净化 (jìnghuà) means to purify in a broad sense — air, water, environment, or the mind/spirit. 清洗 (qīngxǐ) specifically means to clean with water or liquid, or to purge undesirable elements (e.g., a team); 纯洁 (chúnjié) as a verb (less common) focuses on moral/spiritual purity rather than physical or environmental cleanup. 提炼 (tíliàn) is for extracting and refining substances like ore or oil, not general purification.