Low-cost synthesis of high-performance polycarboxylic ether by Co 2+ -, Ni 2+ - and Zn 2+ -catalyzed H 2 O 2 -NaHSO 3 initiation system

As a new type of high-performance water-reducing agent, polycarboxylate ether (PCE) has excellent properties such as small dosage and high water reduction rate. However, it is still necessary to develop a synthetic process to improve the performance of PCE at a low cost. In this paper, Co 2+ -, Ni 2+ - or Zn 2+ -catalyzed H 2 O 2 -NaHSO 3 redox initiation system is designed as a new cost-effective composite initiator system to synthesize PCE(Co 2+ ), PCE(Ni 2+ ) and PCE(Zn 2+ ). The synthesized PCEs were characterized by FTIR, GPC, Zeta potential, XRD, TG, SEM and HPLC. Compared with PCE0 synthesized by H 2 O 2 -NaHSO 3 system without metal ion catalyst, FTIR and GPC data show that the molecular weights of PCE(Co 2+ ), PCE(Ni 2+ ) and PCE(Zn 2+ ) were slightly reduced without any functional group type changed. When the double bond retention rate of isopentenol polyoxyethylene ether (TPEG) is 94.34%, the conversion rate of TPEG catalyzed by Co 2+ , Ni 2+ or Zn 2+ is up to 93.82%, which is much higher than 77.34% of PCE0. Compared with PCE0, PCE(Co 2+ ), PCE(Ni 2+ ) and PCE(Zn 2+ ) have better dispersion and retention abilities, a 51-mm larger fluidity and a bigger early hydration rate of cement slurries. Interestingly, the water reduction rates of PCE(Co 2+ ), PCE(Ni 2+ ) and PCE(Zn 2+ ) are 13.7%-25.3% higher than that of PCE0.