Arsenic Removal from Water by Novel Iron-Based Adsorbents
- Publication Type:
- Thesis
- Issue Date:
- 2022
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This thesis aims to develop novel iron-based adsorbents and investigate their performance in removing arsenic (As) from the water environment. Due to iron having a high affinity toward As ions, iron-containing adsorbents are deemed to be promising materials for removing As effectively from aquatic environments. In this study, 3 new iron-based adsorbents were successfully developed and investigated their ability to remove both arsenate (As(V)) and arsenite (As(III)) from synthetic and real contaminated groundwater. These were: (i) NLTT, a natural laterite obtained from natural iron–rich subsoil rock from Thach That, Hanoi, Vietnam through the simple production process; (ii) PPCI, an iron-impregnated biochar derived from combination of iron coating and slow pyrolysis carbonization processes of an agricultural waste product - pomelo peel; and (iii) Mn/Mg/Fe-LDH, a Mn/Mg/Fe-layered double hydroxides adsorbent obtained through the simple co-precipitation method. Results of this study show that these three studied iron-based adsorbents can remove both As(III) and As(V) effectively from water environments. Mn/Mg/Fe-LDH exhibited the highest adsorption capacity toward both As ions and could be used for very high polluted water sources. The Langmuir maximum adsorption capacities of Mn/Mg/Fe-LDH toward As(III) and As(V) were 56.1 mg/g and 32.2 mg/g, respectively. The maximum adsorption capacities of PPCI were 11.77 mg/g for As(III) and 15.28 mg/g for As(V), respectively. PPCI could be a new solution of reusing pomelo peel, a widespread agricultural waste, for remediating As from contaminated water. Referring to immediate practical applications, NLTT is the most suitable candidate for As removal in Vietnam’s rural areas due to its local availability, low cost (calculated commercial price of US$ 0.10/kg) and good As adsorption capacity (0.512 mg/g for As(III) and 0.580 mg/g for As(V)). NLTT has been successfully implemented as a filter media in both household and community filters in the Red River Delta, Vietnam. The long-term monitoring results show that both household and community filtration systems packed with NLTT could produce safe drinking water with As levels below the WHO and Vietnam’s drinking water limits after operating for 6–7 months. The exhausted NLTT adsorbent could be successfully managed by using solidification/stabilization method. The concrete bricks met the requirements of building materials as used in the construction industry. Although NLTT exhibited poorer adsorption capacities than PPCI and Mn/Mg/Fe-LDH, NLTT can quickly become a commercially viable As filter media. For PPCI and Mn/Mg/Fe-LDH, they have emerged as two practical promising adsorbents for removing As from water environments in the future.
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