Hydrothermal synthesis of Mg/Al-layered double hydroxide modified water hyacinth hydrochar for remediation of wastewater containing mordant brown dye

Abstract

A high-performance dye adsorbent of Mg/Al-layered double hydroxide modified water hyacinth hydrochar (MgAl@WH) was synthesized by a simple hydrothermal method. The surface functional groups, elemental composition, crystalline structure, and surface morphology of the prepared (MgAl@WH) were determined using different analytical techniques. The characterization results revealed that the (MgAl@WH) hydrochar surface offered more active adsorption sites, facilitating the mordant brown (anionic dye) adsorption, leading to its superior performance with much higher uptake capability (311.0 mg g⁻¹ at 298 K) than Mg/Al double hydroxide nanosheets (MgAl DLHs, 80.2 mg g⁻¹ at 298 K) and dried water hyacinth (WH, 10.0 mg g⁻¹ at 298 K). The adsorption behavior of MgAL@WH follows the pseudo second order kinetic model (R² = 0.999) and Langmuir isotherm model (R² = 0.999). Moreover, MgAl@WH bonded efficiently with mordant brown dye via hydrogen bonding and interlayer anion exchange with monolayer formation. Additionally, the recycling tests revealed that the MgAl@WH can be reused over 10 cycles without significant change in the removal efficiency. Based on the obtained findings, Mg/Al-layered double hydroxide modified water hyacinth hydrochar (MgAl@WH), for its economic and environmental benefits, has recently been used as an efficient adsorbent to remediate industrial wastewater containing anionic dyes.