Preparation of citric acid-modified cellulose materials with superwetting and antibacterial characteristics for highly-efficient separation of oil/water mixtures, emulsions, and dye-containing wastewater

Oil/water separation has become a pressing global challenge in the recent times due to the rapid increase in the development of industries, frequent oil spills, and chemical leakages. Therefore, it is in great demand to develop superwetting materials from bio-based and cheap substances for treating oil/water mixtures and emulsions. Herein, we prepared citric acid (CA)-modified cellulose materials (including cotton fabric and raw cotton) with superwetting properties through a green dip-coating approach. The as-prepared CA-modified cellulose materials showed superamphiphilicity in air and superoleophobicity underwater. The CA-modified cotton fabric (CMCF) can be utilized to treat oil/water mixtures and demonstrated remarkably high permeation fluxes (up to 107,900 L m⁻²h⁻¹) along with excellent separation efficiency (>99.99 %). The CA-modified raw cotton (CMRC) was applied for separating both surfactant-stabilized oil-in-water and surfactant-stabilized water-in-oil emulsions (SSOIWEs and SSWIOEs) exhibiting ultra-high permeation fluxes (up to 8,960 and 25,080 L m⁻²h⁻¹, respectively) under gravity. The separation efficiencies of SSOIWEs surpassed 99.18 % and the filtrates’ oil purity for SSWIOEs exceeded 99.98 %. In addition, the CMRC could be used to treat dye aqueous solutions and dye-containing emulsions. Moreover, CMRC also exhibited good antibacterial properties. Because of their excellent oil/water mixtures and emulsions separation abilities, green preparation process, and ease of mass production, our CA-modified cellulose materials have notable potential for practical applications.