Adsorption of Copper (II) Ions in Water by Low-methoxy Pectin from Sunflower Heads
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Abstract:
The adsorption capacity of natural low-methoxy pectin from sunflower heads on heavy metal copper ions (Cu2+) in aqueous solution was studied, and the effects of dosage, pH, adsorption temperature and time, and coexisting ions were investigated. Our results indicated that with increasing the pectin dosage, the removal rate of Cu2+ was continuously increased, whereas the adsorption capacity was initially increased and then decreased. Both adsorption capacity and removal rate increased initially and then remained unchanged with the increase in adsorption temperature or time. Similarly, both increased initially and then decreased with the increase in pH of pectin, whereas they decreased with the increase in concentration of divalent metal ions (coexisting ions) owing to the effect of coexisting ions. When the initial concentration of Cu2+ was in the range of 0~200 mg/L, the Langmuir isothermal equation was used to obtain the maximum Cu2+ adsorption capacity of pectin, which was 29.94 mg/g. Thermodynamic analysis showed that the adsorption process was a spontaneous and endothermic reaction with increasing entropy. Kinetics analysis revealed that the adsorption process followed the pseudo-second-order kinetic equation with electrostatic attraction and complexation as the main driving force. Thus, pectin derived from sunflower heads exhibits a strong Cu2+ sption capacity, making it a viable option as a safe, effective, and eco-friendly biosorption material for the treatment of Cu2+-contaminated wastewater.
