The adsorption characteristics of synthetic zeolite CR-100 in a fixed-bed system using continuous flow of groundwater containing elevated ammonia concentration were examined. The possibilities for adsorbent mass calculation throughout mass transfer zone using novel mathematical approach as well as zeolite adsorption capacity at every sampling point in time or effluent volume were determined. The investigated adsorption process consisted of three clearly separated steps indicated to sorption kinetics. The first step was characterized by decrease and small changes in effluent ammonia concentration vs. experiment time and quantity of adsorbed ammonia per mass unit of zeolite. The consequences of this phenomenon were showed in the plots of the Freundlich and the Langmuir isotherm models through a better linear correlation according as graphical points contingent to the first step were not accounted. The Temkin and the Dubinin-Radushkevich isotherm models showed the opposite tendency with better fitting for overall measurements. According to the obtained isotherms parameter data, the investigated process was found to be multilayer physicochemical adsorption, and also that synthetic zeolite CR-100 is a promising material for removal of ammonia from Northern Banat groundwater with an ammonia removal efficiency of 90%.
A pilot-scale study was performed to explore the possibility of the removal of natural organic matter (NOM) and arsenic from groundwater in the village of Melenci (Northern Serbia) using strongly basic, macroporous ion-exchange resin, commercially available as Amberlite IRA 958-Cl. The influences of the specific flow rate (SFR) and a broad range of contact times were studied using native groundwater and the same water pretreated with sodium hypochlorite (NaClO) for the oxidation of As(III) to As(V) and the degradation of NOM. The investigated SFR exceeded the manufacturer's recommended maximum value by up to ten times. In the range of SFR from 50 to 300 bed volumes per hour (BV/h), a higher efficiency of NOM removal was achieved in the absence of the oxidant, whereas at lower SFR and shorter contact times, the efficiency was higher when the water was pretreated. The arsenic removal from the oxidant-pretreated water was equally efficient at all SFR, whereas in the absence of the oxidant the efficiency was significantly lower and did not depend on SFR. The effectiveness of the resin illustrates the fact that the experimentally determined optimum SFR value of 30 BV/h is stated as the maximum in the manufacturer's specifications.
The objective of this work was to study the sorption behavior of the strongly basic and macroporous commercial resin IRA 958-Cl for the removal of natural organic matter (NOM) from groundwater in the Melenci settlement located near Zrenjanin (Northern Serbia). The investigation was performed in a pilot plant using native groundwater and the same water after chlorination with sodium hypochlorite. More efficient removal of NOM and arsenic was achieved without the addition of an oxidant under a wide range of working conditions. NOM removal was more efficient with the addition of the oxidizing agent compared with the overall efficiency for 2,900 bed volumes (BV) of treated water only during the initial phase of operation. Arsenic removal from chlorinated water was more efficient up to approximately 700 BV. At higher BV values, arsenic removal was up to two times more efficient with non-chlorinated water. The results obtained for the NOM sorption affinity to the resin indicated that it is possible to achieve a sorption capacity that exceeds the performance quoted by the resin manufacturer on several occasions.
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