Tuning hydrophobicity and microporosity of NaY zeolite for greatly enhanced adsorption of alcohols and acids from Fischer-Tropsch wastewater

Adsorption and recovery of valuable alcohols and acids from industrial wastewater are of significant importance for sustainable chemical production and environmental remediation. Developing high-capacity adsorbents requires understanding the effects of micropore structure and surface hydrophilicity/hydrophobicity on adsorption performance. NaY zeolite with a well-defined pore structure was modified using methyltriethoxysilane (MTES) as adsorbents with varying hydrophobicities and evaluated by alcohols/acids and FTS wastewater measurements. MTES modification preserved the crystal structure of NaY zeolite; the hydrophobicity of zeolites increased, while the specific surface area and micropore volume decreased with increasing MTES dosage. Upon adsorption measurements, zeolites with higher hydrophilicity exhibited lower alcohol/acid adsorption capacity; whereas a moderate hydrophobicity (contact angle of 84°) and relatively high micropore volume (0.19 cm 3 /g) achieved the highest adsorption capacity of 328 mg/g, outperforming the zeolite with higher hydrophobicity and lower micropore content. Adsorption isotherm fitting revealed that alcohol/acid adsorption on the zeolites followed the Langmuir model. This work provides a strategic guideline for designing efficient zeolite-based adsorbents by balancing hydrophobicity and porosity. Future studies should uncover the adsorption mechanism at the hydrophobic interface for further improving the long-term stability of the modified zeolites.