Hollow CoP/carbon as an efficient catalyst for the peroxymonosulfate activation derived from phytic acid assisted metal-organic framework.

The catalyst's composition and rationally designed structure is significantly interlinked with its performance for wastewater remediation. Here, a novel hollow cobalt phosphides/carbon (HCoP/C) as an efficient catalyst for activating peroxymonosulfate (PMS) was prepared. The ZIF-67 was synthesized first, followed by phytic acid (PA) etching and then heat treatment was used to get HCoP/C. The PA was used as an etching agent and a source of phosphorus to prepare HCoP/C. To analyze catalytic performance, another solid cobalt phosphides/carbon (SCoP/C) catalyst was prepared for comparison. In contrast to SCoP/C, the HCoP/C exhibited higher catalytic efficiency when used to activate PMS to degrade Bisphenol A (BPA). The results showed that about 98 % of targeted pollutant BPA was removed from the system in 6 min with a rate constant of 0.78 min-1, which was 4 times higher than the solid structure catalyst. The higher catalytic performance of HCoP/C is attributed to its hollow structure. In the study, other parameters such as BPA concentration, temperature, pH, and different catalyst amount were also tested. Moreover, the electron paramagnetic resonance (EPR) and radical quenching analysis confirmed that sulfate radicals were dominant in the HCoP/C/PMS system.

Core-Shell Prussian Blue Analogs with Compositional Heterogeneity and Open Cages for Oxygen Evolution Reaction.

Here, a reduction-cation exchange (RCE) strategy is proposed for synthesizing Fe-Co based bimetallic Prussian blue analogs (PBAs) with heterogeneous composition distribution and open cage nanocage architecture. Specially, bivalent cobalt is introduced into a potassium ferricyanide solution containing hydrochloric acid and polyvinyl pyrrolidone. The uniform PBAs with opened cages are formed tardily after hydrothermal reaction. Time-dependent evolution characterization on composition elucidating the RCE mechanism is based on the sequential reduction of ferric iron and cation exchange reaction between divalent iron and cobalt. The PBA structures are confirmed by electron tomography technology, and the heterogeneous element distribution is verified by energy-dispersive X-ray spectroscopy elemental analysis, leading to the formation of core-shell PBAs with compositional heterogeneity (Fe rich shell and Co rich core) and open cage architecture. When the PBA catalysts are used to boost the oxygen evolution reaction (OER), superior OER activity and long-term stability (low overpotential of 271 mV at 10 mA cm-2 and ≈5.3% potential increase for 24 h) are achieved, which is attributed to the unique compositional and structural properties as well as high special surface areas (576.2 m2 g-1). The strategies offer insights for developing PBAs with compositional and structural multiplicity, which encourages more practical catalytic applications.

Removal of reactive blue 19 dye by sono, photo and sonophotocatalytic oxidation using visible light.

An efficient sonophotocatalytic degradation of reactive blue 19 (RB 19) dye was successfully carried out using sulfur-doped TiO2 (S-TiO2) nanoparticles. The effect of various treatment processes that is sonolysis, photolysis, catalysis, sonocatalysis, photocatalysis, and sonophotocatalysis were investigated for RB 19 removal. S-TiO2 were synthesized in 1, 3 and 5 wt.% of sulfur by sol-gel process and characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX), UV-Visible diffuse reflectance spectra (DRS). The results confirm anatase phase of TiO2, porous agglomerate structure, and a red shift in the absorbance spectra of S-TiO2. The dye degradation was studied by using UV-Vis spectrophotometer at λ max=594 nm. The reaction parameters such as pH, catalyst dosage, initial dye concentration, ultrasonic power and effect of sulfur doping in different weight percent were studied to find out the optimum degradation conditions. Optimum conditions were found as: S-TiO2=5 wt.%, catalyst (S-TiO2 5 wt.%)=50mg, RB 19 solution concentration=20 mg L(-1), pH=3, ultrasound power=100 and operating temperature=25°C. The response of 5 wt.% S-TiO2 was found better than 1 and 3 wt.% S-TiO2 and other forms TiO2. The sonophotocatalysis process was superior to other methods. During this process the ultrasound cavitation and photocatalysis water splitting takes place which leads to the generation of OH. As reveled by the GCMS results the reactive blue 19 (20 mg L(-1)) was degraded to 90% within 120 min. The S-TiO2 sonophotocatalysis system was studied for the first time for dye degradation and was found practicable, efficient and cost effective for the degradation of complex and resistant dyes such as RB19.