Research on whitening modification of green mud and its application

Abstract This study employs a carbonation coating whitening modification method, supplemented by ultrasonic treatment, to form a calcium carbonate coating layer on the surface of green mud particles, thereby enhancing their whiteness performance. Using the optical properties of composite particles as evaluation indicators, the reaction conditions of the ultrasonic carbonation green mud system were explored. By combining single-factor experiments and orthogonal experiments, the optimal reaction conditions for ultrasonic-assisted coating whitening of green mud were determined. Under ultrasonic action, key issues such as poor surface structure of green mud particles, particle agglomeration in the whitening modification system, non-dominant heterogeneous nucleation, and poor mass transfer effects can be addressed. After ultrasonic treatment, the whiteness of green mud increased from 33.27 % to 68.32 %. When the composite particles were used as fillers in containerboard, compared to the original green mud, both the optical and mechanical properties of the containerboard filled with modified green mud were significantly enhanced. The results confirmed the role of ultrasonic treatment in carbonation coating of green mud and revealed the great potential of modified green mud in the field of paper filling.