Hydrogel-activated hydrochar synergy for efficient wastewater purification: tackling imidacloprid pesticides and crystal violet dye

Abstract

With the growing global water crisis, wastewater reuse is increasingly essential, particularly in applications where treated water is safe for reuse. This study presents a sustainable hydrogel adsorbent, CMC-g-poly(AA-co-AM)/AHC, synthesized from carboxymethyl cellulose (CMC), activated hydrochar (AHC), acrylic acid (AA), and acrylamide (AM), for the removal of crystal violet (CV) dye and imidacloprid (Imida) pesticide. The microwave-assisted synthesis of AHC nanoparticles from bagasse offers dual benefits: reducing waste via agricultural byproduct valorization and enabling cost-effective water purification. The study evaluates the hydrogel’s chemical, physical, thermal, and rheological properties, as well as its adsorption efficiency under varying conditions, including pH, sorbent dose, salinity, ionic interference, temperature and contact time, supported by kinetic and isotherm modeling. The H10 hydrogel, incorporating 10.0% AHC, exhibited superior physical and rheological properties, achieving 94.0% removal efficiency for CV and 81.0% for Imida, with Langmuir-modeled maximum adsorption capacities of 312.5 mg/g for CV and 270 mg/g for Imida. Sorption–desorption experiments revealed enhanced reusability, with CV efficiency increasing from 93.8 to 97% and Imida from 88.0 to 91.6% after regeneration. Temperature effects demonstrated improved adsorption rates at higher temperatures (25 °C–40 °C), while ionic interference significantly impacted Imida adsorption. These findings reinforce the hydrogel’s potential for sustainable wastewater treatment, highlighting its reusability, efficiency, and adaptability for real-world applications.