In-Situ Production of Cellulose Nanocrystal-Alginate Hydrogel Beads and Dye Removal in Fixed Bed Adsorption Column

This work presentsa process unit incorporating sustainableadsorbents that demonstrates promising application in wastewater treatment. Inthis study, adsorption modeling of a model organic dye, methyleneblue (MB), onto cellulose nanocrystal-alginate (CNC-ALG) hydrogelbeads in a fixed bed column until full breakthrough was performed.A method for the in-situ production and loading of CNC-ALG hydrogelbeads in a fixed bed column adsorption process was proposed for thefirst time. Fixed bed column adsorption experiments using MB and 0.5wt % ALG and 2 wt % CNC beads were conducted using various initialdye concentrations, influent flow rates and adsorbent mass. The resultswere evaluated using a mathematical model with axial dispersion, filmand pore diffusion to predict the fluid and particle phase continuity,and good agreement with the experimental data was observed. Experimentsconducted using the spent hydrogel beads in a fixed bed column suggestedthat these adsorbents could be regenerated to 81% of its originaladsorption capacity upon elution with 1 M hydrochloric acid:ethanol(1:1 v:v), and a subsequent adsorption cycle indicated that theseadsorbents could achieve 96% of the renewed adsorption capacity. Furthermore,both batch and fixed bed column adsorption experiments displayed themaximum adsorption capacities of 401.8 and 410.5 mg MB/g adsorbent,respectively, and these similar values signify the reproducibilityof the adsorption capacity of the adsorbents when operated under batchand continuous modes.

Automated summary

This study introduces a process unit using sustainable adsorbents for wastewater treatment with promising results. It proposes a method for in-situ production and loading of cellulose nanocrystal-alginate (CNC-ALG) hydrogel beads in a fixed bed column for adsorption processes. The experiments and mathematical modelling demonstrate the effectiveness and regenerability of the adsorbents, with similar maximum adsorption capacities observed in both batch and continuous modes of operation.