Performance enhancement and optimization of photocatalytic cyanide degradation in aqueous solution using Zn (II) and Fe (III) oxides as nanostructure supported on activated carbon

Abstract

BACKGROUND: Cyanide is a toxic compound used in gold mining, steel, electroplating and chemical industries. In this research, different mole ratios of Fe 3+ /ZnO supported on powder activated carbon (PAC) in the presence of H 2 O 2 under UV irradiation were used to degrade cyanide contamination. The photocatalyst was characterized by XRD, XRF, FESEM, TEM and BET and response surface methodology was applied to assess the individual and interaction effects of several operating factors on cyanide degradation efficiency and to determine the optimization conditions. RESULTS: The results indicated that the average particle size of catalyst ranged from 20 to 60 nm. pH had the largest effect on response and there was interaction between initial cyanide concentration and pH. Decreasing the initial cyanide concentration and pH, while increasing the catalyst dosage, hydrogen peroxide concentration and irradiation time improved the cyanide degradation efficiency. The experimental result of cyanide degradation efficiency under optimum conditions ([CN] − = 250 mg L −1 , photocatalyst = 1.4 g L −1 , irradiation time = 180 min, pH=10, mole ratio of Fe 3+ /ZnO=6% and [H 2 O 2 ] = 300 mg L −1 ) was about 98%. Photocatalytic activity was maintained even after seven successive cycles. CONCLUSION: The synthesized reusable high activity nanostructure photocatalyst can be considered an applicable and environmentally friendly catalyst for the decontamination of cyanide-polluted water. CharacterizationDifferent analyses were applied to characterize the synthesized nanocatalyst. An X-ray diffraction (XRD) (BrukerD-8 Advance, Germany), was applied to determine the crystalline phase. X-ray fluorescence (XRF) was used to determine the chemical composition and structure of the chemical compounds (Bruker J Chem Technol Biotechnol 2017; 92: 2360-2368

Cyanide adsorption on activated carbon impregnated with ZnO, Fe2O3, TiO2 nanometal oxides: a comparative study

“…Further, modification of AC with other materials especially TiO 2 , ZnO, and Fe 2 O 3 significantly improved the adsorption capacity and the cyanide removal yield. Most of these modified activated carbonbased materials not only can be used as a promising adsorbent but also as a high photoactive catalyst (Eskandari et al 2017(Eskandari et al , 2019. The research findings also verify that an adsorption process benefits from using low cost and ecofriendly bioadsorbents prepared from agricultural waste materials as the studies of (Dwivedi et al 2016;Moussavi and Khosravi 2010) showed cyanide (100 mg/L) removal by using 1.5 g/L of pistachio hull waste as an effective bioadsorbent was obtained 99% after 1 h and cyanide was removed by 87 and 82% using 20 g/L of bioadsorbents of PAS and TGL after 2 h, respectively.…”

“…The further investigation of the results of Table 6 shows that while some methods of cyanide removal like ozone (O 3 ) injection only degraded cyanide by 30%, the combination of O 3 with activated carbon adsorption technology could substantially enhance the degradation efficiency as cyanide was removed completely in a combined treatment system (Sánchez-Castillo et al 2015). As can be seen in Table 6, the performance of an adsorption process with photolysis (UV) and H 2 O 2 was also compared and the results indicated that using activated carbon or modified activated carbon adsorbents was more beneficial to purify wastewater containing cyanide than using UV, H 2 O 2 or the combination of these two (UV/H 2 O 2 ) that only degraded cyanide by 12, 8 and 33%, respectively (Eskandari et al 2017). The comparison of adsorption process by photocatalysis implies that both remediation technologies have strong potential to remove cyanide effectively.…”

“…The comparison of adsorption process by photocatalysis implies that both remediation technologies have strong potential to remove cyanide effectively. The study of (Eskandari et al 2017) showed that the cyanide removal efficiency by adsorption and photocatalysis process using ZnO/Fe 2 O 3 /AC nanoparticles under the optimal conditions of [CN] − = 250 mg/L, pH = 10, Time = 3 h, [ZnO/Fe 2 O 3 / AC] = 1.4 g/L were 54 and 80%, respectively. However, in some studies photocatalysis methods were found to be far more effective.…”

“…The patterns of activated carbon (Fig. 1a) indicate the peaks at 2θ = 31.0° and 51.0° set of planes of the micrographitic structure (Eskandari et al 2017(Eskandari et al , 2019Ouzzine et al 2014). The (Asuquo and Martin 2016;Ghasemi et al 2016;Moussavi and Khosravi 2010) Kinetic models Equations Linear expression Plot Parameters…”

Comprehensive review and future perspectives on the photocatalytic hydrogen production

“…The third strategy consists of coupling two semiconductors. The oxidation of the sacrificial agent or H 2 O and the reduction of hydrogen can be carried out on one of the semiconductors, whereas the other one can contribute to (i) enhancing the separation and transport of the electron–hole pairs, (ii) sensitizing the photocatalyst to visible light or, (iii) acting as co‐catalyst such as CdS/TiO 2 or TiO 2 /PbS . If redox reactions occur one in each semiconductor, the structure is called a Z‐scheme.…”