In this study, an effective circulating system was developed to remove heavy metals in medical waste incineration (MWI) fly ash. MWI fly ash (MWIFA)-column experiments were performed to remove Cu, Pb, Zn, Cd and Ni from MWIFA using EDTA disodium (Na₂EDTA). Iron-column experiments were conducted to study the removal effect of zero-valent iron on the five heavy metals from washing wastewater. TCLP test method was employed to evaluate heavy metals toxicity of MWIFA residues generated after 0-0.2 mol/L Na₂EDTA solution treated. After washed by 0.2 mol/L Na₂EDTA solution, TCLP leaching values of Cu, Pb, Zn, Cd and Ni were the lowest and satisfied the standard (GB 5085.3–2007), and the leaching values were 58.4±2.0 mg/L, 2.81±0.14 mg/L, 64.3±4.0 mg/L, 0.156±0.005 mg/L, 0.381±0.006 mg/L. Concentrations of Cu, Pb, Zn, Cd and Ni in iron-column effluent were reduced by 99.7%, 91.6%, 91.6%, 75.4% and 75.7%, respectively. Na₂EDTA was recovered and recycled to the removal of heavy metals from MWIFA. Compared new Na₂EDTA solution with recycled Na₂EDTA solution, recycled Na₂EDTA and water could be reutilized to dispose MWIFA. The removal efficiencies of Cu, Pb, Zn, Cd and Ni by recycled 0.2 mol/L Na₂EDTA solution were 67.1%, 68.8%, 63.2%, 73.9%, 50.7%, respectively, the removal efficiencies that using recovered Na₂EDTA decreased by 2.6%, 3.9%, 3.3%, 4.2%, and 1.6%, respectively. Successive batch experiments were also conducted to evaluate industrialization potential and reusable times for recycled Na₂EDTA. After 4 recirculation cycles, extraction efficiencies of Pb and Cd (removal efficiency at different cycles divided by removal efficiency of new Na₂EDTA) declined towards 80%.

In this study, Ni nanoparticles supported on renewable porous carbon were prepared using hydrochar as a carbon precursor via in situ formation and self-reduction. The structure properties of the prepared nanocatalysts were characterized by multiple techniques, including XRD, SEM, and HR-TEM, and the dry reforming of methane (DRM) performance of the nanocatalysts in terms of conversion efficiency and reactivity stability was evaluated. The results revealed that the Ni²⁺ was uniformly anchored on the surface of the hydrochar, and subsequently the Ni nanoparticles were well dispersed in the composite with a diameter of less than 8 nm and had a narrow particle size distribution at a temperature lower than 800 °C. With an increased temperature from 800 to 900 °C, the significant sintering and agglomeration of nickel particles and the transformation from amorphous carbon to graphitic structure were observed in the composite. The nanocatalysts prepared at a temperature of 700 °C (Ni@C-700) and 800 °C (Ni@C-800) exhibited a high reforming conversion rate and catalytic stability of CH₄ by CO₂ (around 52% for Ni@C-700 and 70% for Ni@C-800 after 800 min of run-time, respectively). As for the composite obtained at 900 (Ni@C-900), the highly graphitic degree was coupled with the significantly increased nickel particle size, and this resulted in a remarkably decreased conversion efficiency. The present study offers a valuable application of the hydrochar and a facile and green approach to prepare highly active and cost-efficient Ni nanoparticles on porous carbons towards the dry reforming of methane.

In this study, the significant iron-based material, hydroxyl-functionalized ball-milled zero-valent iron/Fe₃O₄ (HFB-ZVI/Fe₃O₄) was employed for the experiments. The performance of the Electro + HFB-ZVI/Fe₃O₄+ Oxone system for the degradation of chemical oxygen demand (COD) in antibiotic wastewater was investigated. A direct current was applied between a graphite plate anode and two iron plate cathodes, a series of operational parameters, such as applied electric current, dosage of HFB-ZVI/Fe₃O₄ composite, dosage of Oxone, and initial solution pH, were explored to evaluate the oxidation process. Application of electric current enhanced the gradual degradation of COD, and the increase of current intensity accelerated COD degradation. Neutral condition was favorable for the rapid degradation of COD in short reaction time via Electro + HFB-ZVI/Fe₃O₄+ Oxone process and promoted the degradation efficiency of COD. Increase of electric current gradually decreased reaction solution pH, the larger the electric current applied in the reaction process, the lower the final pH of the reaction solution. Under the optimal experimental conditions (1 g/L HFB-ZVI/Fe₃O₄ composite, 0.3 g/L Oxone, current intensity =500 mA, initial solution pH = 7.85), Electro + HFB-ZVI/Fe₃O₄+ Oxone achieved 99% COD degradation in antibiotic wastewater. Radicals quenching experiments indicated the contribution to COD degradation by hydroxyl radicals (HO^•), sulfate radicals (SO₄^•-) and other oxidant were 66.03%, 24.014% and 9.756%, respectively. Possible mechanism of COD degradation in Electro + HFB-ZVI/Fe₃O₄+ Oxone system was also discussed in this study. The findings in this work provided useful information for the treatment of wastewater. GRAPHICAL ABSTRACT