Use of diatomite for the removal of lead ions from water: thermodynamics and kinetics
2015
Bilgin, Melayib | Tulun, Şevket
The uncontrolled discharge of heavy metals generated by industrial processes into the environment threatens the living organisms. The widespread and unrestricted use of heavy metals results in their accumulation. Due to their adverse effects, heavy metals can be considered as an emergent pollutant group. In industrial wastewaters Pb²⁺ ion concentrations vary between 200 and 250 mg/L. Removal of heavy metals from wastewaters by an adsorption process can be economic and efficient, depending on the used adsorbent, in comparison with other methods. The present study aimed to examine the ability of a diatomite to remove lead (II) ions from aqueous solutions under various conditions. The effects of optimum adsorbent mass, contact time, different temperatures and pH were investigated. Pb(NO₃)₂ solution in a batch system was used in the present study. First, the specifications of the sorbent were determined and four different sorbent amounts were used. After this, the effect of contact time on the process of adsorption was determined. Finally the effect of different temperatures and pH on the adsorption was evaluated by using five different pH values and a temperature range from 20 to 40 °C. The maximum obtained removal efficiency was 98.09% by using 1.5 g/L diatomite for 2 min at pH 6 and 25 °C. The adsorption isotherm of lead (II) was described with Langmuir isotherm. The paper also discussed thermodynamic parameters, including enthalpy and entropy, and concluded that the adsorption was an endothermic process under natural conditions.
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