Adsorptive removal of Pb(II) from aqueous solution by novel PES/HMO ultrafiltration mixed matrix membrane

• Novel PES/HMO MMMs were fabricated for continuous adsorptive removal of toxic Pb(II).
• The maximum Pb(II) adsorption capacity of the optimized MMM was 204.1 mg/g.
• The kinetics of Pb(II) adsorption follows pseudo-second-order model.
• The membrane properties improved upon addition of HMO loading.
• The performance of MMM could be easily regenerated using acidic solution.

In this work, novel polyethersulfone (PES)/hydrous manganese dioxide (HMO) ultrafiltration (UF) mixed matrix membranes (MMMs) were prepared for adsorptive removal of Pb(II) by varying the weight ratio of HMO:PES in the membrane from 0 to 2.0. The membranes prepared were characterized with respect to chemistry, surface roughness and structural morphology using FTIR, AFM and SEM, respectively. The effects of HMO loadings on the membrane pure water flux, hydrophilicity, porosity and Pb(II) adsorption capacity were also studied. The results showed that although the membrane pore size tended to decrease with increasing HMO:PES weight ratio, the membrane water flux was not negatively affected. Instead the membrane water flux was increased with increasing HMO loadings which was attributable to the decreased contact angle value (more hydrophilic), increased porosity and greater surface roughness. Of all the membranes studied, it is found that the MMM prepared from the highest HMO:PES ratio demonstrated the highest Pb(II) uptake capacity (i.e. 204.1 mg/g) and this uptake capacity is comparable to most of the promising composite adsorbents reported in literature. Besides, the continuous UF experiments showed that the PES/HMO MMM can be potentially used for effective Pb(II) removal by producing permeate of high quality (<15 μg/L lead in water). By subjecting the Pb(II)-adsorbed MMM to a simple desorption process using HCl solution, it is reported that as high as 97.5% of the original adsorption capacity of membrane was able to be recovered, showing the reusability of the membrane for Pb(II) removal.