赤铁矿纳米晶吸附水中砷的晶面依赖性

Facet-specific efficiency of hematite nanocrystals for arsenic removal in water-based solutions

赤铁矿会影响地下水砷的迁移转化,探索赤铁矿对As(Ⅲ)吸附的晶面依赖性对理解地下水As(Ⅲ)迁移转化和吸附去除具有重要意义。研究制备3种不同晶面暴露的赤铁矿纳米晶并用于水中As(Ⅲ)的去除,在室温条件下,当As(Ⅲ)初始质量浓度为1 mg/L、原始pH值为6.10、吸附剂质量浓度为0.20 g/L时,赤铁矿纳米棒(Hematite Nanoplates,HNRs)在吸附平衡时对As(Ⅲ)的去除率最高为73.95%,吸附容量为8.23 mg/g,吸附行为符合Langmuir模型,As(Ⅲ)在赤铁矿表面形成了单层吸附。不同晶面暴露赤铁矿纳米晶在pH值为6时对As(Ⅲ)的去除率最高,尤其是HNRs,可达到81.67%;HNRs去除水中As(Ⅲ)受共存离子F^(-)和PO_(4)^(3-);的静电吸附、络合效应影响较大。As(Ⅲ)通过在赤铁矿纳米晶表面形成As(Ⅲ)—OH、Fe(Ⅲ)—O—As(Ⅲ)进行去除,As(Ⅲ)能优先吸附在{110}晶面上并在赤铁矿表面形成Fe(Ⅲ)—O—As(Ⅲ)络合物。研究为赤铁矿对地下水中As(Ⅲ)迁移和吸附的晶面依赖性提供了新的思路和策略。

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 R^(2)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 R^(2)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 PO_(4)^(3-).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(E ad)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.