A novel colloid composited with polyacrylate and nano ferrous sulfide and its efficiency and mechanism of removal of Cr(VI) from Water

[Display omitted] •PAA can improve the dispersion and stability of nano-FeS.•The diameter of the PAA-n-FeS colloids was between 90.09 and 65.04 nm.•The removal quantity of Cr(VI) by PAA-n-FeS was 69.84 % higher than that of n-FeS.•The removal of Cr(VI) by PAA-n-FeS was mainly derived from its own reducibility. Nano ferrous sulfide (n-FeS) colloids show an excellent performance in the application of remediation in situ soil and groundwater. However, due to the interfacial effect and high reactivity of the nano sized FeS, n-FeS easy to agglomerate, which reduces their remediation efficiency. In this study, a novel composite colloid was synthesized using polyacrylic acid salt (PAA) and n-FeS. The PAA-n-FeS colloid was used to remove Cr(VI) in water remediation, and its removal mechanism and efficiency were explored. The results showed that the hydrodynamic diameter of PAA-n-FeS ranged from 65.04–90.09 nm and the zeta potential was from -27 to -54 mV at pH varying from 4.5–9.0. PAA was coated on the surface of n-FeS, which improved the dispersibility and stability of n-FeS by increasing the steric hindrance and electrostatic repulsion between n-FeS particles. Moreover, the Cr(VI) maximum removal amount PAA-n-FeS was 432.79 mg/g, which was significantly higher than that of n-FeS (218.29 mg/g) and PAA (12.32 mg/g). The mechanism of PAA-n-FeS removal of Cr(VI) was mainly derived from its own reducibility. The reaction products were mainly Cr(OH)3, Cr(III)-Fe(III), Cr2O3, and Cr2S3. This research not only finds a new stabilizer for preventing n-FeS agglomeration, but also provides a novel n-FeS composited colloid for promoting the practical application to Cr(VI) removal from water.