Influence of nano-titanium dioxide particles (TiO2 NPs) on improving phytoremediation efficiency of As/Cu/Cd from copper mine wastewaters using Lemna minor

Phytoremediation technology is an appropriate and eco-friendly technique with high efficiency to reduce heavy metal hazards from a contaminated environment. This study analyzed the effects of individual titanium dioxide nano-particles (TiO 2 NPs) and combined with EDTA (TiO 2 NPs+ EDTA) on phytoremediation of arsenic (As), copper (Cu), and cadmium (Cd) from copper mine wastewater using Lemna minor. The experiments were exposed using different concentrations of TiO 2 NPs (200 and 300 mg kg −1 ) and EDTA (2 g kg −1 ) in seven treatments during 10 days. The content of As, Cu, and Cd was measured in plant tissues to calculate the total metal extraction ( C t ), bioaccumulation factor (BF), and removal efficiency (RE). The content of As and Cu in the plant showed that uptake depended upon TiO 2 NP concentration, and the C t , BF, and RE values were affected by concentration of TiO 2 NPs in wastewater. Adding 200 mg kg −1 TiO 2 NPs to mine wastewater significantly increased the plant biomass (66.5%), relative growth rate (42.2%), relative growth factor (33.9%), and tolerance index (39.2%) compared to the individual wastewater treatment. Adding 200 mg kg −1 TiO 2 NPs enhanced the As content, C t , and BF values to 382.5± 41.2 mg kg −1 , 122.1± 17.9 μg plant −1 , and 664.2±161.2, respectively, while the combined use of TiO 2 NPs+ EDTA and individual application of EDTA significantly decreased As uptake compared with wastewater treatment. For As, the RE (54.7%) and total absorbed (1786 kg ha −1 year −1 ) reached the maximum values following the application of 300 mg kg −1 TiO 2 NPs, which were 25.8% and 30.1% higher than the control wastewater treatment, respectively. Furthermore, the BF values in control wastewater treatment showed that L. minor was known as a hyper-accumulate plant for the Cu metal, whereas the C t , RE, and BF values increased due to applying individual TiO 2 NPs and combined TiO 2 NPs+EDTA. These results suggest that using TiO 2 NPs for phytoremediation of contaminated water is helpful in enhancing As accumulation, whereas the L. minor is also a useful plant for Cu accumulation.