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S. Mustafa ¹, M. Safdar ¹, Samad Yar Hussain ¹

Affiliations
1 National Centre for Excellence in Physical Chemistry, University of Peshawar, Peshawar, PK

Abstract

zn²⁺ ion adsorption from aqueous solution on α-Al(OH)₃ has been studied as a function of temperature. A simple method is described to evaluate the adsorption stoichiometry and apparent stability constants of the surface complex of the type [(AlO)_nM^2-n]. Thermodynamic parameters ΔG⁰, ΔH⁰ and ΔS⁰ for the process are also computed.

Keywords

Adsorption, Stability Constants, Thermodynamics.

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S. Mustafa ¹, Imtiaz Ahmad ¹, Dilara Begum ¹

Affiliations
1 National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar, PK

Abstract

The point of zero charge (PZC) of iron hydroxide has been determined between 30 and 60°C by measuring the distribution of the potential determining ions (H⁺, OH^-) at the hydroxide-solution interfaces for six different electrolytes (LiCl, NaCl, KCl, LiNO₃, NaNO₃ and KNO₃). For all these electrolytes a decrease in PZC has been observed. The cationic effect on the PZC of iron hydroxide (am) has been observed similar to lyotropic series i.e. Li⁺ > Na⁺ > K⁺. The investigated anionic effect for iron hydroxide is greater for nitrates than those of chlorides. Furthermore ΔH*, ΔS* and ΔG⁰* have been calculated by using Berube and DeBruyn equation.

Keywords

Point of Zero Charge, Iron Hydroxide-Solution Interface, Adsorption of Ions, Thermodynamics of Adsorption.

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S. Mustafa ¹, M. Safdar ¹, Samad Yar Hussain ¹

Affiliations
1 National Centre of Excellence in Physical Chemistry, University of Peshawar, PK

Abstract

Adsorption of Cu²⁺, Zn²⁺, Co²⁺, and Ni²⁺ from aqueous solution on α-aluminium hydroxide is studied as a function of temperature, using the method of potentiometric titrations. Adsorption is found to be endothermic in nature and follows the order Cu²⁺ > Zn²⁺ > Co²⁺ > Ni²⁺ in the temperature rangc 20-50 °C. The adsorption stoichiometry and apparent stability constants of the surface complex of the type [(AIO)_n M^2-n]are also evaluated. In case of Cu²⁺ and Ni²⁺ the process is favoured by positive values of the ΔS⁰, while in case of Cu²⁺ and Zn²⁺ the process is favoured both by the negative values of ΔG⁰ and positive values of ΔS⁰.

Keywords

Adsorption, Stability Constants, Thermodynamic Parameters.

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S. Mustafa ¹, A. Naeem ¹, N. Rehana ¹, S. Murtaza ¹

Affiliations
1 National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar, PK

Abstract

Potentiometric titrations of chromium(III) phosphate have been carried out in the presence of cu²⁺, Zn²⁺, Ni²⁺ and K⁺ ions from aqueous electrolyte solution as a function of concentration in the temperature range 303-323 K. The Cr(III)PO₄ is found to behave as a weak non no functional cation exchanger. pka of the exchanger has been determined and is found to be dependent upon the nature of the cations in the order Ni²⁺ > cu²⁺ = zn²⁺. The uptake of zn²⁺ by the chromium(III) phosphate is also investigated. It has been found that the uptake of zn²⁺ increases with the increase in both the pH (4-7) and temperature (303-327 K). The mechanism of uptake of zn²⁺ ions is found to be an ideal cation exchange.

Keywords

Ion Exchange Property, Chromium(III) Phosphate, Metal Ions.

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