Abstract
The current study was designed to demonstrate the efficiency of selected zeolites in the immobilization of heavy metals and volatile organic compounds from water in the industrial area of Tito Scalo (Basilicata Region in Southern Italy). The efficiency of zeolite materials has been evaluated by analyzing real water samples, by a multi-technique approach. Gas chromatography (GC) and inductively coupled plasma optical emission spectrometry (ICP-OES) were selected for the detection of volatile organic compounds (VOCs) and heavy metals respectively, and then by thermal analysis (TG, DTA) and X-ray powder diffraction (XRD) to verify the presence of contaminants in the structural channels of the adsorbents. ZSM-5 zeolite (MFI topology) was suitable for volatile organic compounds, showing removal efficiencies 87%. 13X (FAU topology) was more selective for in situ abatements of heavy metals, with efficiencies up to 100%. After VOCs and heavy metals removal, structure refinements of loaded zeolites highlighted variations of both lattice parameters and extraframework content confirming the pollutants immobilization in the framework microporosities. The occurrence of these species was also confirmed by DTA curves showing different phenomena explained on the basis of the nature and number of extraframework species hosted in the zeolite micropores.
Highlights
volatile organic compounds (VOCs) were present in all the samples analyzed in a concentration range from 0.75 to 163 mg L−1, with an important contribution of 1,2-dichloroethylene and trichloroethylene which were identified in all the samples
ZSM-5 zeolite was shown to be suitable for volatile organic compounds, showing high removal efficiencies (>87%). 13X was more selective for in situ abatements of heavy metals with efficiencies up to 100%
The effective incorporation of VOCs and heavy metal species was confirmed by X-ray powder diffraction (XRD) structure refinements by the Rietveld method
Summary
Contamination of surface and groundwater is considered a global emergency due to the very fast development of industries, the badly conceived urbanization, as well as the agricultural practices.Being frequently a recipient for these contaminants, the aquatic ecosystem is seriously deteriorated and sometimes hopelessly compromised by the occurrence of natural and human-induced chemicals.A wide range of hazardous pollutants is released from nonpoint broadly distributed sources, including bioaccumulative and toxic chemicals (i.e., heavy metals such as lead, mercury, and chromium) and persistent and mobile organic compounds (PMOCs) (i.e., volatile organic compounds (VOCs), methyl-tertbutylether (MTBE), short-chain perfluoroalkyl acids (PFAAs), and tris(2-chloroethyl)Processes 2020, 8, 1519; doi:10.3390/pr8111519 www.mdpi.com/journal/processesProcesses 2020, 8, 1519 phosphate (TCEP)) [1,2,3,4]. We undertook a study of the industrial area of Tito Scalo which is designated as “Siti di Interesse Nazionale (SIN)” (contaminated Sites of National Interest) and, according to Italian law, its management is entrusted to the national authorities [6]. This contaminated site is characterized by the presence of groundwater containing chlorinated solvents (trichlorethylene, 1,2-dichloroethylene, 1,1-dichloroethylene, and vinyl chloride), metals (As, Fe, and Mn), and sulfates in concentrations above the reference threshold (CSC). Zeolites represent a benchmark in the area of porous materials, due to their efficiency as ion exchanger (i.e., heavy-ion removal) and organic adsorbent media
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