Bittern-impregnated sisal: An alternative magnesium source for phosphorus recovery through struvite precipitation?

• Autor(a) principal: Rodrigues, Denis Manuel
• Data de Publicação: 2022
• Outros Autores: Carvalho, Ana P., Fragoso, Rita, Hein, Thomas, Brito, Antonio Guerreiro De
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.5/28959
• topic: P recovery; sisal; precipitation; urine; fertilisers; bittern

Looking for cheaper and more transportable alternative magnesium(Mg2+) sources to envisage the full-scale application of downstream transfer of P recovery through struvite precipitation, sisal fibres were impregnated with bittern:water (B:W) ratio solutions 1:4; 1:5; 1:7 and 1:10. Two methods were attempted: the one-step method with a simultaneous Mg2+ release and struvite precipitation, and the two-step method with release and precipitation made separately. Sisal1:5 showed the highest recovery yield regardless of the method applied. The issue with the one-step method is that part of the crystals formed directly on the fibre surface, making their recovery harder. The two-step method using the sample impregnated with a 1:5 ratio resulted in highly pure struvite crystals, which are larger than those obtained with MgCl2⋅6H2O. Moreover, this method allows the retention of part of Cl in the fibres instead of releasing it into the solution, and crystals do not form over the fibres. This work shows that the use of Mg2+-impregnated materials is a poor alternative for urine with a high concentration of P (>600 mg P L 1) because it shows a poorer performance, 50 % P recovery, when compared to the direct use of bittern (>99 % P recovery yield). However, the higher struvite purity and the retention of part of the Cl make Mg2+-impregnated materials a potential solution to test in lower P concentrations (<300 mg P L 1). This study also opens several research opportunities regarding the application of Mg2+-impregnated material in P recovery through struvite precipitation.