A composite based on hydroxyapatite biocrystal and poly(aniline-o-phenylenediamine) copolymer for efficient removal of anionic dyes from wastewater

•Synthesis of novel composite is based on HAP@PANI@PoPD in situ co-polymerization.•The composite attained 99% dye removal at an initial concentration of 50 mg/L.•Optimum condition: 0.5 and 1 g/L for OG and TB dye; pH 2, 800 rpm of agitation speed.•The Temkin model was appropriate for describing the adsorption of OG dye.•The Redlich-Peterson and Toth models provided a good fit for the TB adsorption.•The composite could be regenerated five consecutive times with 80% efficiency.