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In this paper, a unique hydrolysis reaction process for the production of 4‐Aminoantipyrine (AA) is investigated. A liquid‐phase analytical method for AA is established, and the amount of sulfuric acid, reaction temperature, reaction time are studied. On the basis of single factor experiments, the response surface method (RSM) is used to systematically optimize the conditions of the hydrolysis reaction. The optimum conditions are n(AT‐SO4): n(H2SO4)=0.73, the reaction temperature is 98 °C, the reaction time is 91 min, and the AA yield reaches 90.80 %. Compared with the previous process, the yield of AA is improved and colloids are significantly reduced. Under optimum process conditions, a kinetic model is constructed in the range of 358 K–373 K, which activation energy, Ea=33.21 kJ/mol, and the pre‐exponential factor, A=1586.84. In addition, the product AA is characterized by IR analysis, LC‐MS analysis, GC‐MS analysis and hydrolysis reaction mechanism are investigated. [ABSTRACT FROM AUTHOR]

Herein we synthesized biochar/iron oxide composite (C/α‐Fe2O3/γ‐Fe2O3) by two‐step calcination method. The prepared C/α‐Fe2O3/γ‐Fe2O3 had a highly pure and a concentration ratio of α‐Fe2O3 and γ‐Fe2O3 about 1 : 1. The optical properties of as‐synthesized C/α‐Fe2O3/γ‐Fe2O3 show a lower bandgap energy (1.90 eV) than that of pure C/α‐Fe2O3 (2.02 eV). The effects of different biochar composite catalysts on the removal of amino black were investigated. Upon illumination, the total removal rate of amino black dye by C/α‐Fe2O3/γ‐Fe2O3 catalyst reached 98 %, which was about 1.7 times that of C/α‐Fe2O3. In addition, the coercivity and the remanence intensity of C/α‐Fe2O3/γ‐Fe2O3 is respectively 1.81 times and 7.17 times that of C/α‐Fe2O3. The catalyst could be magnetically separated and reused for five times with a slight loss of its reactivity. The study of biochar composite provides a new direction for the removal of toxic organic dye in wastewater. [ABSTRACT FROM AUTHOR]