دانلود رایگان مقاله انگلیسی حذف فلزات سنگین از فاضلاب با استفاده از فرآیند نفوذ-تراوش و جذب بر روی کربن فعال - اشپرینگر 2018

Abstract

Heavy metal pollution has become one of the most serious environmental problems nowadays. The removal of heavy metals from wastewaters has attracted a considerable attention because of their adverse efects on public health and ecosystems. The main objective of this work was to investigate the efciency of the coupling of infltration-percolation process with adsorption on activated carbon in the removal of heavy metals contained in urban wastewater efuents. The adsorption of heavy metals on a commercial sample of activated carbon was studied in a static mode. Several laboratory experiments made it possible to distinguish the optimum quantity of powdered activated carbon necessary to remove a large range of heavy metals. Results showed that the equilibrium of the adsorption was reached very quickly for cadmium (Cd2+), i.e., after 15 min of contact with the activated carbon. On the other hand, the equilibrium of zinc (Zn2+), lead (Pb2+) and copper (Cu2+) was achieved after 45 min. The withdrawal rates were 70.77% for Zn2+, 64.75% for Pb2+, 67.07% for Cu2+ and 78.42% for Cd2+. The adsorption isotherms determined for Zn2+, Pb2+, Cu2+ were of type I, while the shape of the Cd2+ curve showed a type II isotherm. These isotherms confrm the capacity of the powdered activated carbon to adsorb cadmium better than the other studied heavy metals.

Conclusion

The main objective of this work was to model and classify the type of adsorption equilibrium of the heavy metals studied by coupling the infltration-percolation and PAC adsorption processes. The experiments showed that the coupling of the two processes improves the purifcation of the secondary efuents. The infltration-percolation technique, applied at a laboratory scale column according to a 4-day feeding—3-day drying schedule using a hydraulic load of 0.27 m/day, appears to be a sustainable system for removing pollutants such as organic matter and ammonium. However, it is less efective regarding heavy metal reduction. Furthermore, activated carbon is an efective adsorbent which can contribute to the satisfactory elimination of micropollutants contained in urban wastewaters thanks to its high specifc surface area. Results demonstrated that the coupling of infltrationpercolation and adsorption on PAC processes increases the abatement rate of heavy metals. The adsorption isotherms showed that the adsorption of Zn2+, Pb2+ and Cu2+ is of type I, while the Cd2+ has a type II isotherm. This metal has undergone a multilayer adsorption which enhances its attachment and therefore its removal from wastewater.