Removal of Pb(II), Cr(III) and Cr(VI) from Aqueous Solutions Using Alum-Derived Water Treatment Sludge

Abstract

The sorption of Pb(II), Cr(III) and Cr(VI) from aqueous solution using alum-derived water treatment sludge was investigated using the batch adsorption technique. Samples of sludge from two separate water treatment plants were used (one where alum was used alone and one where it was used in combination with activated C). The sorption characteristics of the two samples were generally very similar. Sorption isotherm data for all three ions fitted equally well to both Freundlich and Langmuir equations. Maximum sorption capacity and indices of sorption intensity both followed the order: Cr(III)>Pb(II)>Cr(VI). Kinetic data correlated well with a pseudo-second-order kinetic model suggesting the process involved was chemisorption. Sorption was pH-dependant with percentage sorption of Cr(III) and Pb(II) increasing from <30% to 100% between pH3 and 6 whilst that of Cr(VI) declined greatly between pH5 and 8. HNO 3 at a concentration of 0.1 M was effective at removing sorbed Cr(III) and Pb (II) from the sludge surfaces and regeneration was successful for eight sorption/removal cycles. It was concluded that water treatment sludge is a suitable material from which to develop a low-cost adsorbent for removal of Cr and Pb from wastewater streams.

Sorption of Arsenic from Desalination Concentrate onto Drinking Water Treatment Solids: Operating Conditions and Kinetics

“…It was evident that the fractional uptake of arsenic significantly increased with the increasing DWTS dosage (Figure 1a,c), and reached a complete removal at high sorbent dosage with an abundant surface area and number of available sorption sites [31].…”

“…The chemisorption of arsenic onto DWTS could encompass the specific sorption and surface precipitation at high arsenic concentrations, significantly enhancing the level of arsenic sorption [31].…”

“…Arsenate species exist primarily as H 2 AsO 4 − (~3 < pH <~7) or HAsO 4 2− (~7 < pH <~11). The increase of the negative surface charge of DWTS caused by increasing pH may inhibit arsenic sorption because of electrostatic repulsion [31].…”

“…Arsenate species exist primarily as H2AsO4 − (~3 < pH < ~7) or HAsO4 2− (~7 < pH < ~11). The increase of the negative surface charge of DWTS caused by increasing pH may inhibit arsenic sorption because of electrostatic repulsion [31]. Due to the large amount of available sorption sites, pH has little impact on arsenic uptake in both deionized water and RO concentrate at DWTS dosage of 20 g/L with initial arsenic concentration of 20 mg/L (Figure 7).…”

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

“…There is also potential for WTRs use as a sorbent for metals and metalloids. 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).…”