Water-insoluble hydrophilic polysulfides as microfibrous composites towards highly effective and practical Hg2+ capture

•Novel polysulfides (PS) were developed via molten sulfur and oxygenous co-monomers reaction.•Best PS has enhanced Hg2+ binding capacity (835 mg g−1) than conventional PS.•Electrospun PS with polyacrylonitrile (PAN) can be used as PS/PAN membrane filter.•PS/PAN is highly Hg2+-selective and can remove ~99.9% Hg2+ even at low feed.•PS/PAN is durable and recyclable with consistent performance for long-term use.