Removal of cadmium from contaminated soil using iron (III) oxide nanoparticles stabilized with polyacrylic acid

The aim of this study is to evaluate the effect of Fe3O4 nanoparticle, stabilized with polyacrylic acid on cadmium removal from the contaminated soils. To investigate the effect of important parameters, including nanoparticle concentration, pH, contact time, and the ratio of contaminated soil mass to nanofluid volume, several batch tests were performed. The maximum removal rate (100%) of cadmium was obtained in the following conditions: nanofluid concentration = 500 ppm, pH = 6.5, contact time = 24 hr and the ratio of contaminated soil mass (gr) to nanofluid volume (mL) = 1:150. Results of selective sequential extraction tests showed that the distribution of cadmium in different fractions of the soil was carbonates, oxides and hydroxides, residual fraction, exchangeable, and organic matter respectively. The tendency of nanoparticles for removal of Cd2+ from the soil fractions was in the order of: exchangeable > carbonates > oxides and hydroxides > organic matter > residual

Removal of heavy metals from sediment using rhamnolipid

The interaction of heavy metals with sediments is complex and means are required to understand this matter more fully. Soil washing is among the methods available to remove heavy metals from sediments. This research was devoted to evaluating the performance of rhamnolipid for the removal of heavy metals, copper, zinc, and nickel, in batch and continuous flow configurations under different conditions, to investigate the mobility and availability of heavy metals by means of selective sequential extraction, and to find the mechanism for removal of heavy metals from the contaminated sediment obtained from the Lachine Canal, Quebec by using a rhamnolipid. The removal of heavy metals from sediments was up to 37% for Cu which was mostly from the organic, 13% of Zn which was mostly from the carbonate, and 27% of Ni which was mostly from oxide and carbonate fractions when rhamnolipid without additives was applied in the continuous flow configuration. By ion exchange experiments, complexation was found to be the major mechanism of removal for all three metals by rhamnolipid. Adding 1% NaOH elevated the role of ion exchange mechanism up to 67.1% for removal of zinc from the sediment. Rhamnolipid adsorbed to the sediment according to the Freundlich isotherm. The zeta potential of the sediment was measured at -24.3 mV for distilled water, -9.5mV for 2%, and -29.5 mV for 0.5% rhamnolipid. Scanning electron microscopy showed that washing with rhamnolipid does not change the texture of the sediment. Augmentation of the wetted surface area of the sediment improved the removal for all three metals (up to 3.5 times for copper), which emphasizes the role of this parameter in the removal process. A theory was established to explain the removal process of the metals, including wetting, contact of rhamnolipid to the surface of the sediment and detachment of the metals from the sediment. Rhamnolipid has proven its ability as a washing agent in heavy metals removal from sediments, but more research is required to improve the performance of the rhamnolipid before scale-up

Separation of Reactive Red 120 Dye from Aqueous Solution by NiFe2O4-SiO2/PVDF Nanocomposite Membranes

The discharge of dye-containing wastes by the dye-consuming industry causes irreparable damage to the environment and humans. Nowadays, the use of membrane separation technology is a new and applicable technology in dyes separation. However, membranes used in water and wastewater treatment suffer from problems such as permeability-selectivity trade-off as well as short life due to fouling. Therefore, in this study, we tried to improve the hydrophilicity and antifouling properties of polyvinylidene fluoride (PVDF) membranes by adding NiFe2O4-SiO2 nanocomposite and improve its performance in reactive dye separation from aqueous solution. For this purpose, first NiFe2O4-SiO2 nanoparticles were prepared by sol-gel method and then pure and NiFe2O4-SiO2/PVDF nanocomposite membranes were fabricated by wet phase inversion method and their performance was evaluated. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) methods. Membranes morphology, surface roughness, hydrophilicity of the membrane surface, separation performance, pure water flux, porosity and pore radius were characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), contact angle tests (CA), pure water flux test (PWF) and gravimetric methods, respectively. Aqueous solution containing 10-30 ppm reactive red 120 was used as test wastewater. The results of the contact angle analysis showed that by addition of 0.3 wt.% NiFe2O4-SiO2 nanoparticles to the polymer matrix, the membrane contact angle decreased from from 77.5° in the pure membrane to 51.7° in the nanocomposite membrane. It showed an increase in membrane hydrophilicity. AFM results showed that the surface roughness decreased as NiFe2O4-SiO2 content increased in PVDF matrix. It was also found that nanocomposite membrane containing 0.3 wt.% NiFe2O4-SiO2 nanoparticles has the best separation performance among the other fabricated membranes and this membrane can reject reactive red 120 dye from aqueous solution completely (99.5%)