Low-cost and high-performance materials or techniques that could synergistically remove inorganic heavy metals and organic pollutants in a simple manner are highly desired. Herein, we report a simple and facile strategy by converting poisonous heavy metals into photocatalyst for the in-situ photodegradation of organic pollutants employing steel slag-derived calcium silicate hydrate (CSH). The CSH was synthesized by alkali activation method and showed hierarchical structure and amorphous phase. And, the material exhibited excellent adsorption performance towards all selected heavy metals. After adsorption, the heavy metals were converted into the corresponding amorphous metal hydroxides on the surface of CSH. The resulting CSH-supported amorphous metal hydroxides can act as visible-light photocatalysts for the photodegradation of organic pollutants. The optimal results for the whole water purification route using CSH are > 100 mg/g adsorption capacity for Cu and ˜63% / 8 h photodegradation efficiency for methylene blue under visible light. The total cost for the whole route is < 0.1 $/g pollutants, much lower than traditional technologies. The strategy using steel slag derived-CSH not only meets the requirements for high-performance and low-cost materials, but also resolves the challenging issues of developing an all-in-one treatment for heavy metal ions and organic pollutants, which will be of great significance to wastewater purification.