Robust and durable polymer grafted cotton fabrics for sequential oil/water separation and heavy metal ions removal based on surface initiated ATRP

Abstract

Both oil spill and heavy metal ions in the industrial wastewater cause severe problems for aquatic ecosystem and human health. Herein, a preparation method of solid particle-free polymer grafted biodegradable cotton fabrics without auxiliary of fluorine and silicon was proposed for sequential separation of oil/water mixture and removal of heavy metal ions. Superhydrophobic poly (acrylonitrile-co-styrene) grafted cotton fabrics (CF-g-PSAN) designed for oil/water separation were fabricated by successive initiator tethering and polymer grafting via surface-initiated atom transfer radical polymerization (SI-ATRP). Furthermore, pendant amino diethylenepentamine groups were introduced to surface grafted brushes of aminated CF-g-PSAN (CF-g-APSAN) by reaction with tetraethylenepentamine. The obtained CF-g-PSAN exhibited superhydrophobicity with WCA achieving 150° due to the combination of surface tethered hydrophobic PSAN and increased surface roughness. High grafting density of hydrophilic CF-g-APSAN enabled heavy metal ions free access towards APSAN brushes in aqueous medium and maximized the number of accessible chelating sites towards heavy metal ions originating from the high affinity of pendent amino diethylenepentamine groups. In the sequential treatments of oil/water separation and heavy metal ion removal, the polymer grafted cotton fabrics achieved a high oil/water separation efficiency exceeding 97.8% and demonstrated as excellent adsorbent towards heavy metal ions with record-high uptake capacity of about 682.5, 375.8, 438.3, 535.7 mg/g for Pb (II), Cu (II), Zn (II), and Ni (II), respectively. Furthermore, the excellent efficiency, operability, and recyclability of CF-g-APSAN were verified in dealing with aqueous solution of the separated water phase under dynamic flow conditions with high removal rates of 91, 89, 89, and 87% for Pb (II), Cu (II), Zn (II), and Ni (II). The recyclable CF-g-PSAN and CF-g-APSAN demonstrated combined high separation efficiency and record-high adsorption capacity, which are expected to find industrial applications in oily wastewater treatment as sustainable and highly effective materials.