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<p>This study investigates nonionic polyacrylamide (NPAM) as a flocculant for clarifying acid-leached liquors from aluminum sulfate production. These liquors contain colloidal de-aluminated metakaolinite that hinders solid–liquid separation. NPAM was fully characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, dynamic light scattering (DLS), and viscosity analysis, confirming its high molecular weight and mesoporous structure favorable for bridging-driven flocculation. Flocculation efficiency was evaluated under different dosages (0.1–1.0&#xa0;mg/kg), settling times (3–60&#xa0;min), and temperatures (25–60&#xa0;°C). Using response surface methodology (RSM), the optimal conditions—0.3&#xa0;mg/kg NPAM, 20&#xa0;min, and 25&#xa0;°C—achieved 95.3% turbidity removal, reducing suspended solids from 350&#xa0;g/L to 15.8&#xa0;g/L, representing a substantial improvement in clarification efficiency under highly acidic, high-solids conditions. Kinetic and isotherm modeling indicated a pseudo-second-order and Freundlich-type multilayer adsorption process, while thermodynamic parameters (ΔG° = − 30 to − 26&#xa0;kJ mol⁻¹; ΔH° = − 26 to − 13&#xa0;kJ mol⁻¹; ΔS° = 11–48&#xa0;J mol⁻¹ K⁻¹) confirmed spontaneous, exothermic, and entropy-driven behavior. Collectively, the results demonstrate that high-molecular-weight NPAM exhibits structure-dependent bridging behavior, enabling efficient and mechanistically validated flocculation of mineral suspensions under acidic conditions, with statistically optimized performance achieved at minimal polymer dosage.</p>

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High molecular weight nonionic polyacrylamide for flocculation of de-aluminated metakaolinite through production of pure aluminum sulfate: mechanistic and statistical insights

  • 期刊论文

  • 发表日期：

    2026年6月20日

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  • Marzouk Adel,
  • Entsar H. Taha,
  • Adel A. El-Zahhar,
  • Majed M. Alghamdi,
  • Ahmed M.A. El Naggar,
  • Esraa M. El-Fawal

摘要

This study investigates nonionic polyacrylamide (NPAM) as a flocculant for clarifying acid-leached liquors from aluminum sulfate production. These liquors contain colloidal de-aluminated metakaolinite that hinders solid–liquid separation. NPAM was fully characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, dynamic light scattering (DLS), and viscosity analysis, confirming its high molecular weight and mesoporous structure favorable for bridging-driven flocculation. Flocculation efficiency was evaluated under different dosages (0.1–1.0 mg/kg), settling times (3–60 min), and temperatures (25–60 °C). Using response surface methodology (RSM), the optimal conditions—0.3 mg/kg NPAM, 20 min, and 25 °C—achieved 95.3% turbidity removal, reducing suspended solids from 350 g/L to 15.8 g/L, representing a substantial improvement in clarification efficiency under highly acidic, high-solids conditions. Kinetic and isotherm modeling indicated a pseudo-second-order and Freundlich-type multilayer adsorption process, while thermodynamic parameters (ΔG° = − 30 to − 26 kJ mol⁻¹; ΔH° = − 26 to − 13 kJ mol⁻¹; ΔS° = 11–48 J mol⁻¹ K⁻¹) confirmed spontaneous, exothermic, and entropy-driven behavior. Collectively, the results demonstrate that high-molecular-weight NPAM exhibits structure-dependent bridging behavior, enabling efficient and mechanistically validated flocculation of mineral suspensions under acidic conditions, with statistically optimized performance achieved at minimal polymer dosage.