Facet-specific efficiency of hematite nanocrystals for arsenic removal in water-based solutions
The influence of hematite on the movement and alteration of arsenic in groundwater is significant.Investigating the facet-specific impact of hematite on As(Ⅲ)adsorption is crucial for comprehending the movement,alteration,and filtration of As(Ⅲ)in groundwater.This research involved the production of three variations of exposed hematite crystals with distinct crystal facets to eliminate As(Ⅲ)from water.Under ambient conditions,with an initial As(Ⅲ)concentration of 1 mg/L,pH 6.10,and an adsorbent concentration of 0.20 g/L,Hematite Nanorods(HNRs)demonstrated a maximum arsenic removal efficiency of 73.95％at adsorption equilibrium,exhibiting an adsorption capacity of 8.23 mg/g.The adsorption capacities of HNPs,HNCs,and HNRs were found to be 4.07 mg/g,4.46 mg/g,and 8.23 mg/g,respectively,with HNRs exhibiting the highest capacity.The quasi-first-order kinetic correlation coefficients R2 for As(Ⅲ)removal from HNPs,HNCs,and HNRs were 0.84,0.83,and 0.94,respectively.Additionally,the quasi-second-order kinetic correlation coefficients R2 for As(Ⅲ)removal were 0.92,0.89,and 0.98,respectively.The elimination process adheres to a quasi-second-order kinetic model,indicating that chemisorption governs the adsorption mechanism.The adsorption behavior conforms to the Langmuir model,signifying that As(Ⅲ)forms a monolayer on the hematite surface during adsorption.The optimal removal rate for As(Ⅲ)using hematite nanocrystals with distinct crystal facets is achieved at pH 6,particularly with HNRs displaying an efficiency of 81.67％.The removal of As(Ⅲ)by HNRs is significantly influenced by electrostatic adsorption and the complexation effects of coexisting F-and PO4-.As(Ⅲ)is eliminated through As(Ⅲ)—OH and Fe(Ⅲ)—O-As(Ⅲ)interactions on the surface of hematite nanocrystals.DFT calculations reveal that the adsorption energies(Ead)for hematite nanocrystals with {001 },{ 012 },and {110[planes are-8.27 eV,-3.48 eV,and-9.47 eV,respectively.As(Ⅲ)shows a preference for adsorption on the { 110} crystal plane,leading to the formation of Fe(Ⅲ)—O-As(Ⅲ)complexes on the hematite surface.This research introduces a novel method and approach to understanding the crystal plane-specific behavior of As(Ⅲ)migration and adsorption in groundwater by hematite.
basic disciplines of environmental science and technologyhematitearsenicfacet-dependent performanceadsorption
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