Abstract
Rapid industrialisation, technological development, urbanization and increase in population in the recent past coupled with unplanned and unscientific disposal methods led to increased heavy metal levels in water. Realizing the need for development of eco-friendly and cost effective methods, the present investigation was done for the adsorptive removal of copper from aqueous solutions with Dromaius novaehollandiae eggshell and chitosan composite. By one variable at a time method, the optimum contact time was found to be 60 min with an adsorbent dosage of 8 g/L at pH 6, initial adsorbate concentration of 20 mg/L and temperature 30 °C. The equilibrium data followed Langmuir and Freundlich isotherm models and pseudo second-order kinetics. The equilibrium adsorption capacity determined from Langmuir isotherm was 48.3 mg/g. From the Van’t Hoff equation, thermodynamic parameters such as enthalpy (ΔH°), entropy (ΔS°) and Gibb’s free energy (ΔG°) were calculated and inferred that the process was spontaneous, irreversible and endothermic. To know the cumulative effects of operating parameters, a three level full factorial design of Response Surface Methodology (RSM) was applied and the suggested optimum conditions were 7.90 g/L of adsorbent dosage, 20.2651 mg/L of initial adsorbate concentration and 5.9 pH. Maximum percentage of copper adsorption attained was 95.25 % (19.05 mg/L) and the residual concentration of the metal after sorption corresponded to 0.95 mg/L, which is below the permissible limits (1.3 mg/L) of copper in drinking water. The adsorbent was characterized before and after adsorption by SEM–EDS, FTIR and XRD. The FTIR analysis showed the involvement of carboxyl, hydroxyl and amino groups while XRD analysis revealed the predominantly amorphous nature of the composite post-adsorption and the peaks at 2θ angles characteristic for copper and copper oxide. The mechanisms involved in the adsorption of copper onto the adsorbent are chemisorption, complexation and ion exchange.
Highlights
Imperfect industrial activities like mining, electroplating, printing, photography, etc. and non-uniform technological development are the major factors contaminating the environment with toxic substances including heavy metals
The results showed that the percentage removal of copper increased briskly up to 60 min reaching 93.925 % (Fig. 1a)
Beyond 60 min, the % of adsorption remained the same indicating the attainment of equilibrium conditions
Summary
Imperfect industrial activities like mining, electroplating, printing, photography, etc. and non-uniform technological development are the major factors contaminating the environment with toxic substances including heavy metals. Non-uniform technological development are the major factors contaminating the environment with toxic substances including heavy metals. These metals pose a significant threat to the environment and the health of living organisms because of their toxicity due to accumulation in living tissues. Metal cleaning and plating baths, pulp, paper board mills, printed circuit board production, wood pulp production, fertilizer industry, etc. An ultra trace amount of copper is essential for living organisms but excess is detrimental. Ailments such as stomach upset and ulcers, liver and brain damage are caused by the excess concentrations of copper (Zhu et al 2009). Removal of excess copper from the contaminated waters is the most important environmental issue of worldwide concern since fresh water is the basic need for biotic community. Depletion of copper sources could be avoided by recovery
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