Search

Spent refractory brick (SRB) generated from the steel industry has a high magnesium content. In this study, a procedure was developed to utilize SRB gravels for efficient recovery of phosphate and ammonia from high strength wastewater via struvite (MgNH 4 PO 4 ∙6H 2 O(s)) precipitation. Mg2+ and Ca2+ were first leached from SRB gravels using nitric acid solution. Ca2+ in the solution could inhibit struvite precipitation and was sequestered by dosing SO 3 2− to form calcium sulfite (CaSO 3 (s)). The resulting Mg2+-rich solution was then employed to initiate struvite precipitation for phosphate and ammonia recovery. The optimal precipitation was achieved with a molar ratio of [Mg2+]:[NH 3 –N]:[PO 4 3–P] = 2:1:2 at pH 9.5. The residual phosphate in the solution can be further removed via the precipitation of calcium phosphate minerals. Overall, 99.6% phosphate and 98.2% ammonia could be recovered and the treated wastewater could meet the discharging standards of ammonia and phosphate. The resulting solids, including calcium sulfite, struvite and calcium phosphate can be potentially used in the cement industry and agriculture sector to achieve sustainable recycle of spent materials. [Display omitted] • Spent refractory brick can provide Mg for struvite precipitation. • 99.6% phosphate and 98.2% ammonia could be recovered. • Treated wastewater could meet discharging standards in Taiwan. • Recovered CaSO 3 , struvite and Ca 3 (PO 4) 2 could be beneficially used. [ABSTRACT FROM AUTHOR]

Spent refractory brick (SRB) generated from the steel industry has a high magnesium content. In this study, a procedure was developed to utilize SRB gravels for efficient recovery of phosphate and ammonia from high strength wastewater via struvite (MgNH 4 PO 4 ∙6H 2 O(s)) precipitation. Mg2+ and Ca2+ were first leached from SRB gravels using nitric acid solution. Ca2+ in the solution could inhibit struvite precipitation and was sequestered by dosing SO 3 2− to form calcium sulfite (CaSO 3 (s)). The resulting Mg2+-rich solution was then employed to initiate struvite precipitation for phosphate and ammonia recovery. The optimal precipitation was achieved with a molar ratio of [Mg2+]:[NH 3 –N]:[PO 4 3–P] = 2:1:2 at pH 9.5. The residual phosphate in the solution can be further removed via the precipitation of calcium phosphate minerals. Overall, 99.6% phosphate and 98.2% ammonia could be recovered and the treated wastewater could meet the discharging standards of ammonia and phosphate. The resulting solids, including calcium sulfite, struvite and calcium phosphate can be potentially used in the cement industry and agriculture sector to achieve sustainable recycle of spent materials. [Display omitted] • Spent refractory brick can provide Mg for struvite precipitation. • 99.6% phosphate and 98.2% ammonia could be recovered. • Treated wastewater could meet discharging standards in Taiwan. • Recovered CaSO 3 , struvite and Ca 3 (PO 4) 2 could be beneficially used. [ABSTRACT FROM AUTHOR]