Aiming at the problems of the large storage, complex composition, low comprehensive utilization rate, and high environmental impact of coal gangue, this paper carried out experimental research on the preparation of iron oxide red from high-iron gangue by calcination activation, acid leaching, extraction, and the hydrothermal synthesis of coal gangue. The experimental results show that when the calcination temperature of coal gangue is 500 °C, the calcination time is 1.5 h, the optimal concentration of iron removal is 6 mol/L, the acid leaching temperature is 80 °C, the acid leaching time is 1 h, and the liquid——solid mass ratio is 4:1; the iron dissolution rate can reach 87.64%. A solvent extraction method (TBP-SK–hydrochloric acid system) was used to extract the leachate, and a solution with iron content up to 99.21% was obtained. By controlling the optimum hydrothermal conditions (pH = 9, temperature 170 °C, reaction time 5 h), high-purity iron oxide red product can be prepared; the yield is 80.07%. The red iron oxide was characterized by XRD, SEM-EDS, particle-size analysis, and ICP-OES. The results show that the red iron oxide peak has a cubic microstructure, an average particle size of 167.16 μm, and a purity of 99.16%. The quality of the prepared iron oxide red product meets the requirement of 98.5% of the “YHT4 Iron oxide Standard for ferrite”. It can be used as a raw material to produce high-performance soft magnetic ferrite. In summary, this experimental study on the preparation of iron oxide red from coal gangue is of great significance for the comprehensive utilization of coal gangue to realize the sustainable development of the environment and economy.

Catalytic pyrolysis has emerged as a promising approach for converting waste plastics into high-value-added chemicals and fuels. This study aims to investigate the effect of calcination temperature on the catalytic performance of FeCoO_x/Al₂O₃ catalysts for high-density polyethylene (HDPE) pyrolysis and to optimize the catalyst preparation conditions for maximizing valuable product yields. FeCoO_x/Al₂O₃ catalysts were synthesized via a hydrothermal method and calcined at various temperatures (300–700 °C). The results demonstrate that calcination temperature significantly influences product distribution: gas yield increased with rising calcination temperature, whereas carbon yield, hydrogen yield, and hydrogen content decreased accordingly. Among all tested temperatures, the catalyst calcined at 500 °C achieved the optimal performance, yielding solid carbon at 23.0 wt. % with a hydrogen content of 80 vol.%. This superior performance can be attributed to its larger specific surface area, a richer pore structure, and better reducibility compared to those calcined at higher temperatures, which also facilitated the formation of solid carbon with the highest degree of graphitization and purity. This work provides technical guidance for the high-value utilization of waste plastics through catalytic pyrolysis.

Synergistic catalysis by iron and acidic sites on acid-modified coal gangue promotes PP dehydrocracking, boosting gas yield and liquid quality.