Abstract
For the first time, renewable and easy accessible pre-bleached spent coffee powder coated with polyethylenimine (PEI) and ferric ions (Coffee-PEI-Fe) was used for the successive adsorption of As(V), Cu(II) and P(V) ions from spiked water samples. Fully characterized coffee-PEI-Fe was employed for batch mode experiments. Kinetic regression analysis showed that the adsorption processes of As(V) and P(V) anions follows a pseudo-second-order model, while the adsorption of Cu(II) ions fit with a pseudo-first-order model. The maximum adsorption capacities estimated by Langmuir model for As(V), Cu(II) and P(V) ions were 83.3, 200.1, and 50.2 mg/g, respectively. The simulated results revealed that the internal diffusion is the rate-determining step for the adsorptions of As(V) and Cu(II) ions, while film diffusion is the mass transfer resistance for the adsorption of P(V) ions on the surface of coffee-PEI-Fe. The successive adsorptions of adsorbates were achieved through electrostatic attraction between adsorbent surface and adsorbates. The dynamic column adsorption behavior of the adsorbent was described by Thomas model, which showed a good agreement with the experimental values (qexp). The results presented in this paper could be used for developing efficient adsorbent from renewable materials for water purification.
Highlights
Large quantities of coffee beans are processed every year to quench the thirst for coffee drinkers around the world
In the current work, pretreated spent coffee powder is used as a renewable adsorbent and a new protocol of layer-by-layer adsorption is developed to enhance the efficiency of adsorption
The strong band at 1450 cm−1 of raw coffee grounds was assigned to -CH2 and -CH3 bending vibrations and/or the O-H bending peak due to the existence of phenols on the raw spent coffee powder surface[15,16]
Summary
Large quantities of coffee beans are processed every year to quench the thirst for coffee drinkers around the world. We hypothesized that adsorption of arsenic ions on the surface of the adsorbent lead to the development of a net negative surface charge, which could be used for the extraction of cationic pollutants such as Cu(II) ions from water and such alternating adsorption process can continue for a few adsorbates with opposite charges, before regenerating the adsorbent. Such successive extractions could be used in industrial cities where the effluents from each industry varies in chemical nature and composition. This layer-by-layer adsorption of alternatively charged pollutants from water may offer potential for reducing the overall cost of water purification process
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