Novel bio-adsorbent of alginate/HTC hydrochar & alginate/HTH hydrochar composite beads for removal of basic blue 9 from water

Adsorbents developed within the framework of circular engineering, which aim to foster a sustainable economy and environment, can serve as strong alternatives to traditional adsorbents. This research involved the modification of carrot pomace biomass through hydrothermal carbonization (HTC) and hydrothermal humification (HTH) processes, resulting in the creation of beads using sodium alginate biopolymer (HTC/Alg and HTH/Alg beads) that effectively adsorb Basic Blue 9 (BB9) dye. To the best of our knowledge, this is the first study to incorporate hydrochar into alginate-based composite beads, using pomace carrot as a novel and sustainable biomass precursor. The structural and morphological characteristics of both types of adsorbents were analyzed using techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), zeta potential measurements, and Brunauer-Emmett-Teller (BET) surface area analysis. The performance of the adsorbents was evaluated based on variables including pH, dosage of adsorbent, dye concentration, and duration of adsorption. The maximum adsorption capacities were determined to be 575.845 mg/g for HTH/Alg beads and 580.193 mg/g for HTC/Alg beads, with the Redlich-Peterson isotherm being the most suitable model to describe the adsorption behavior of the beads. Furthermore, the adsorption kinetics for both adsorbents conformed to the Elovich model. Isotherm and kinetic modeling indicate that electrostatic interactions and chemisorption are the dominant mechanisms driving dye removal. .