Construction of Al3+-carboxymethyl cellulose superhydrophilic layer on wood filter surface for highly efficient oil/water emulsion separation

Recently, there has been significant attention given to the development of oil-water emulsion separation filters made from renewable and inexpensive wood for the separation and purification of oily wastewater. However, the relatively large pore sizes of wood cross-section slices make it challenging to effectively separate emulsified oils (5–20 μm) in wastewater. We propose constructing a dense superhydrophilic layer of Al³⁺-carboxymethyl cellulose on the surface of a wood filter using a dip-coating process for separating oil/water emulsions. The Al³⁺-CMC layer exhibits stable surface superwettability with θ_oil > 160° under water, which repels the non-polar oil phase and selectively allows water to pass through. The wood filter optimized for emulsion separation can achieve an efficiency of 96.32 % and a filtration flux of 410 L m⁻² h⁻¹ bar⁻¹. It maintains stable recyclables even after 6 cycles. The Al³⁺-CMC@DW filter shows considerable potential for practical applications in oil/water emulsion separation.