Using Recycled Concrete as an Adsorbent to Remove Phosphate from Polluted Water

Abstract

Phosphate pollution remains a significant hazard to terrestrial and aquatic ecosystems. We developed an economical and efficient method for phosphate adsorption on waste construction concrete modified with seawater. Compared with raw concrete materials, the phosphate adsorption capacity of seawater‐modified waste concrete was highly efficient, especially at low phosphate concentrations. The inflection point for seawater‐modified concrete was 0.66 and 1.22 mg L−1 for the raw material. The relative phosphate adsorption was 4.64 and 2.39 mg g−1, respectively. Phosphate removal was >90% over a pH range of 3 to 11 for the raw and modified materials. Chemical and physical analysis of the modified concrete indicated that Ca and Mg particles were uniformly sequestrated on the surface, and Ca was the determinant controlling phosphate uptake. Phosphate adsorption isotherms fit well using the Freundlich, Temkin, Elovich, Fowler–Guggenheim, and Hill–de Boer models and indicated that intermolecular forces in the concrete particles were enhanced by calcium oxides from seawater. This method can efficiently remove phosphate from polluted water and repurposes waste construction concrete. Core Ideas Phosphate adsorption capacity of modified waste concrete was highly efficient at low phosphate. Phosphate removal was >90% over a pH range of 3 to 11 for the raw and modified materials. Calcium was the determinant controlling phosphate uptake for seawater‐modified concrete. Intermolecular forces in the concrete particles were enhanced by calcium oxides from seawater.

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

“…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,…”

S-shaped adsorption isotherms modeled by the Frumkin–Fowler–Guggenheim and Hill–de Boer equations

“…This modeling approach has been discussed in some detail in the work of Chu and Tan [15]. The HDB model is handled in a similar manner as demonstrated in previous work [8][9][10][11][12][13][14]. However, only a limited number of studies have focused on extracting the three unknown parameters of the FFG model (qm, k1, and k2) or the HDB model (qm, k3, and k4) from S-shaped isotherm data.…”

“…( 6) or (7) for isotherm data analysis without disclosing the method used to estimate qm. Examples of recent studies following this approach include those conducted by Ramadoss and Subramaniam [8], Wu et al [9], Ali et al [10], Mathangi et al…”

White Cement as a Nontoxic and Eco-Friendly Adsorbent for Phosphate Adsorption/Desorption: Characterization, Optimization, and Modeling Studies

“…1 An innovation of our study is the evaluation of phosphate desorption from WC, since only Kuhn et al (2023) 18 and Cabral et al (2021) 31 conducted isotherms modeling using aerated concrete and red ceramic waste, respectively. Desorption of phosphate has been investigated from iron oxides, 23 sediments of different origins, 32 concrete aggregates, 33 and recycled concrete, 34 focusing on its recovery from highly concentrated wastewater.…”