Comparative Assessment of Modified Bentonites as Retardation Barrier: Adsorption Performance and Characterization

Modified bentonites for anti–seepage system application has been attracting global attentions. At the same time, the performances of modified bentonite containing retardation barrier exposed to organic–heavy metal pollutants have not been fully reported. In this study, the adsorption performances (one of the key evaluation indicators of retardation barrier) of nine kinds of commonly used modified bentonites on multiple contaminants were comparatively investigated. The X–ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses were also performed to unravel the adsorption mechanisms. Results show that the adsorption of modified bentonites on phenol and Pb(II) follows the order of SB–16 > PVA > CTAB > APAM > CTAB + PAC > PAC > CPAM > CTAB + PAC > CTAB + CPAM + APAM. Among all the samples, the bentonite modified with SB–16 showed the highest adsorption capacities for phenol and Pb(II). The surfactant molecules inserted in the interlayer space of montmorillonite increase the substrate spacing, which changes the structural properties of the bentonite from hydrophilic to hydrophobic and increases the adsorption of organic contaminants. On the other hand, the polymer has functional groups such as hydroxyl and carboxyl that can form a spatial three–dimensional cross–linking structure on the bentonite surface, providing more adsorption sites for heavy metal ions. These findings indicate the potential industrial applications of modified bentonite in a contaminant barrier system.

Distribution and contamination assessment of heavy metals in soils and sediments from the Fildes Peninsula and Ardley Island in King George Island, Antarctica

Concentrations of heavy metals (Cu, Pb, Zn, Cd and Cr) in surface soils and sediments collected in 2008 from 37 sampling sites in the Fildes Peninsula and Ardley Island were detected by atomic absorption spectrometry. The total contents of Cu, Pb, Zn, Cd and Cr ranged, respectively, from 61.36 to 562.2 mg/kg, 0.52 to 1.95 mg/kg, 54.61 to 577.9 mg/kg, 0.04 to 3.76 mg/kg and 6.83 to 25.9 mg/kg in soils and from 58.55 to 498.3 mg/kg, 0.60 to 2.51 mg/kg, 56.22 to 345.9 mg/kg, 0.07 to 5.77 mg/kg and 7.76 to 39.5 mg/kg in sediments. The geo-accumulation index and the pollution load index were calculated to evaluate the environmental effects of heavy metal pollutants, Cu, Zn and Cd, in the study area. Soils and sediments from Ardley Island were found to be moderately polluted with the studied metals. Pearson’s correlation analysis and principal component analysis were applied to assess the distribution pattern and potential source of heavy metals. The results suggest that Cu, Zn and Cd in the study area originated from both the lithogenic sources and penguin guano, while Pb and Cr were probably derived from lithogenic sources.

Metal nanoparticles and its application on phenolic and heavy metal pollutants

The perpetual exposure of several manmade materials and their activities such as urbanization, industrialization, transportation, mining, construction, petroleum refining, manufacturing, preservatives, disinfectants etc., release various pollutants like organic, inorganic, and heavy metals which pollute the air, water, and soil. This poses various environmental issues which are relevant to the ecosystem and human wellbeing that intensify the implementation of new expedient treatment technologies. Likewise, phenolic and heavy metal pollutants find their way into the environment. These phenolic and heavy metals are toxic to the liver, heart and carcinogenic. Therefore, the removal of these kinds of pollutants from the environment is a highly challenging issue. As conventional treatment technologies have consequent drawbacks, new interests have been developed to remediate and remove pollutants from the ecosystem using metal nanoparticles (MPNs). To date, many researchers all over the world have been investigating novel approaches to enhance various remediation application technologies. One such approach that the researchers are constantly showing interest in is the use of nanomaterials with potential applications towards the environment. In this regard, MPNs like Copper (Cu), Nickel (Ni), Palladium (Pd), Gold (Au), Silver (Ag), Platinum (Pt), Titanium (Ti), and other nano metals are serving as a suitable agent to eliminate emerging contaminants in various fields, particularly in the removal of phenolic and heavy metal pollutants. This chapter discusses the mechanism and application of various MPNs in eliminating various phenolic and heavy metal pollutants from the environment.

Clogging and Water Quality Change Effects of Typical Metal Pollutants under Intermittent Managed Aquifer Recharge Using Urban Stormwater

Managed aquifer recharge (MAR) using urban stormwater facilitates relieving water supply pressure, restoring the ecological environment, and developing sustainable water resources. However, compared to conventional water sources, such as river water and lake water, MAR using urban stormwater is a typically intermittent recharge mode. In order to study the clogging and water quality change effects of Fe, Zn, and Pb, the typical mental pollutants in urban stormwater, a series of intermittent MAR column experiments were performed. The results show that the type of pollutant, the particle size of the medium and the intermittent recharge mode have significant impacts on the pollutant retention and release, which has led to different clogging and water quality change effects. The metals that are easily retained in porous media have greater potential for clogging and less potential for groundwater pollution. The fine medium easily becomes clogged, but it is beneficial in preventing groundwater contamination. There is a higher risk of groundwater contamination for a shallow buried aquifer under intermittent MAR than continuous MAR, mainly because of the de-clogging effect of porous media during the intermittent period.

Study on the Removal Efficiency of Heavy Metals in Flue Gas of Small Sintering Machines

Heavy metal pollutants such as Hg, Pb, Cr, and Cd contained in flue gas from the sintering equipment bring about environmental hazards. In this paper, 4 small sintering machines with different control technologies were selected, and the US EPA 29 method was used to analyze the emission concentration of heavy metals from the sintering machines, and the removal efficiency of the different flue gas control technologies on the of heavy metal pollutants was analyzed. The results show that the dry flue gas desulfurization combining baghouse dedusting method has high removal efficiency of heavy metals in flue gas, with mercury removal efficiency of 60.06%, Pb removal efficiency of 92.92%, Cd removal efficiency of 92.20%, Cr removal efficiency of 55.14%. The removal efficiency of heavy metals is obviously higher than that of conventional electrostatic precipitation combining wet desulfurization. This is mainly ascribed to those heavy metals are mainly concentrated in the fine particulate matters of the fly ash. Dust removal technology can effectively coordinate the control of Hg, Cr, Pb and Cd in the flue gas. The semi-dry desulphurization and baghouse dedusting technology can promote the enrichment of Hg and Cr in fly ash. The results of this study can provide theoretical guidance for the control of Hg, Cr, Pb, Cd and other heavy metal pollutants control in sintering equipment, and for flue gas ultra-low emission transformation.

Spatial Contamination and Potential Ecological Risk Assessment of Heavy Metals in Farmland Soil around Nonferrous Metal Smeltery in North China

Nonferrous metallurgy is an important source of heavy metal in the environment and consequently poses potential risks to ecosystems. The impact of smelting on the surrounding envi-ronment is a concern. In this work, the content levels of selected heavy metals—chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), and arsenic (As)—were investigated separately in soil samples collected around two nonferrous metal smelteries using inductively coupled plasma mass spectrometry (ICP-MS). The spatial distribution characteristics of soil metal pollutants was studied by ArcGIS methods and the potential ecological risks were assessed by the Hakanson potential eco-logical hazard index. The results show that soils were heavily polluted by Cr, Ni, Cu, Zn, Cd, Pb, and As. Their mean contents in soil around Smeltery A were 88, 62, 103, 1200, 1.4, 146, and 69 mg/kg, respectively, and those around Smeltery B were 86, 59, 83, 117, 0.53, 57, and 65 mg/kg, respectively. Their contents were obviously higher than the background values of soil Cr (68 mg/kg), Ni (31 mg/kg), Cu (22 mg/kg), Zn (78 mg/kg), Cd (0.09 mg/kg), Pb (22 mg/kg), and As (14 mg/kg). The distribution pattern in soil and risk assessment results show that the pollution surrounding the two smelteries reached intense and moderate ecological hazard and that the contribution of Cd and As was up to 87.05% and 82.59%, respectively. These results suggest that metal smelting makes a considerable contribution to soil pollution.