Removal of copper by Azolla filiculoides and Lemna minor: phytoremediation potential, adsorption kinetics and isotherms.

Phytoremediation is an eco-friendly biotechnology with low costs. The removal of copper (Cu) from polluted water by the two floating plant species Azolla filiculoides and Lemna minor was observed and recorded. Plants were exposed to different Cu (II) concentration (0.25-1.00 mg/L) and sampling time (Days 0, 1, 2, 5 and 7). Both plants can remove Cu at 1.00 mg Cu/L water, with the highest removal rates of 100% for A. filiculoides and 74% for L. minor on the fifth day of exposure. At the end of the exposure period (Day 7), the growth of A. filiculoides exposed to 1.00 mg Cu/L was inhibited by Cu, but the structure of the inner cells of A. filiculoides was well organized as compared to the initial treatment period. Regarding L. minor, Cu at 1.00 mg/L negatively impacted both the growth and morphology (shrinking of its inner structure) of this plant. This is due to the higher accumulation of Cu in L. minor (2.86 mg/g) than in A. filiculoides (1.49 mg/g). Additionally, the rate of Cu removal per dry mass of plant fitted a pseudo-second order model for both plants, whereas the adsorption equilibrium data fitted the Freundlich isotherm, indicating that Cu adsorption occurs in multiple layers. Based on the results, both species can be applied in the phytoremediation of Cu-polluted water.

Response and capability of Scirpus mucronatus (L.) in phytotreating petrol-contaminated soil.

The greenhouse phytotoxicity experiment was conducted to analyse and assess the capability of Scirpus mucronatus (L.) in tolerating and removing petrol in contaminated soil. This research was conducted for 72 days by using 5, 10 and 30 g/kg petrol as soil contaminants. Results showed that the system planted with S. mucronatus (L.) had high potential to treat the 10 g/kg petrol-contaminated soil and had an average Total Petroleum Hydrocarbon (TPH) removal of 82.1%. At 5 and 30 g/kg petrol, the planted system removed 74.9% and 75.8% TPH, respectively. The petrol (10 g/kg) affected the plant growth positively, which was indicated by the increase in dry and wet weights throughout the research period. The removal of the TPH in the system was performed because of the interaction of plants and rhizobacteria. SEM showed that a high concentration of petrol (30 g/kg) affected the plant tissue negatively, as indicated by the altered structures of the root and stem cells. EDX results also confirmed that petrol was absorbed by the plant, as shown by the increased carbon content in the plant's root and stem after the treatment.

Role of Salvinia molesta in biodecolorization of methyl orange dye from water.

In the present study, the potential of Salvinia molesta for biodecolorization of methyl orange (MO) dye from water was examined. Six glass vessels were filled with 4 L of water contaminated with MO with three concentrations (5, 15, and 25 mg/L), three with plants and another three without plant as contaminant control. The influence of operational parameters, including initial dye concentration, pH, temperature, and plant growth, on the efficacy of the biodecolorization process by S. molesta was determined. Temperature and pH was in the range of 25-26 °C and 6.3 to 7.3, respectively. Phytotransformation was monitored after 10 days through Fourier transform infrared (FTIR) spectroscopy, and a significant variation in the peak positions was demonstrated when compared to the control plant spectrum, indicating the adsorption of MO. The highest biodecolorization was 42% in a 5 mg/L MO dye concentration at pH 7.3 and at 27 °C. According to the FTIR results, a potential method for the biodecolourization of MO dye by S. molesta was proven. Salvinia molesta can be successfully used for upcoming eco-friendly phytoremediation purposes for dye removal.

Plant-assisted remediation of hydrocarbons in water and soil: Application, mechanisms, challenges and opportunities.

Due to the increasing importance of diesel and petroleum for industrial development during the last century, petrochemical effluents have significantly contributed to the pollution of aquatic and soil environments. The contamination generated by petroleum hydrocarbons can endanger not only humans but also the environment. Phytoremediation or plant-assisted remediation can be considered one of the best technologies to manage petroleum product-contaminated water and soil. The main advantages of this method are that it is environmentally-friendly, potentially cost-effective and does not require specialised equipment. The scope of this review includes a description of hydrocarbon pollutants from petrochemical industries, their toxicity impacts and methods of treatment and degradation. The major emphasis is on phytodegradation (phytotransformation) and rhizodegradation since these mechanisms are the most favourable alternatives for soil and water reclamation of hydrocarbons using tropical plants. In addressing these issues, this review also covers challenges to retrieve the environment (soil and water) from petroleum contaminations through phytoremediation, and its opportunities to remove or reduce the negative environmental impacts of petroleum contaminations and restore damaged ecosystems with sustainable ways to keep healthy life for the future.