Enhanced phosphate removal and potential recovery from wastewater by thermo-chemically calcinated shell adsorbents

Sabolc Pap, Paul P.J. Gaffney, Barbara Bremner, Maja Turk Sekulic, Snezana Maletic, Stuart W. Gibb, Mark A. Taggart

Research output: Contribution to journalArticlepeer-review

Abstract

Shell from the seafood processing industry is an under-utilised waste resource worldwide. Calcite, the major component of shell is commonly used in wastewater treatment for the removal of phosphorus (P). Here, mussel and oyster shell-based adsorbents (MSB and OSB) were used for removal of P as phosphate (PO43−) from aqueous solution and secondary wastewater, following preparation through chemical calcination at 700 °C. Batch adsorption experiments were carried out to identify the effects of various operating parameters (e.g., pH, dosage, contact time, initial concentration of P ions, co-existing ions), while a desorption study helped to understand the availability of the bonded P. The optimal contact time for PO43− removal was 120 min using both adsorbents with the dose at 200 mg. Characterisation of the adsorbent was performed using SEM-EDX, pHpzc, BET, FTIR and XRD. The XRD analysis showed that both calcite and lime were present on the surface of the shell particles. P was adsorbed effectively through inner-sphere complexation and surface microprecipitation mechanisms, while an enhanced maximum P adsorption capacity of 12.44 mg/g for MSB and 8.25 mg/g for OSB was reached. The Redlich-Peterson isotherm model fitted well with the equilibrium isotherm data (R2 ≥ 0.97) which also suggested a heterogenic surface. The desorption study (on the saturated adsorbent) found that ~97% of bonded P could be plant available in soil. These results suggest that a shell-based adsorbent can serve as a promising material for P removal from real wastewater effluent and subsequently could be used as a soil conditioner.

Original languageEnglish
Article number152794
JournalScience of the Total Environment
Volume814
DOIs
Publication statusAccepted/In press - 26 Dec 2021

Keywords

  • Adsorption mechanisms
  • Characterisation
  • Circular economy
  • Desorption
  • Seafood waste
  • Soil conditioner

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