Arsenate adsorption on waste eggshell modified by goethite, α-MnO2 and goethite/α-MnO2

Arsenic(V) sorption using chitosan/Cu(OH) 2 and chitosan/CuO composite sorbents

“…The intraparticle diffusion model provides a more comprehensive approach for defining of sorption mechanism, and the plot generally allows identifying different successive steps in the global process (Markovski et al, 2014 shows multi-linear sections ( Figure. AM3a, see Additional Material Section), i.e., three linear sections (on the plot q(t) vs. t 0.5 ) with fast kinetics in first step followed by the gradual attainment of equilibrium for both sorbents, and a pseudo saturation plateau. The multi-linear plot does not pass through the origin suggesting that the resistance to intraparticle diffusion is not the sole rate-limiting step: other mechanisms such as resistance to film diffusion and/or reaction rate, are probably involved in the control of uptake kinetics (Table 2, Figure AM5a, see Additional Material Section).…”

Adsorption Study of Arsenic Removal by Novel Hybrid Copper Impregnated Tufa Adsorbents in a Batch System

“…Detail explanation on the origin of presented adsorbents, properties, and obtained adsorption capacities is given in the Supporting Information. It was also recently shown that modification of egg‐shell calcite and synthesized calcite with goethite gave moderate adsorption capacity for As(V) removal: 33.38 mg g −1 and 21.00 mg g −1 which are lower values than those obtained for the T–Cu(A–C) adsorbents (Tab. ).…”

“…The higher values of the isoelectric point of the T–Cu adsorbents means that the positively charged surface is the driving force for arsenic adsorption over a wide pH range. Moreover, the moderate decrease in the pH PZC value after adsorption, from 8.1 ± 0.3 to 7.2 ± 0.4, indicated that specific arsenate adsorption is of major contribution to the overall adsorption process , that is, processes of surface complexation predominate over electrostatic interactions.…”

“…Special care was related to comparison with copper‐based , and iron oxides based adsorbents . Comparison with iron oxides based adsorbent was performed due to well‐known fact that modification of substrate with iron oxyhydroxides produce high affinity materials applicable for arsenic removal . Differences in the experimental conditions allow only a general qualitative overview of the analyzed adsorption data.…”

“…The Gibbs energy (Δ G 0 ), enthalpy (Δ H 0 ), activation energy ( E a ), and entropy (Δ S 0 ) of adsorption were calculated using the van't Hoff equations : where T is the absolute temperature (K) and R is the universal gas constant (8.314 J mol −1 K −1 ). The Langmuir sorption constant b was derived from the isotherm experiments.…”