Preparation And AOP Properties Of Biochar/Cobalt-based Composite Catalytic Materials

Transformation of difficult-to-degrade organic matter into pollution-free substances still remains highly desired but persistent challenges towards cost-effective and sustainable strategy.Advanced oxidation processes（AOPs）can produce highly reactive and adaptable sulfate(SO₄^·-)and hydroxyl（^·OH）radicals through the activation of peroxymonosulfate（PMS）by heterogeneous catalysts,thereby degrading organic pollutants（such as organic dyes,phenolic compounds,and antibiotic compounds）in situ to carbon dioxide and water.In general,the cobalt-PMS coupling reaction is one of the most effective methods for preparing reactive radicals.Taking the principle of“sustainable development and environmental protection”as the starting point,the quest for novel material with simple preparation method,cycle-to-cycle stability and durable continuous operation capability is an urgent need to remediate efficiently the actual organic wastewater.Herein,nitrogen-doped bio-carbon/cobalt-based composite catalytic materials were designed and prepared with different production processes using biomass-derived sodium alginate as a carrier,aiming to explore their structure-activity relationship,activation mechanism,and application potential.1)In the first part,seaweed-derived N-doped versatile carbonaceous beads with Co_xO_y（Co-NC-0.25-700°C）were employed as novel catalysts to activate PMS for degradation of multiple organic pollutants.Profiting from the improved structure-activity relationship and the synergistic effect between C-N skeleton and Co_xO_ynanoparticles,Co-NC-0.25-700°C exhibited excellent degradation performance for various common organic pollutants.The universal applicability of Co-NC-0.25-700°C was demonstrated by degrading other types of organic pollutants in various systems.For this type of newly fabricated high-performance versatile composites,the relationship of structure-property is plausibly proposed.Of particular interest is that,during the preparation process,the co-complexation between Co²⁺and sodium alginate/polyethyleneimine would lead to enhanced self-assembly and dispersion of Co²⁺at the molecular level,which not only furnish nucleation sites for in-situ growth of the Co_xO_ynanoparticles but also control their aggregation during carbonization.The unique“egg-box”and 3D interconnected polymer network structure synergistically control the leaching of Co_xO_ynanoparticles.The coupling of wonderful magnetic properties and bead-like shape endows the resultant composites with remarkable reusability and recyclability.More far-reaching,the simulation of actual water conditions and the design of continuous-flow reactors have taken a huge step towards the batch treatment of organic pollutants in the real process.2)In the second part,for this type of new concept of“utilizing waste treating waste”,a“circular recycling”process for heavy metal and organic contaminants-modeled solutions remediation was demonstrated;that is,for the first time,it circularly utilizes the Co²⁺adsorbed composites and transforms it to Co/N-doped carbonaceous catalyst through carbonization to efficiently degrade organic pollutants.A precondition,for the circular utilization of Co²⁺adsorbed composites in a sustainable system,is satisfactory Co²⁺adsorption capacity.Given the co-modification of alginate precursor via melamine/polyethyleneimine,the adsorbent（Ca-Me/SA@0.75PEI;N content=15.68%）with increased surface chelating sites and polarity exhibited strong affinity toward Co²⁺（698.62 mg/g）.Subsequently,to further utilize and improve the cyclic stability of Co²⁺adsorbed composites in PMS activation for organic pollutant degradation,it was facilely transformed into Co/N-doped carbonaceous catalyst by controllable carbonization.The framework confinement effect of the unique watermelon-like structure effectively immobilizes active sites,thereby improving the stability of adsorptive catalyst.Indeed,this novel supporting materials with bead-like shape can enhance the mechanical properties,effectively solving the problem of powder materials being difficult to apply in large-scale column operation（adsorption/degradation）experiments.More significantly,detailed column operation experiments revealed the long-term operational stability of as-prepared materials in continuous wastewater treatment.In the end,the economic calculation verified the possibility of circular economy,namely,utilizing adsorbed metal ions as raw materials to treat industrial organic wastewater.