Using alginate-based granular activated carbon hybridized with silica derived from sugarcane bagasse residues for adsorption of uremic toxins in dialysate

Abstract

In a wearable artificial kidney system, regeneration of spent dialysate solution, containing major uremic toxins such as creatinine and uric acid, is necessary for waste mitigation. In this study, hybrid granular activated carbons (GACs) of powdered activated carbon (AC) and mesoporous silica (MPS) derived from sugarcane bagasse (SCB) and SCB ash at various weight ratios were developed via gelation method using alginate as a bio-based polymer matrix. Notably, AC:MPS at 2:1 (w/w) was selected as a proper ratio in alginate-based hybrid GACs for adsorption kinetic and equilibrium isotherm studies due to their comparable swelling degree and adsorption efficiency of uremic toxins without granule deformation. Upon single and mixed uremic toxins at initial concentration of 100 ppm, the selected SCB-GAC exhibited similar adsorption capacities for creatinine (15–19 mg/g) and uric acid (29–36 mg/g). Maximum adsorption capacities at 43 mg/g for creatinine and 68 mg/g for uric acid were achieved in dialysate with mixed toxins at 500-ppm of each initial concentration, following the Sips adsorption isotherm behavior and the pseudo-second-order kinetic model. The selected SCB-GAC showed a declining adsorption efficiency for both uremic toxins from above 60 % to ~20 % over five cycles of regeneration using 5 % acetic acid.