Mechanisms of Phosphorus Removal by Recycled Crushed Concrete

Abstract

Due to urbanisation, there are large amounts of waste concrete, particularly in rapidly industrialising countries. Currently, demolished concrete is mainly recycled as aggregate for reconstruction. This study has shown that larger sizes (2–5 mm) of recycled concrete aggregate (RCA) removed more than 90% of P from effluent when at pH 5. Analysis of the data, using equilibrium models, indicated a best fit with the Langmuir which predicated an adsorption capacity of 6.88 mg/g. Kinetic analysis indicated the equilibrium adsorption time was 12 h, with pseudo second-order as the best fit. The thermal dynamic tests showed that the adsorption was spontaneous and, together with the evidence from the sequential extraction and desorption experiments, indicated the initial mechanism was physical attraction to the surface followed by chemical reactions which prevented re-release. These results suggested that RCA could be used for both wastewater treatment and P recovery.

Crushed Autoclaved Aerated Concrete (CAAC), a Potential Reactive Filter Medium for Enhancing Phosphorus Removal in Nature-Based Solutions—Preliminary Batch Studies

“…Therefore, reusing tobermorite-rich waste, such as the scrap granulate generated from the production of crushed autoclaved aerated concrete (CAAC) or from the demolition of facilities built with this material, can be an interesting approach regarding recovery of P from wastewaters [4,5]. In addition, reusing this material also helps to promote the reuse of energy and to preserve natural capital, as concrete is embedded with high energy and raw material [15].…”

“…CAAC is a highly available building material used worldwide, mainly for masonry, insulation or structure reinforcement (lintels and roof/floor and wall panels) [5,6]. Several authors have demonstrated the potential of reusing CAAC for P removal [5,6,10,[14][15][16]. For instance, estimations have shown that approximately 590 kg or 1.2 m 3 of CAAC would be required to treat wastewater for one year from a household of five persons [5].…”

Utilization of Lime Mud Waste from Paper Mills for Efficient Phosphorus Removal

“…Torit et al reported 80% phosphorus removal from domestic wastewater within 2 h with 5 g of calcinated eggshell in 1.7 mg L −1 of primary phosphorus concentration, which means the mass ratio of eggshell ash/phosphorus was about 2941 [43]. Deng et al introduced a mass ratio of recycled concrete aggregate/phosphorus of 100, and about 95% phosphorus removal efficiency with 24 h contact time was achieved [44]. Nawar et al determined that the removal efficiency of phosphorus ions from drinking water was 97% with a mass ratio of absorbent doses, alum sludge/phosphorus, of 50 within 30 min [45].…”

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

“…Concrete-based materials contain high levels of Ca and Mg, and the feasibility of using these materials for Pi absorption has been recently demonstrated, although the scale up has not been reported (Wang et al, 2014). Moreover, construction waste accounts for more than half of all industrial waste, and the use of waste concrete for phosphate absorption is promising (Deng and Wheatley, 2018). This waste concrete recycling method would also be environmental friendly and economical and provide improved phosphate retention (Deng and Wheatley, 2018).…”

“…Moreover, construction waste accounts for more than half of all industrial waste, and the use of waste concrete for phosphate absorption is promising (Deng and Wheatley, 2018). This waste concrete recycling method would also be environmental friendly and economical and provide improved phosphate retention (Deng and Wheatley, 2018).…”