Abstract
Deterioration in soil–water environment severely contributed by heavy metal bioavailability and mobility on soil surface and sub-surface due to irrational increase in wastewater discharge and agrochemical activities. Therefore, the feasibility of adsorption characteristics of the soil is paramount in curbing the problem of micropollutant contamination in the farming vicinity. Soil from a farming site in a populated area in Enugu, Nigeria was collected and tested to measure the lead and cadmium contents using atomic absorption spectrophotometer (AAS). The adsorption potency of the ultisol soil was estimated for identifiable physicochemical properties by standard technique. The mean activity concentration of Pb2+ and Cd2+ was 15.68 mg/kg and 3.01 mg/kg. The pH, temperature, metal concentration and contact time adsorptive effect on the Pb2+ and Cd2+ uptake was evaluated by batch adsorption technique. The Langmuir, Freundlich and Temkin models were fitted into equilibrium adsorption data and the calculated results depict a better and satisfactory correlation for Langmuir with higher linear regression coefficients (Pb2+, 0.935 and Cd2+, 0.971). On the basis of sorption capacity mechanism of the soil, pseudo-second-order model best described the kinetics of both metal ions retention process. The results of the present study indicated that the soil being a low cost-effective adsorbent can be utilized to minimize the environmental risk impact of these metal ions.
Highlights
Composite structured soil medium constitute the environmental basis for plants and other biomass survival as well as interaction of minerals and organic matter in ionic formation being instigated by various industrial, agricultural and other anthropogenic activities
Among the metallic toxic inorganic micropollutants with unique properties heavy metals are natural elemental constituents of parent materials in rocks and sediments being needed by the soil in trace amount for optimum performance of plant physiological process (Emenike et al 2016) whereas the non-essential parts are venomous to plants and humans with increased toxicity in water, soil and air accumulations at very low concentrations tolerance management (Ezeudo 2014)
The soil sample is classified as sandy loam with slightly acidic pH value in aqueous solution and metals exist as free ionic species or as soluble organometals and are more bioavailable
Summary
Composite structured soil medium constitute the environmental basis for plants and other biomass survival as well as interaction of minerals and organic matter in ionic formation being instigated by various industrial, agricultural and other anthropogenic activities. Among the metallic toxic inorganic micropollutants with unique properties heavy metals are natural elemental constituents of parent materials in rocks and sediments being needed by the soil in trace amount for optimum performance of plant physiological process (Emenike et al 2016) whereas the non-essential parts are venomous to plants and humans with increased toxicity in water, soil and air accumulations at very low concentrations tolerance management (Ezeudo 2014) They form precipitates or complex ions with other compounds in mobile phase of the soil diffusing into the food chain infusing carcinogenic threat through translocation to plants.
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