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<p>Calcium hydroxide has shown significant results in the removal of free fatty acids (FFAs), but the unsustainability of commercial calcium sources leads to the high cost of deacidification. In addition, the mechanism of the deacidification reaction is still unclear. In this context, this study employed eggshells as a low-cost calcium source to prepare a high-capacity deacidifier (2567&#xa0;mg·g<sup>−1</sup>) for the removal of FFAs from pork lard. Characterization of the deacidifiers was performed through FTIR, SEM, XRD and N<sub>2</sub> adsorption/desorption, and the effects of deacidifier dosage, reaction time and temperature on the deacidification efficiency were systematically investigated, while the kinetic and thermodynamic properties of the deacidification process were analyzed. Results showed that Ca(OH)<sub>2</sub>–850 reacts with FFAs to form insoluble calcium soaps, achieving a 90% FFAs removal rate from waste lard. Response surface methodology (RSM) was further used to optimize the deacidification parameters. The optimal results obtained for deacidifier dosage is 1.4 wt.%, for reaction temperature is 57&#xa0;°C and for reaction time is 11.3&#xa0;h, which reduced the acid value (AV) of acidic lard to 0.84&#xa0;mg KOH·g<sup>−1</sup> and increased the purity of biodiesel to 94.09%. The deacidification kinetics were consistent with the pseudo-second-order (PSO) chemisorption model. Thermodynamic analysis showed that the removal of FFAs was characterized by heat absorption (Δ<i>H</i> &gt; 0) and a spontaneous process (Δ<i>G</i> &lt; 0). This work confirms that waste eggshells can be effectively utilized as a sustainable calcium source in the field of biodiesel production, offering a promising approach for waste management.</p>

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Sustainable Ca(OH)2 deacidifiers derived from waste eggshells for free fatty acids removal: characterization, performance and thermodynamics

  • 期刊论文

  • 发表日期：

    2025年6月2日

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  • Yawei Wang,
  • Chao He,
  • Gang Li,
  • Xinxin Liu,
  • Liang Liu,
  • Youzhou Jiao

摘要

Calcium hydroxide has shown significant results in the removal of free fatty acids (FFAs), but the unsustainability of commercial calcium sources leads to the high cost of deacidification. In addition, the mechanism of the deacidification reaction is still unclear. In this context, this study employed eggshells as a low-cost calcium source to prepare a high-capacity deacidifier (2567 mg·g−1) for the removal of FFAs from pork lard. Characterization of the deacidifiers was performed through FTIR, SEM, XRD and N2 adsorption/desorption, and the effects of deacidifier dosage, reaction time and temperature on the deacidification efficiency were systematically investigated, while the kinetic and thermodynamic properties of the deacidification process were analyzed. Results showed that Ca(OH)2–850 reacts with FFAs to form insoluble calcium soaps, achieving a 90% FFAs removal rate from waste lard. Response surface methodology (RSM) was further used to optimize the deacidification parameters. The optimal results obtained for deacidifier dosage is 1.4 wt.%, for reaction temperature is 57 °C and for reaction time is 11.3 h, which reduced the acid value (AV) of acidic lard to 0.84 mg KOH·g−1 and increased the purity of biodiesel to 94.09%. The deacidification kinetics were consistent with the pseudo-second-order (PSO) chemisorption model. Thermodynamic analysis showed that the removal of FFAs was characterized by heat absorption (ΔH > 0) and a spontaneous process (ΔG < 0). This work confirms that waste eggshells can be effectively utilized as a sustainable calcium source in the field of biodiesel production, offering a promising approach for waste management.