Precipitated droplets in-situ cross-linking polymerization towards hydrogel beads for ultrahigh removal of positively charged toxins

•A novel one-pot approach towards prepare hydrogel particles was presented.•Spherical hydrogel particles were prepared eco-friendly and fastly in only 40 s.•The particles showed ultrahigh removal capacity towards positively charged toxins.•The hydrogel particles were promising as reusable absorbent in wastewater treatment.