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

Abstract

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 (TiO2 NPs) and combined with EDTA (TiO2 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 TiO2 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 (Ct), bioaccumulation factor (BF), and removal efficiency (RE). The content of As and Cu in the plant showed that uptake depended upon TiO2 NP concentration, and the Ct, BF, and RE values were affected by concentration of TiO2 NPs in wastewater. Adding 200 mg kg−1 TiO2 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 TiO2 NPs enhanced the As content, Ct, 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 TiO2 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 TiO2 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 Ct, RE, and BF values increased due to applying individual TiO2 NPs and combined TiO2 NPs+EDTA. These results suggest that using TiO2 NPs for phytoremediation of contaminated water is helpful in enhancing As accumulation, whereas the L. minor is also a useful plant for Cu accumulation.