Abstract
To study the structure-performance relationship, a series of nanostructured Fe-Cu binary oxides (FCBOs) were prepared by varying synthesis conditions. The obtained binary oxides were well characterized using X-ray diffraction (XRD), transmission electron microscope (TEM), Brunner-Emmet-Teller (BET), magnetic and Zeta potential measurement techniques. Both As(V) and As(III) sorption on the FCBOs were evaluated by batch tests. Results show that the surface structure and crystallinity of FCBOs are greatly dependent on preparation conditions. The crystallinity of FCBOs gradually increases as the synthesis pH value increasing from 9.0 to 13.0, from amorphous phase to well-crystalline one. Simultaneously, the morphology change of FCBOs from irregular agglomerate to relatively uniform polyhedron has been observed. The sorption of arsenic is greatly influenced by the crystallinity and structure of FCBOs, decreasing with increasing degree of crystallinity. The amorphous FCBO has higher surface hydroxyl density than well-crystalline one, which might be the reason of higher sorption performance. As(V) is sorbed by the FCBOs via formation of inner-sphere surface complexes and As(III) is sorbed through formation of both inner- and outer-sphere surface complexes. This investigation provides new insights into structure-performance relationship of the FCBO system, which are beneficial to develop new and efficient sorbents.
Highlights
Arsenic contamination has emerged as one of global environmental issues in the last decades due to its high toxicity (Smedley and Kinniburgh, 2002)
The main objectives of this study are 1) to synthesize a series of Fe-Cu binary oxides with different structure and crystallinity degree by varying the synthesis solution pH; 2) to characterize the morphology and crystallinity of as-synthesized binary oxides using a variety of techniques; 3) to evaluate the arsenic adsorption behavior and performance of binary oxides by batch tests; and 4) to investigate the structure-performance relationship of Fe-Cu binary oxide system
The intensity of peaks belonging to copper hydrated hydroxide, hydroxide and oxide decreases with an increase in synthesis pH value
Summary
Arsenic contamination has emerged as one of global environmental issues in the last decades due to its high toxicity (Smedley and Kinniburgh, 2002). Arsenic exists mainly in two inorganic forms as arsenate [As(V)] and arsenite [As(III)]. In view of the serious adverse effects of arsenic, a number of treatment techniques such as coagulation/precipitation, ion exchange, adsorption, membrane filtration and biological treatment, have been exploited for arsenic removal from drinking water and wastewater. Adsorption is commonly and extensively used, due to its simplicity in operation, high efficiency and cost-effectiveness (Mohan and Pittman, 2007; Hu et al, 2015). Various adsorbents have been developed and used for arsenic removal (Mohan and Pittman, 2007). Metal (hydr)oxides such as Fe (hydr)oxides (Sowers et al, 2017; Usman et al, 2020), feroxyhyte (Usman et al, 2021), Al oxides (Han et al, 2013; Mertens et al, 2016), TiO2 (Guan et al, 2012; Yan et al, 2015), ZrO2 (Hristovski et al, 2008; Cui et al, 2012; Shehzad et al, 2019), CeO2 (Srivastava, 2010; Li et al, 2012), CuO
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