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Phosphorus removal from urban wastewater through adsorption using biogenic calcium carbonate

Publication . Santos, Andreia F.; Lopes, Daniela V.; Alvarenga, Paula; Gando-Ferreira, Licínio M.; Quina, Margarida J.

Phosphorus (P) removal from urban wastewater is increasingly relevant in the wastewater treatment sector. The present work aims to contribute to the study of the adsorption process as a P removal technology. Biogenic calcium carbonate from industrial eggshell waste prepared by milling and calcination was used as an adsorbent. Batch adsorption experiments were conducted using real wastewater with 40 mg P/L (orthophosphate), original pH 7.33, under stirring conditions (100 rpm). The adsorbent was characterized using SEM-EDS, XRD, and FTIRATR before and after adsorption. From an initial screening of calcination times (15, 30, 60, and 120 min) and considering a balance between P removal and energy saving, the adsorbent selected was eggshell calcined at 700 ◦C for 60 min. The Langmuir isotherms describe the experimental data with a maximum adsorption capacity of 4.57 mg P/g at 25 ◦C. The adsorption process reached equilibrium within 120 min for different dosages (5, 10, and 20 g/L at 25 ◦C). Batch experiments showed that SO42􀀀 , at a concentration of 2689 mg/L reduced the P adsorption selectivity for dosages ≤10 g/L at 25 ◦C. Characterization of the loaded adsorbent shows that P adsorption from real wastewater is mostly electrostatic attraction, with the contribution of ligand exchange and microprecipitation. The adsorption capacity and behavior of the selected adsorbent seem promising for P removal from urban wastewater compared with other low-cost adsorbents.

2024Artigo científico

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Fundação para a Ciência e a Tecnologia

Programa de financiamento

6817 - DCRRNI ID

Número da atribuição

LA/P/0006/2020