向日葵盘低酯果胶对水中重金属铜离子的吸附性能

该研究探讨了向日葵盘中的天然低酯果胶对水溶液中重金属铜离子（Cu2+）的吸附性能，检测了果胶用量、果胶溶液的pH值、吸附温度、吸附时间及共存离子的影响作用。结果表明，随着果胶的用量增加，Cu2+的去除率不断升高，但吸附量先增大后降低。而吸附量和去除率均随吸附温度的升高和时间的延长先增大后不变、随果胶溶液pH值的升高先增大后降低，并受共存离子的影响，随二价金属离子含量的增加而降低。Cu2+初始质量浓度在0~200 mg/L范围时，利用Langmuir等温方程拟合得到向日葵盘果胶对Cu2+的最大吸附量为29.94 mg/g。热力学分析表明该吸附反应是自发的、熵值增加的吸热反应。动力学分析证明该吸附过程遵循准二级动力学方程，以静电吸引作用和络合作用为主要驱动力。可见，向日葵盘低酯果胶具有较强的Cu2+吸附性能，可作为一种安全、高效、环保的生物吸附材料应用在Cu2+废水的处理中。

Adsorption of Copper (II) Ions in Water by Low-methoxy Pectin from Sunflower Heads

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.