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<p>Industrial wastewater often contains high concentrations of Cr(VI), posing serious environmental and health threats. This study introduces a novel approach to enhancing the adsorption performance of lignocellulosic materials through thermal chemical modification of water hyacinth using dilute H<sub>2</sub>SO<sub>4</sub> under mild (low-temperature) conditions, and then a microbial treatment step by a cellulolytic bacterium strain. The effects of modification time (0–50 h), acid volume/material ratio (3–11 mL/g), temperature (25–60 °C), and acid concentration (0.5–3% v/v) were systematically evaluated using a one-factor-at-a-time (OFAT) method and further optimized via Box–Behnken Design (BBD) coupled with response surface methodology (RSM). Under the optimal conditions (30 h, 5.5 mL/g, 45 °C, and 1.5% v/v H<sub>2</sub>SO<sub>4</sub>), the treated biomass achieved a maximum Cr(VI) adsorption capacity of 3.22 mg/g. Characterization using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) surface area analysis confirmed that the mild acid treatment effectively reduced cellulose crystallinity, and introduced abundant C = O and O–H functional groups, while the surface area (1.86 m<sup>2</sup>/g) remained unchanged. The zero point of charge (pH<sub>pzc</sub>) of treated water hyacinth (TWH) was determined to be 5. Adsorption followed the Langmuir isotherm (R<sup>2</sup> = 0.972) and pseudo-second-order kinetic model (R<sup>2</sup> = 0.9982), involving both intra- and extra-particle diffusion. Furthermore, the results revealed that microbial treatment with <i>Alcaligenes</i> sp. KHM19 for 6 days achieved a Cr(VI) removal efficiency of 95.42% and an adsorption capacity of 3.85 mg/g, which was approximately 1.2 times higher than that obtained by thermal-acidic modification alone. This integrated method, combining biological treatment with thermal chemical modification, represents a novel and sustainable strategy for efficient Cr(VI) removal from industrial wastewater.</p>

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Novel integrated acidic and microbial modification strategy to improve adsorption performance of water hyacinth

  • 期刊论文

  • 发表日期：

    2026年1月4日

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  • Nguyen Thi Hong,
  • Duong Duc La,
  • Chu Luong Tri,
  • Le Xuan Sinh,
  • Le Ngoc Thuan,
  • Ichiro Kamei,
  • Nguyen Thi Hoai Phuong,
  • Xuan-Duc Do,
  • Van-Hao Duong,
  • Le Duy Khuong

摘要

Industrial wastewater often contains high concentrations of Cr(VI), posing serious environmental and health threats. This study introduces a novel approach to enhancing the adsorption performance of lignocellulosic materials through thermal chemical modification of water hyacinth using dilute H2SO4 under mild (low-temperature) conditions, and then a microbial treatment step by a cellulolytic bacterium strain. The effects of modification time (0–50 h), acid volume/material ratio (3–11 mL/g), temperature (25–60 °C), and acid concentration (0.5–3% v/v) were systematically evaluated using a one-factor-at-a-time (OFAT) method and further optimized via Box–Behnken Design (BBD) coupled with response surface methodology (RSM). Under the optimal conditions (30 h, 5.5 mL/g, 45 °C, and 1.5% v/v H2SO4), the treated biomass achieved a maximum Cr(VI) adsorption capacity of 3.22 mg/g. Characterization using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) surface area analysis confirmed that the mild acid treatment effectively reduced cellulose crystallinity, and introduced abundant C = O and O–H functional groups, while the surface area (1.86 m2/g) remained unchanged. The zero point of charge (pHpzc) of treated water hyacinth (TWH) was determined to be 5. Adsorption followed the Langmuir isotherm (R2 = 0.972) and pseudo-second-order kinetic model (R2 = 0.9982), involving both intra- and extra-particle diffusion. Furthermore, the results revealed that microbial treatment with Alcaligenes sp. KHM19 for 6 days achieved a Cr(VI) removal efficiency of 95.42% and an adsorption capacity of 3.85 mg/g, which was approximately 1.2 times higher than that obtained by thermal-acidic modification alone. This integrated method, combining biological treatment with thermal chemical modification, represents a novel and sustainable strategy for efficient Cr(VI) removal from industrial wastewater.