The preparation of starch-based green adsorption gel with tunable water channels through extrusion-dual cross-linking method.

In addressing the challenges of recovery and microparticle residue associated with biochar, loading biochar with starch presents a viable solution. However, starch's high hydrophilicity and viscosity introduce water resistance and uniform loading issues. This study proposes an innovative ionically synergistic dual crosslinking modification method, utilizing an extruder barrel as a novel reactor. This method enables the construction of highly water-resistant starch gels and the uniform and robust loading of biochar micro-nanoparticles within the gel matrix, achieving the "one-step" preparation of starch-biochar-based adsorptive gels. The starch-biochar-based adsorptive gel (Bc-S-D) exhibits excellent removal efficiency for the hazardous waste methylene blue (MB) with a qe value of 549.45 mg/g. This removal efficiency is maintained at 85.37 ± 0.08 % even after five cycles. The textural results indicate that Bc-S-D maintains a high recovery performance of 91.51 % after prolonged water immersion. Scanning Electron Microscopy (SEM) reveals that it has the lowest porosity (47 ± 3.36 %) and micropore size (16.53 ± 2.71 μm). Furthermore, the specific surface area was determined using the Brunauer-Emmett-Teller (BET) model, which is 7.46 ± 0.03 m2/g, representing a 448.53 % increase compared to the unmodified state. A quasi-primary kinetic model for the adsorption of MB on the adsorbent follows the Langmuir model. The starch-biochar-based adsorption gel is also appropriate for high-temperature dyeing wastewater adsorption situations because of its superior water resistance, structural recoverability, and high-temperature stability, which allow rapid, residue-free separation and recovery. This research provides a new reaction method for preparing modification biological macromolecules and loading new biological macromolecule functional materials to achieve the full-cycle green treatment of dyeing wastewater.