Abstract
Iron (III) adsorption from aqueous solutions unto periwinkle shell carbon (PSC) was studied using batch experiments. Activated periwinkle shell carbon was prepared (pyrolysed at 300°C and activated with nitric acid) and characterized to determine its physiochemical properties. Batch adsorption experiments were conducted to investigate the effects of process parameters (contact time, particle size, carbon dosage and pH of stock solution) on adsorption rate. Adsorption kinetics was tested using pseudo first and second order models. Adsorption Isotherms were analyzed using the Langmuir, Freundlich and Temkin isotherms while Thermodynamics parameters such as Enthalpy change (ΔH°), Entropy change (ΔS°) and Gibbs-free energy change (ΔG°) were determined. Results showed that adsorption rate increase with increase in contact time, adsorbent dose and pH and decreased with increase in particle size. Batch adsorption Kinetics experiments revealed that the mechanism of adsorption followed pseudo-second-order kinetic model. Isotherm data showed that the Langmuir isotherm accurately described the adsorption data indicating that adsorption process was mainly monolayer on a homogeneous adsorbent surface. Thermodynamic parameters results showed that adsorption process was endothermic with Enthalpy change (ΔH°): 222.91 kJ/mol; a positive Entropy change (ΔS°) of 19.19 kJ/mol, indicating an increase in the degree of freedom (or disorder) of the adsorbed species and a negative Gibb’s free energy (ΔG°) at all temperature indicating that the adsorption process was spontaneous and favorable at high temperature.
Highlights
The contamination of groundwater with heavy metals iron has been reported [1]
Batch experiments were carried out to investigate the effect of some process parameters such as: contact time, particle size, adsorbent dosage and the pH on adsorption rate
The adsorption rate increased with increase in contact time, adsorbent dosage and pH of aqueous solution and decrease with increase in particle size
Summary
The contamination of groundwater with heavy metals iron has been reported [1]. Iron is slowly released into ground water as naturally occurring and weathering iron bearing minerals and rocks infiltrating through the underlying formations are dissolved in the water and accumulates in the aquifers that serve as sources of ground water. Various products of industrial and human activities: Industrial effluents, acid-mine drainage, sewage, landfill leachate and agricultural activities contribute iron to groundwater [2]. High content of iron in groundwater has been reported [3]. Iron is an essential mineral for human, concentrations in ground water above the stipulated safe allowable limit makes ground water turbid, affects its domestic use (taste, color, odor) and affects its industrial applications. Oxidation of dissolved iron in water converts it to a red-brown solid which stains laundry and plumping fixtures, glassware, enhances the growth of iron bacteria, which forms dark-colored slime layers on the inner side of pipes and enhance corrosion of water pipes; excess iron deposits in the heart muscle can cause heart failure as well as abnormal heart rhythms [4]
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