Structural characterizations of zinc-copper silicate polymer (ZCSP) and its mechanisms of ozonation for removal of p-chloronitrobenzene in aqueous solution

Zinc-copper silicate polymer (ZCSP) was synthesized and characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and nitrogen adsorption-desorption. The micro and mesoporous sample had columnar crystals and was mainly composed of amorphous silica (AS), hydroxylated copper (HC) and hydroxylated zinc (HZ). The ZCSP samples had high BET surface areas, high pore volumes and wide pore size distribution. The catalytic activity of ZCSP was investigated in terms of p-chloronitrobenzene (pCNB) and TOC removal. In the ozone/ZCSP process, 99.3% conversion of pCNB and 51.2% TOC were achieved in 15 min, respectively. The presence of tert-butanol (TBA) inhibited the degradation of pCNB in the ozone/ZCSP process and verified that the hydroxyl radicals (^[rad]OH) derived from ozone decomposition improved catalytic ozonation. The mechanism explaining the formation of ^[rad]OH on ZCSP surface was proposed. The HZ and HC composite had a positive impact on the oxidation affinity of pCNB. The zinc-copper oxide can act as Lewis acids and Brɵnsted bases to form surface hydroxyl groups. The hydroxyl groups were active sites that enhance ozone decomposition to form the ^[rad]OH. The ZCSP catalyst had good reusability and stability.