Production of activated carbon from duckweed and its effectiveness in crystal violet adsorption.

With the increase in the use of paint in industrial areas, the rate of dye in wastewater is also increasing. Therefore, the adsorbents used to remove the dye in wastewater are gaining considerable importance. The potential of duckweed (DW) in adsorption of crystal violet (CV), a water-soluble and toxic organic dye, was investigated. Characterization of the adsorbent was made by FTIR, SEM and pHzpc (zero charge point) analyses, and the pHzpc value was 7.75 pH. The effects of temperature, contact time, initial dye concentration, adsorbent dose and solution pH on CV removal were determined. According to the results obtained, the optimum pH, initial dye concentration, adsorbent dose, temperature and contact time were 6 pH, 30 mg L⁻¹, 0.5 g, 30 ºC and 60 min, respectively. The adsorption data were best fitted with Freundlich isotherm (R² = 0.9714) and maximum adsorption capacity of 61.06 mg g⁻¹ was determined from the Langmuir isotherm. Adsorption of CV by carbonized duckweed (cDW) follows the pseudo-second-order kinetic model (R² ≥ 0.999). Thermodynamic results of the adsorption process show that adsorption can occur spontaneously (ΔG⁰ ≤ -5.302 kJ mol⁻¹) and that the process is endothermic (ΔHº = 5.92 kJ mol⁻¹). The results of this study showed that cDWs are cost-effective adsorbent for effective removal of crystal violet dye. [ABSTRACT FROM AUTHOR]