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

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 (q(max)) of 95.2 and 91.7 mg/g were obtained for Cd2+ and Zn2+ ions, respectively. Results established that all isotherm models attained R-2 more than 0.9, where the Langmuir isotherm achieved the highest one with R-2 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.

Automated summary

New composite adsorptive membranes were developed from non-living marine algae and cellulose acetate to remove cadmium and zinc ions from aqueous media with high efficiency. The membranes showed a significant increase in porosity and demonstrated a strong affinity for the target ions. The study also highlighted the suitability of the system for heavy metal removal through the application of 3R processes.