Ca(OH)2 coated nanoscale zero-valent iron as a persulfate activator for the degradation of sulfamethazine in aqueous solution

Abstract

In this work, a novel composite, Ca(OH) 2 coated nanoscale zero-valent iron (denoted as nZVI-Ca(OH) 2), was synthesized and used as an activator of persulfate for the degradation of sulfamethazine (SMT). The effects of sonication time during composite synthesis, pH, nZVI-Ca(OH) 2 dosage and typical groundwater components were investigated by batch experiments. Sonication time during the synthesis of the composite could affect the thickness of Ca(OH) 2 shell, however, it exerted no obvious effect on SMT removal by nZVI-Ca(OH) 2 activated persulfate. The initial pH also had insignificant effect on SMT removal in nZVI-Ca(OH) 2 /persulfate system. There was an optimum dosage of nZVI-Ca(OH) 2 composites for the activation of persulfate, and the SMT removal efficiency decreased at both higher and lower dosage. The efficient performance of nZVI-Ca(OH) 2 in synthetic groundwater was observed over a wide pH range (3-9). However, with the presence of high concentration of HCO 3or SO 4 2-, SMT removal was inhibited greatly due to the quenching of radicals by HCO 3or SO 4 2and the buffering effect of HCO 3-. In addition, the longevity of nZVI-Ca(OH) 2 was also investigated. Even after 30 days of aging in the air, Fe 0 could still be detected in nZVI-Ca(OH) 2. Despite some loss of Fe 0 , the composites kept high reactivity for activation of persulfate for SMT removal, which might be attributed to the excellent activation ability of amorphous iron oxides. To sum up, the Ca(OH) 2shell can protect the inner iron core and consequently prolong the lifetime of nZVI.

Aging of zero‐valent iron‐based nanoparticles in aqueous environment and the consequent effects on their reactivity and toxicity

“…The high surface to volume ratio and reactivity of nZVI makes the particles highly dynamic in aqueous environmental systems (Deng et al, ). The high reactivity of nZVI is related to its core–shell structure, which consists of a metallic iron (Fe 0 ) core encapsulated by a thin shell of iron oxides (Ling & Zhang, ; Rao, Mak, Liu, Lai, & Lo, ; Signorini et al, ; Sun, Li, Cao, Zhang, & Wang, ).…”

Removal of NO by Using Sodium Persulfate Solution: Catalyzed by Different Nanostructured MnO2

“…As mentioned above, hydroxyl ( • OH) and sulfate (SO 4 –• ) radicals both play dominant role in the NO removal process. Many works have been carried out to investigate the reaction mechanism of decomposing the solid persulfate. − Among the proposed mechanisms, the chain reaction for uncatalyzed decomposition of persulfate has been proven to be of persuasiveness and feasibility, which could also be extended to the case in which an oxidizable substance is present in the aqueous phase. , On the basis of the mechanism, the following equations could be assumed for NO removal process when coupled with some activation methods. ,,, With the purpose of further investigating the mechanism, the key free radicals, • OH and SO 4 –• , also were determined with EPR technique. From Figure , the free radicals with different signals are well captured with an EPR spectrometer under the experimental conditions.…”

“…38−40 Among the proposed mechanisms, the chain reaction for uncatalyzed decomposition of persulfate has been proven to be of persuasiveness and feasibility, 40 which could also be extended to the case in which an oxidizable substance is present in the aqueous phase. 41,42 On the basis of the mechanism, the following equations could be assumed for NO removal process when coupled with some activation methods. 24,30,40,43 S O chemical activation 2SO…”

Oxidative degradation of p-chlorophenol by the persulfate-doped Fe–Mn bimetallic hydroxide, the parametrical significance, and systematical optimization

“…Recently, some heterogeneous activators such as iron oxide, iron-based minerals, nanoscale zero-valent iron, etc. have been used to substitute aqueous Fe 2+ to potentially enhance the PS activation (Deng et al 2019, Park et al 2019. However, the pre-judgment effect of the control in releasing Fe(II) ions is still poor.…”