Hybrid multi-walled carbon nanotubes-alginate-polysulfone beads for adsorption of bisphenol-A from aqueous solution

In recent years, the potential application of carbon nanotubes (CNTs) as sorbent materials in wastewater treatment has garnered tremendous attention. Concerns that CNTs may be toxic to living organism, however, necessitate that the containment of CNTs to prevent their release into the environment in order to realize their practical application in wastewater treatment. In this study, we immobilized multi-walled carbon nanotubes (MWCNTs) within macro-calcium alginate beads. The composite beads were coated with an additional polysulfone (Psf) layer both to provide an external barrier to MWCNTs release into the effluent and also to improve the mechanical integrity of the beads. The hybrid beads were tested for their capacity to remove the bio-refractory endocrine disruptor compound bisphenol-A (BPA) using batch and packed bead column experiments. Maximum BPA removal was achieved at 22% MWCNTs, which was the dispersion limit of MWCNTs in our study. The adsorption of BPA followed Langmuir isotherm model with good correlation. The maximum adsorption capacity of the composite beads of dosage 4 g L⁻¹ as obtained using the Langmuir model was 24.69 mg g⁻¹. Addition of the Psf layer, together with MWCNTs, improved the bead compression performance by up to twelvefold at 40% compressive extension. This study showed that the hybrid alginate-Psf bead may serve as compartment for encapsulation of MWCNTs for removal of BPA. Improved compression performance introduced by addition of Psf layer could protect hybrid beads used, for example, in reactors subjected to extreme conditions such as high flow rates.