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Published on: June 28, 2019
Simplex-Centroid mixture design applied to arsenic (V) removal from waters using synthetic minerals
Adriana Cristina Dias1, Maurício Paulo Ferreira Fontes1, Cesar Reis2
1Department of Soil Science, Universidade Federal de Viçosa, Viçosa, Minas Gerais, 36570-900, Brazil.
Arsenic (As) contamination in drinking water requires effective management. This study optimized mineral mixtures for arsenic removal, finding a specific combination of calcined layered double hydroxide (cLDH), poorly crystallized aluminum hydroxide (pAlHyd), and two-line ferrihydrite (2ℓFh) to meet World Health Organization standards.
Area of Science:
- Environmental Science
- Water Treatment Technologies
- Materials Science
Background:
- Arsenic (As) is a toxic and carcinogenic element posing significant risks to human health.
- Achieving the World Health Organization (WHO) standard for drinking water (0.010 mg/L) necessitates effective arsenic removal strategies.
- Current water management techniques require optimization for arsenic-contaminated sources.
Purpose of the Study:
- To determine the optimal mineral composition for maximum arsenic adsorption capacity (MAC-As) and minimum residual concentration (RC-As).
- To evaluate the efficacy of synthetic minerals, including poorly crystallized aluminum hydroxide (pAlHyd), calcined layered double hydroxide (cLDH), and two-line ferrihydrite (2ℓFh), in removing As(V) from water.
- To identify synergistic interactions between mineral components for enhanced arsenic removal.
Main Methods:
- A Simplex-Centroid mixture design (SCMD) was employed to systematically investigate various mineral compositions.
- Analysis of variance (ANOVA) and model predictions were used to validate experimental data and optimize mineral mixtures.
- Ternary diagrams were utilized to visualize and determine the ideal proportions of pAlHyd, cLDH, and 2ℓFh for arsenic removal.
Main Results:
- The Simplex-Centroid mixture design proved to be a reliable method for optimizing arsenic removal.
- Calcined layered double hydroxide (cLDH) demonstrated the highest arsenic adsorption capacity but resulted in residual concentrations exceeding WHO standards.
- Poorly crystallized aluminum hydroxide (pAlHyd) and two-line ferrihydrite (2ℓFh) achieved residual concentrations below the WHO standard, despite lower adsorption capacities.
- A synergistic effect was observed between the mineral components, influencing overall arsenic removal efficiency.
Conclusions:
- Optimal arsenic removal requires a balance between high adsorption capacity and low residual concentration, not solely maximizing adsorption.
- A specific mineral mixture comprising 75-90% cLDH, 10-20% pAlHyd, and 0-5% 2ℓFh is proposed for effective arsenic removal from drinking water.
- This optimized composition ensures compliance with WHO potability standards for arsenic levels.
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