Tunable polypyrrole-coated cellulose aerogel via in situ polymerization for high-performance solar-powered water purification: Effects of porosity, photothermal conversion, and long-term stability

The direct utilization of solar energy to convert contaminated water into clean, potable water presents a sustainable and eco–friendly solution to global water scarcity. However, this process is often limited by low evaporation rates and the use of expensive photothermal materials. In this study, we address these challenges by developing a novel polypyrrole (PPy)–coated cellulose aerogel (WP@PPy) using waste paper (WP) as a low–cost, cellulose–rich precursor. The engineered aerogel exhibits tunable porosity, low density, mechanical flexibility, and strong hydrophilicity, with a PPy coating that significantly enhances light absorption and photothermal conversion. Under standard conditions (2 × 2 aerogel, 50 mL tap water, room temperature, 60 min, and 1 sun illumination), WP@PPy aerogel achieves a high solar–driven evaporation rate with an energy conversion efficiency of 91.53 %, compared to only 47.83 % for uncoated WP aerogel. Moreover, WP@PPy aerogel demonstrates excellent long–term durability, sustaining performance over 28 h of operation across 7 days. Importantly, it effectively removes a wide range of contaminants including dye, heavy metals, oil–water mixture, saline water, and real seawater, highlighting its potential for practical wastewater treatment and desalination. This work provides a promising route for environmentally friendly, multifunctional water purification using readily available materials.