Abstract
The removal of Cr(VI) ions from aqueous solutions with wet pomace treated with laponite was investigated. A direct comparison with untreated biomass revealed an increase in both the rate of adsorption and the amount adsorbed. A cooperative interaction between the laponite platelets and biomass surface making more adsorption sites accessible was suggested. In this process, a key role is played by intraparticle diffusion. The experimental results indicate that intraparticle diffusion plays an important role in the adsorption process. A simple diffusion-binding model is presented to discuss the experimental results. The diffusion lifetime is linearly related to the adsorbent mass. The model combined with experimental results allowed us to estimate the average free path of a Cr(VI) molecule. Particularly, it was obtained that, in 1 dm3 of solution, the diffusion path increased by nearly 1 cm per gram of adsorbent. However, this did not imply that the amount of Cr(VI) removed decreased because the total number of adsorption sites also increased.
Highlights
The majority of consumable vegetable oils must be refined in order to eliminate undesirable substances affecting the quality of the oil
In recent years we investigated the ability of solid olive mill waste to adsorb heavy metals and in particular Cr(VI)
Intraparticle diffusion plays a key role in reaching the adsorption sites
Summary
The majority of consumable vegetable oils must be refined in order to eliminate undesirable substances affecting the quality of the oil. The quality of olive oil in terms of free fatty acids makes its refining unnecessary and the oil can be consumed as “virgin olive oil” [1]. The malaxation step aims to destroy the oil bodies (inner structure of the olives acting as tiny reservoirs) and liberate the oil. After the first pressing of the olives remains a mixture of the pulp and stones of olives, which constitute the solid olive mill waste. It was reported that olive mill waste has good adsorbing capacity of heavy metals [7,8,9]
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