH levels and temperatures. Compared to traditional hydrophobic and lipophilic materials or free-floating microorganisms, CGC@SiO₂ aerogel not only efficiently captures oil pollutants but also degrades them into non-hazardous substances. Combining biodegradation with selective adsorption has shown to be an effective approach for treating oily wastewater, offering significant practical application potential. The low-carbon production of CGC@SiO₂ aerogel aligns with circular economy principles, underscoring its role in sustainable development.