Photocatalysis with solar energy: Sunlight-responsive photocatalyst based on TiO2 loaded on a natural material for wastewater treatment

•High rate of photocatalysis under solar light.•Photocatalysis combining economical and sustainable components including TiO2, black volcanic ashes and solar light.•TiO2 nanoparticles loaded on a natural material (black volcanic ashes).•Catalyst can absorb both UV and visible light.•Photocatalyst in particles for eliminating the complex liquid/powder separation process for wastewater treatment.