Removal of As(III) and As(V) from water using iron doped amino functionalized sawdust: Characterization, adsorptive performance and UF membrane separation

• Grafting with amino groups and iron impregnation are used to modify the sawdust.
• Grafted amino groups significantly enhanced iron loading amount.
• Mass transfer models are used to investigate the mass transfer resistance.
• UF membrane is used for the separation of adsorbent from Songhua river water.

Granular hydrated ferric oxides (HFO) have been proven to be a reliable material for As adsorption. However, it is difficult to directly apply it to the remediation of As contaminated rivers or lakes due to the small size and low hydraulic conductivity. Considering the demands for application in sudden water pollution remediation, a newly designed iron doped amino-functionalized sawdust (Fe-AFSD) presents effective As adsorptive performance from water. The maximum grafted amino group density was 0.96 mmol/g and the corresponding iron loading amount reached 17%. Fe-AFSD exhibited a much stronger affinity towards As(V) with a maximum adsorption capacity of 43.7 mg/g, while affinity towards As (III) was 10.1 mg/g at pH 7.0 ± 0.2. The kinetic curve can be well described by the pseudo-second-order model, indicating the chemical adsorption nature. The mass transfer model revealed that the internal diffusion is the rate-determining step for As adsorption on Fe-AFSD. The incorporated HFO played a key role for As(III) adsorption through surface complexing reaction, while grafted amino groups were mainly responsible for As(V) adsorption by electrostatic attraction. Furthermore, testing Fe-AFSD adsorbent with As contaminated Songhua river water showed suspended solids (SS) and total organic carbon (TOC) can be effectively eliminated after filtration process. The suspended Fe-AFSD can be effectively intercepted by UF membrane with no obvious permeate flux decline observed during three-day test using As contaminated Songhua river water sample.

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