Document Type : Original Article
Department of Civil Engineering, Sirjan University of Technology, Sirjan, Iran
In recent years, zero-valent iron has drawn a great attention in wastewater treatment and ground water remediation. It can effectively remove priority water contaminants, but there are some disadvantages in the use of nZVI particles, such as high tendency to agglomerate, lack of stability, secondary iron pollution, separation and recovery of the fine nZVI particles after utilization. Using supporting material for nZVI is a promising way to solve these problems. Clay minerals as abundant natural resources are appropriate candidates to act as supporting materials. In this study, the use of fibrous clays-supported nZVI composite for the remediation of contaminated aqueous solutions will be discussed.
Materials and methods:
Sepiolite and Palygorskite- nano zero valent iron composites were made using green tea extract. In order to determine sorption capacity of nZVI - sepiolite and palygorskite composites for phosphorous, cadmium and nickle based on isotherm models, different concentrations of these ions were equilibrated with the composites in 1% suspensions for 24 h. After adsorption, the supernatant liquids were filtered and the residual pollutants concentrations were determined.
Results and discussion:
Results showed that Langmuir and Freundlich models were the best models describing p sorption on both composites. The estimated maximum adsorption capacity of the Sep-nZVI and Pal-nZVI using the Langmuir model (qmax) was 11.38 mg P/g and 8.57 mg P/g . The cadmium adsorption data of both sorbents best fitted to the Langmuir, Fruendlich and dubinin–radushkevich models. Results clearly demonstrateD the much higher Cd sorption potential of sepiolite compared to palygorskite. Sorption capacities (qmax) of Sepiolite- nZVI and palygorskite nZVI composite for Ni were 11.14 and 32.3 mgr/gr, respectively. The Ni sorption affinity (KL) of palygorskite nZVI was also greater than that of Sepiolite- nZVI. The favorability of a sorption system can be predicted by the constant separation factor RL. In the current study, RL values for palygorskite nZVI and Sepiolite- nZVI were greater than zero and less than unity indicating favorable sorption of P, Cd and Ni onto the two composites.
Fibrous clays – nano zero valent iron can be used as efficient sorbents for phosphorus removal from urban wastewater and removal of cadmium and nickle from industrial wastewater due to their friendly environmental nature and high performance toward pollutants removal.