Arsenic removal by copper-impregnated natural mineral tufa part II: a kinetics and column adsorption study
2019
This batch and column kinetics study of arsenic removal utilized copper-impregnated natural mineral tufa (T–Cu(A–C)) under three ranges of particle size. Non-competitive kinetic data fitted by the Weber–Morris model and the single resistance mass transfer model, i.e., mass transfer coefficient kfa and diffusion coefficient (Dₑff) determination, defined intra-particle diffusion as the dominating rate controlling step. Kinetic activation parameters, derived from pseudo-second-order rate constants, showed low dependence on adsorbent geometry/morphology and porosity, while the diffusivity of the pores was significant to removal efficacy. The results of competitive arsenic adsorption in a multi-component system of phosphate, chromate, or silicate showed effective arsenic removal using T–Cu adsorbents. The high adsorption rate—pseudo-second-order constants in the range 0.509–0.789 g mg⁻¹ min⁻¹ for As(V) and 0.304–0.532 g mg¹ min¹ for As(III)—justified further application T–Cu(A–C) in a flow system. The fixed-bed column adsorption data was fitted using empirical Bohart–Adams, Yoon–Nelson, Thomas, and dose–response models to indicate capacities and breakthrough time dependence on arsenic influent concentration and the flow rate. Pore surface diffusion modeling (PSDM), following bed-column testing, further determined adsorbent capacities and mass transport under applied hydraulic loading rates.
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