Seeking high performance adsorbents for highly efficient treatment of wastewater containing organic dyes has become increasingly imperative worldwide. Herein, with a specific surface area (SSA) of 2,745.4 m²·g⁻¹, trace N-doped porous biochar nanospheres (NPBs) are derived for the first time from affluent waste corn roots, via a hydrothermal conversion followed by a mild calcined activation by K₂CO₃ (KC) in the presence of low virulent melamine. Melamine acts as N source and synergistic activator for significant promotion in SSA, pore volume, and surface defects. The obtained NPBs (CHC-0.5N-4KC-900) are confirmed as superior adsorbents for removal of organic dyes rhodamine B (RhB, q_m = 1,630.7 mg·g⁻¹) and Congo red (CR, q_m = 1,766.2 mg·g⁻¹) as well as their mixtures, within not only a low (< 50 mg·L⁻¹) but also a high (> 50, esp. 250–1500 mg·L⁻¹) concentration range. The values for q_m are far beyond commercially activated carbon (AC) as well as most reported biomass derived carbons, undoubtedly revealing the NPBs as great promising candidate adsorbents for disposal of real industrial wastewater. In addition, the adsorption of RhB is fitted by Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models. The kinetic analysis indicates that the adsorption before equilibrium conforms to the pseudo-second-order model, and the hydrogen bonding, electrostatic attraction, and esp. π–π interaction have contributed to the superior adsorption performance of the NPBs.

Towards bottlenecks demonstrated by typical Fenton-like catalysts in advanced oxidation processes (AOPs) for wastewater treatment, novel hierarchical porous ${\text{Mn}}^{\text{2+}}{\text{Mn}}_{\text{6}}^{\text{3+}}{\text{SiO}}_{\text{12}}$ (Mn₇SiO₁₂, MSO-12) microspheres (specific surface area: 434.90 m²·g⁻¹, pore volume: 0.78 cm³·g⁻¹) were rationally designed and achieved via a simple one-pot hydrothermal method (150 °C and 12.0 h) without any pre-prepared templates or organic solvents, by using abundant MnCl₂·4H₂O and Na₂SiO₃·9H₂O as the basic raw materials. The MSO-12 microspheres are confirmed as high-efficiency Fenton-like catalysts for degradation of organic dyes (methylene blue (MeB), Rhodamine B (RhB), and methyl blue (MB)) in the presence of H₂O₂, with impressively high specific consumption amount of MeB (R = 12.35 mg·g⁻¹·min⁻¹) and extremely low leaching of Mn (Mn_loss% = 0.27%). Simultaneously, the synergetic effect of adsorption and degradation on the superior removal of MeB is uncovered. The excellent recycling performances, especially the satisfactory removal of MeB from the actual water bodies (e.g., tap water and river water), as well as potential applications for degradation of RhB and MB enable the MSO-12 microspheres as a novel promising competitive candidate Fenton-like catalyst.