Adsorption of multi-heavy metals onto water treatment residuals: Sorption capacities and applications

Abstract

Inherently formed iron-based water treatment residuals (WTRs) were tested as alternative sorbents for multi-heavy metal removal from synthetic solutions, contaminated sediments, and surface waters. The WTRs were mainly composed of iron (hydr)oxides and had a high BET surface area (170.7 m 2 /g), due to the presence of micro-and mesopores. The sorption capacity of 2 WTRs for As(V), Cd 2+ , Pb 2+ and Zn 2+ from synthetic solutions surpassed that of a commercially available goethite by 100-400% for single contaminant tests, and by 240% for total sorption in multi contaminant tests. The maximum sorption capacity of WTRs towards As(V), Pb 2+ and Zn 2+ was estimated by Langmuir equation fitting to range between 0.5 to 0.6 mmol/g, and their maximum sorption capacity for Cd was 0.19 mmol/g. WTRs performed significantly better than goethite for adsorption of cationic contaminants (Cd, Co, Ni, Pb, Zn) in the sediment tests, independent of the dosage or sediment sample. At the highest WTRs dosage (250 mg/g), concentrations of the cationic contaminants decreased by at least 80%, while approximately 40% removal was obtained with 50 mg/g dosage. Sorbent mixtures composed of WTRs with goethite, and with a clinoptilolite natural zeolite were used to reduce As leaching. The sorbent mixtures delivered the desired performance, with the natural zeolite performing better than the goethite as an amendment to WTRs. In addition, up to 90% removal of surface water contaminants was achieved with both fresh WTRs and the WTRs regenerated using 0.01 M EDTA.

The impact of recycling sludge on water quality in coagulation for treating low-turbidity source water

“…The experimental results showed that the removal efficiency of inorganic metal materials was significantly enhanced by the improved recycling sludge treatment. Chiang et al and Gibbons et al [19,20], using water treatment residuals (WTRs) as a sorbent to absorb multi-heavy metals, suggested that the WTRs were highly amorphous and contained significantly more micropores. In addition to the removal efficiency, cost is also an important factor in feasible production.…”

Wastewater engineering applications of BioIronTech process based on the biogeochemical cycle of iron bioreduction and (bio)oxidation

“…For example, precipitation of freshly produced flocs of Fe(OH) 3 obtained by oxidation of Fe 2+ can remove using adsorption, inclusion, and occlusion processes up to 90% of gross-alfa and 70% of gross-beta activity of groundwater containing such radionuclides as 226 Ra, 228 Ra, and 238 U [18,19]. Adsorption of such heavy metals as As, Cd, Co, Ni, Pb and Zn on ferric hydroxide particles is also well studied [20].…”

“…Iron-reducing bacteria are present in anaerobic digester of organic wastes. However, reduction of insoluble iron compounds does not affect methanogenesis [19,20], probably, because iron-reducing bacteria oxidize fatty acids, which are the final products of acidogenic fermentation that are not used in methanogenesis. Chelates of ferrous ions with soil humic acids or organic acids that are produced during ferric bioreduction can be oxidized by neutrophilic iron-oxidizing bacteria or can be used as electron donors in bacterial anoxygenic photosynthesis [1,2,3].…”

Comparison of metals extractability from Al/Fe-based drinking water treatment residuals

“…Studies have shown that WTRs can adsorb As (Makris et al 2006;Gibbons and Gagnon 2011;Castaldi et al 2014), Cr (Zhou and Haynes 2011), Hg (Hovsepyan and Bonzongo 2009), Pb (Zhou and Haynes 2011;Putra and Tanaka 2011), and Se (Ippolito et al 2009) from solution. Moreover, results of several investigations of WTRs use to mitigate metal pollution in soils indicate that amendment with WTRs can increase the stability of Cd, Ni, Zn, Pb, Cu, Cr, and As in soils (Brown et al 2005;Sarkar et al 2007;Fan et al 2011;Nielsen et al 2011;Wang et al 2012b;Chiang et al 2012;Elkhatib et al 2013).…”