Highly efficient adsorptive membrane for heavy metal removal based on Ulva fasciata biomass

Abstract

New composite adsorptive membranes were prepared from non-living Ulva fasciata (U), marine algae and cellulose acetate (CA) as polymer matrix to develop CA–U composite membranes with different ratios using the phase inversion technique. These CA–U membranes were used for cadmium (Cd2+) and zinc (Zn2+) ion removal from aqueous media. The prepared membranes were characterized via different instrumental techniques as ATR-FTIR, SEM and EDX in addition to swelling and porosity measurements. Afterwards, they were optimized for Cd2+ and Zn2+ removal through one factor at a time (OFAT) trials followed by full factorial design. The morphology and porosity measurements were highly affected by the addition of Ulva fasciata biosorbent and showed a large increase of the size and density of pores of the CA–U membrane. Maximum adsorption capacities (qmax) of 95.2 and 91.7 mg/g were obtained for Cd2+ and Zn2+ ions, respectively. Results established that all isotherm models attained R2 more than 0.9, where the Langmuir isotherm achieved the highest one with R2 0.9993 for Cd2+ and 0.9965 for Zn2+, and the adsorption process belongs to the pseudo-1st-order kinetic model. The CA–U membrane displayed a higher affinity for Cd2+ and Zn2+ ion removal by three to four times than the blank CA membrane. Furthermore, 3R processes (removal, recovery and re-use) were applied and indicated the suitability of this system in heavy metal removal with high efficiency.