Abstract
The contamination of surface and groundwater with phosphate originating from industrial, agricultural and household wastewater remains a serious environmental issue in low-income countries. Currently, demolished concrete is mainly recycled as aggregate for reconstruction and conventional wastewater treatment systems for removing phosphate are expensive and complex. In this study, we were aiming at testing crushed concrete as an efficient adsorbent for the removal of phosphate from aqueous solutions, obtained from the demolition of construction site. It can reduce pollution and landfill disposal by converting construction waste into valuable products and an alternative solution for phosphate removal. Batch adsorption experiments were conducted using phosphate solutions to examine the adsorption kinetic as well as equilibrium conditions. Results show that the phosphate adsorption of all absorbents follows the adsorption isotherms with a varying phosphate concentration from 3 mg/L to 18 mg/L, and the adsorption isotherms data are fitted well by Langmuir equation as compared with the Freundlich isotherm. The maximum phosphate adsorption (97.67 %) was obtained at a contact time of 120 min, an initial phosphate concentration of 10 mg/L, and a solution pH of 4. The pseudo second-order equation describes the experimental data has good agreement, with a correlation value of R2 = 0.99. The results obtained indicate that the environmentally available crushed concrete have a good adsorptive capacity for phosphate and shall be considered in future studies as test materials for phosphate removal from water in technical-scale experiment.
Highlights
Excessive phosphate discharge from manure, sludge sources, and chemical fertilizer applied to agricultural soils to runoff is the prominent source of water quality deterioration and nutrient enrichment
The specific surface area of crushed concrete was identified as 35 m2/m3
The crushed concrete was examined by EDS (ED3000) and composed of 56 % oxygen, 18 % Si, 10 % Carbon, 10 % Ca, 2 % Al, 2 % K, and 1 % Mg
Summary
Excessive phosphate discharge from manure, sludge sources, and chemical fertilizer applied to agricultural soils to runoff is the prominent source of water quality deterioration and nutrient enrichment. Municipal and industrial wastewaters are the main point sources for phosphate while run-off from agriculture is the dominant nonpoint source. According to the tolerable phosphate level in waters should not exceed 0.05 mg/L to maintain an ecologically sustainable status (Yadav et al, 2015). In such a case, to lower the phosphate loading in wastewater and runoff especially if local circumstances do not allow for advanced techniques such as membrane filtration became a challenge to local scientists and engineers
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