Effective activated nutrient components of coal gangue with thermal modification and its passivation of lead ions

• An effective agent of CaCl2 was used to modify coal gangue with active roasting. • Nutrient release in modified coal gangue and its passivation of Pb2+ was obtained. • The effect of roasting agents on nutrient release and Pb2+ removal was investigated. • The release mechanism of nutrients (available Si, K, P) in coal gangue was analyzed. • The fixation and adsorption mechanism of Pb2+ by modified coal gangue was evaluated. Coal gangue is used as raw material to enhance its nutritional component activity and adsorption performance for lead ions (Pb²⁺) through thermal modification, which may be applied in the remediation of polluted soil. The effects of different modification conditions on the content of available silicon, phosphorus, and potassium in coal gangue and the removal rate of Pb 2+ in a solution system were investigated. The adsorption mechanism of Pb 2+ by thermally modified coal gangue was analyzed by using XRD, XPS, SEM-EDS, and other characterization methods. The results show that under suitable modification conditions, the contents of available silicon, potassium and phosphorus in modified coal gangue roasted at 600 °C (Ca-CG-600) were 10,375 mg/kg, 268 mg/kg and 6.1 mg/kg, respectively, whereas those in raw coal gangue were 388 mg/kg, 169 mg/kg and 2.6 mg/kg, respectively. The release of available nutrient elements was promoted due to the destruction of kaolinite (Al 2 [Si 2 O 5 ](OH) 4 ), muscovite (KAl 2 [AlSi 3 O 10 ](OH) 2 ) and monetite (Ca(H 2 PO 4 )H 2 O) in the coal gangue. The pore structure of activated coal gangue was increased, which facilitated the adsorption of Pb 2+ . The removal rate of Pb 2+ reached 99.6 % under the optimal adsorption conditions with Ca-CG-600. The adsorption of Pb 2+ by Ca-CG-600 mainly occurred via ion exchange with Ca 2+ and Na + in NaCaAlSi 3 O 8 (OH), forming Pb 6.34 Al 12.7 Si 11.3 O 48 . Additionally, precipitates such as Pb 2 [CO 3 ]Cl 2 and PbSO 4 formed through the combination of Pb 2+ with CO 3 2- and SO 4 2- . This study may provide new insights into the comprehensive utilization of coal gangue and efficient removal of Pb 2+ . Nutrient release in modified coal gangue with roasting and its passivation of Pb 2+