Yuliya E. Tyutereva,Peter S. Sherin,Zizheng Liu,Victor F. Plyusnin,Ivan P. Pozdnyakov
Quantum yields of indirect UVC photodegradation of p -arsanilic acid (a widely used phenylarsonic feed additive) caused by the photolysis of humic substances were measured. The acquired results demonstrate that the efficiency of such decomposition of p -arsanilic acid is comparable with that of its direct UVC photolysis due to the participation of active intermediates generated during the photolysis of humic substances. These results could be important for understanding the fate of p -arsanilic acid during an UVC disinfection of wastewaters containing natural humic substances.
Binxian Gu,Haijie Zhang,Meng Ye,Ting Zhou,Jianjian Yi,Qingsong Hu
As a kind of emerging contaminant, organoarsenic compounds have drawn wide concern because of their considerable solubilities in water, and the highly toxic inorganic arsenic species formed during their biotic and abiotic degradation in the natural environment. Thus, the effective removal and studying of the adsorption mechanism of organoarsenic compounds are of significant urgency. In this work, MnFe2O4and MnFe2O4/graphene were prepared through a facile solvothermal method. From the results of the Transmission Electron Microscope (TEM) characterization, it can be found that MnFe2O4nanoparticles were uniformly distributed on the surface of the graphene. And the specific surface area of the MnFe2O4/graphene was about 146.39 m2g−1, much higher than that of the MnFe2O4(86.15 m2g−1). The interactions between organoarsenic compounds and adsorbents were conducted to study their adsorption behavior and mechanism. The maximum adsorption capacities of MnFe2O4/graphene towards p-arsanilic acid (p-ASA) and roxarsone (ROX) were calculated to be 22.75 and 30.59 mg g−1. Additionally, the ionic strength, negative ions, and humus were introduced to investigate the adsorption performance of organoarsenic compounds. Electrostatic adsorption and surface complexation are the primary adsorption mechanisms on account of X-ray photoelectron spectroscopy (XPS) and the Fourier-transform infrared spectroscopy (FT-IR) analysis. This research extends the knowledge into studying the interaction between organoarsenic species and hybrid nanomaterials in the natural environment.Keywords:MnFe2O4;graphene;adsorption;p-arsanilic acid;roxarsone
A rational design of high-performance catalysts with peroxymonosulfate (PMS) activation and arsenic adsorption capacities for the removal of p -arsanilic acid ( p -ASA) is in high demand but remains a significant challenge. Herein, vacancies-rich metal–organic frameworks (MOFs) were constructed by room-temperature co-precipitation procedure, and the magnetic CoFe encapsulated in N -doped carbon nanotubes (CoFe- N -CNTs) were prepared using MOFs template by an annealing process under a nitrogen atmosphere. The synthesis conditions of CoFe- N -CNTs were optimized by tuning Fe/Co ratio and carbonization temperature. The CoFe- N -CNTs/PMS system showed favorable removal performance, achieving complete degradation of 46 μM p -ASA within 3 min and a total arsenic removal efficiency of 98% within 30 min at 0.1 g/L catalyst and 400 μM PMS. The degradation rate ( k obs ) and total arsenic removal efficiency towards p -ASA by CoFe- N -CNTs/PMS system were 6.7 and 2.7 times of those in the MOFs without vacancies-derived catalyst/PMS system, respectively. CoFe- N -CNTs/PMS system exhibited robust and efficient performance over a broad range of pH (4.5–9.0) and in different water matrices. Scavenging experiments and electron paramagnetic resonance (EPR) results demonstrated that non-radical singlet oxygen ( 1 O 2 ), sulfate radicals (SO 4 − ), hydroxyl radicals ( OH), and superoxide (O 2 − ) were involved in p -ASA decomposition. Electron transfer and direct oxidative transfer process (DOTP) also contributed to p -ASA degradation. High-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) analysis indicated that the arsenic moiety was cleaved from p -ASA in the form of As(III) and then rapidly oxidized to As(V). X-ray photoelectron spectroscopy (XPS) analysis indicated the removal of inorganic arsenic followed the mechanism of the inner-sphere complex. This study highlights the in-situ synthesis of CoFe- N -CNTs with outstanding activities for catalytic degradation and arsenic removal of organoarsenicals.
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