The objective of this research was to modify cotton (i.e. cellulose) fabrics forthe removal and recovery of lead (Pb(Ⅱ)) from aqueous solutions. Cotton fabricswere modified with 0.6 M citric acid solutions and characterized by infraredspectroscopy (ATR-FTIR) and potentiometric titrations. Also, adsorption,desorption, and kinetic experiments in batch systems were conducted.When modifying cotton fabrics with citric acid, density of functional groupsincreased up to 2.47 mmol/g in comparison with the non-modified fabric that had0.61 mmol/g. In addition, estimated equilibrium constants for the modified fabricscan be associated in part to carboxylic groups of the citric acid. The appearance ofcarboxylic groups on modified fabrics was also confirmed by ATR-FTIR analyses.Maximum adsorption capacity of Pb(Ⅱ) on modified fabrics, estimated withLangmuir isotherm, was 73.3 y 42.3 mg/g at pH 4 y 3, respectively, whereas nonmodifiedcotton fabrics did not adsorb Pb(Ⅱ) from water. Decrement in adsorptioncapacity suggests that Pb(Ⅱ) and H~+ ions compete for the same adsorption sites.On the other hand, it was possible to desorb around 92% of Pb(Ⅱ) previouslyadsorbed on the modified cotton with using 0.1 M HCl solutions since the chemicalequilibrium is shifted. Finally, adsorption kinetics can be predicted with a pseudosecondorder model.In summary, cotton fabric treated with 0.6 M citric acid has an adsorptioncapacity of Pb(Ⅱ) up to 3.5 times greater than the activated carbon, and theadsorbed metal can be recovered almost completely with 0.1 M HCl. These resultssuggest that modified cotton fabric is a highly competitive adsorbent for thetreatment of metal-containing wastewater.
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