Development and characterization of phosphate tailings-based humic acid slow-release fertilizer using ball milling sludge acid activation - Yinxin Xie; Qi Zhang; Deyi Yuan; Yingjie Hu; Caiyuan Guo; Muhammad Atif Muneer; Yafu Tang; Yanhui Xu; Fu Wan; Youzhi Yang (Process Safety and Environmental Protection, 2025)