Evaluation of Autoclaved Aerated Concrete Fines for Removal of Cd(II) and Pb(II) from Wastewater

Interactions of Cd2+, Co2+ and MoO42− Ions with Crushed Concrete Fines

“…Conversely, a significantly higher sorption capacity of 16.5 mg g −1 was reported for autoclaved aerated CCF exposed to solutions of up to 2000 ppm (solid:solution ratio 100 mg cm −3 ), which was also obtained using the Langmuir model [15]. This research involved a comprehensive investigation of the kinetics and equilibrium uptake of Cd 2+ ions but, again, the fate of the immobilised cadmium was not reported [15]. The superior sorption capacity of the autoclaved aerated cement may have arisen from the markedly higher concentration of the supernatant solutions, but may also be attributed to the crystalline nature of the major C-S-H phase in autoclaved cement (i.e., tobermorite), which is known to have a substantial ion-exchange capacity for Cd 2+ ions (~180 mg g −1 ) [32].…”

“…A similar maximum sorption capacity of 0.294 mg g −1 was reported by Damrongsiri [14] for 0.063-2.0 mm CCF using a Langmuir isotherm to model Cd 2+ -uptake (solid:solution ratio 25 mg cm −3 , with a maximum concentration of 4.0 ppm). Conversely, a significantly higher sorption capacity of 16.5 mg g −1 was reported for autoclaved aerated CCF exposed to solutions of up to 2000 ppm (solid:solution ratio 100 mg cm −3 ), which was also obtained using the Langmuir model [15]. This research involved a comprehensive investigation of the kinetics and equilibrium uptake of Cd 2+ ions but, again, the fate of the immobilised cadmium was not reported [15].…”

“…The linear form of the Langmuir isotherm, adapted for the uptake of species from solution by a solid substrate, can be represented in the following way [14,15,32]:…”

“…The mechanical crushing, sieving and sorting of concrete-based demolition waste, for the recovery and reuse of the aggregates, produces a large volume of fine (<5 mm), low-density, cement-rich material for which further market development is required [7,10,11]. In this respect, a number of recent studies has been carried out that seek to exploit the porous, absorbent and alkaline nature of the cement-rich fine material in the treatment of contaminated water [1,3,5,6,10,[12][13][14][15][16][17][18][19][20][21][22][23] and marine sediment [24][25][26]. Crushed concrete fines (CCF) are reported to be effective in the removal of various heavy metal species (AsO 3 3− [12], CrO 4 2− [12], H n PO 4 (3−n)− [20][21][22][23], Cd 2+ [13][14][15], Cu 2+ [10,13,17,18], Ni 2+ [13], Pb 2+ [10,13,15,16,18], Zn 2+ [10,13,18]), radionuclides ( 60 Co 2+ …”

“…In this respect, a number of recent studies has been carried out that seek to exploit the porous, absorbent and alkaline nature of the cement-rich fine material in the treatment of contaminated water [1,3,5,6,10,[12][13][14][15][16][17][18][19][20][21][22][23] and marine sediment [24][25][26]. Crushed concrete fines (CCF) are reported to be effective in the removal of various heavy metal species (AsO 3 3− [12], CrO 4 2− [12], H n PO 4 (3−n)− [20][21][22][23], Cd 2+ [13][14][15], Cu 2+ [10,13,17,18], Ni 2+ [13], Pb 2+ [10,13,15,16,18], Zn 2+ [10,13,18]), radionuclides ( 60 Co 2+ [1,5,6], 63 Ni 2+ [1,5,…”