Cadmium adsorption by coal combustion ashes-based sorbents—Relationship between sorbent properties and adsorption capacity

Removal of heavy metal ions from aqueous solution by zeolite synthesized from fly ash

“…These toxic metals, if not properly disposed, can be severely harmful to human health and the environment (Balsamo et al 2011;Bayat 2002;Hui et al 2005;Shi et al 2013). Various methods for the removal of heavy metals have been carried out, such as chemical precipitation, solvent extraction, ion exchange, reverse osmosis or adsorption, and so on (Fu and Wang 2011;Mohan and Gandhinathi 2009;Yaday et al 2013).…”

Deeper insights into fractal concepts applied to liquid-phase adsorption dynamics

“…A detailed description of the adsorbents chemico-physical and microstructural properties, together with the experimental protocols adopted for both sorbents activation and adsorption experiments can be found elsewhere [2,[19][20][21]. More relevant information is here recalled for the sake of clarity.…”

“…Adsorption is commonly recognized as an effective and versatile purification technology for the removal of numerous contaminants from liquid and gaseous effluents (such as organic compounds and heavy metals from wastewaters, and SO 2 , NO X , Hg and CO 2 from flue gas) due to the operating flexibility of the process, the potentially high selectivity towards a specific pollutant and the absence of by-products [1][2][3][4][5][6][7][8][9][10]. Industrial-scale adsorption processes are usually carried out either in cyclic batch systems, where an adsorbent fixed bed is alternately operated in adsorption and regeneration mode, or in continuous flow units with a countercurrent contact between the polluted stream and the adsorbent [6].…”

“…Langmuir and Langmuir-Freundlich models) or filmintraparticle diffusion mechanisms, or referring to the Statistical Rate Theory and to compact formulas differing in the functional form adopted to express the dependence of the removal rate on the process driving force (such as pseudo-first and pseudo-second order or exponential kinetic model) [11][12][13][14]. Even if compact kinetic models have been applied to numerous adsorption systems due to their simplicity determining computational time-saving, it has been pointed out that they are able to provide an optimum data fitting only in specific time ranges [2,11,15]. All the aforementioned models assume time-invariant kinetic constants or transport properties.…”

“…In particular, the results obtained from pseudo-first, pseudo-second order and exponential kinetic models in their classical and fractal-like forms were compared and analysed in the light of the sorbents granulometric and porosimetric properties. Experimental adsorption data and solid characterization results of reference for the modelling analysis and interpretation can be retrieved in recent papers published by this research group [2,[19][20][21].…”