Comparison of the efficiency of duckweed in heavy metal removal from aqueous solutions in combined and separate forms

Today, heavy metal contamination is a major environmental concern across the world. Some of the common heavy metal pollutants in industrial wastewater include lead, copper, cadmium, and nickel. This study aimed to compare the efficiency of duckweed in the removal of heavy metals from aqueous solutions in combined and separate forms. This applied, fundamental research was conducted based on empirical studies. Heavy metal solutions were prepared at the concentrations of 5, 10, and 25 mg/l, and duckweed (weight: 0.2, 0.4, 0.8, and 1.2 g) was added to the prepared solutions (100 ml). Plant weight in the combined solution was four times higher than the separate solution. After the contact time of five, 10, and 15 days, heavy metal residues in the solutions was measured using ICP-OES. According to the results, heavy metal removal from the separate solutions differed with the combined solutions. Both systems were compared in terms of the contact time, initial heavy metal concentration, and removal order. The obtained results indicated that the removal efficiency of heavy metals was higher in the combined solutions compared to the separate solutions. Increased initial concentration also reduced removal efficiency in the separate solutions, while the removal rate remained constant in the combined solutions. Moreover, the heavy metals in the combined solutions were removed within a shorter time. The removal sequence of the heavy metals from separate solutions was lead>cadmium>nickel>chromium at the maximum removal time. In the combined heavy metal solutions, such removal rate sequence was not observed.