Assessing treatment of lead (Pb II) from industrial wastewater on dried bulbs of water hyacinth: adsorption capacity, isotherm and kinetic study

Abstract

Remediation through aquatic macrophytes treatment system for the removal of noxious contaminants from wastewater is an emerging environmental protection technique. The dried and acid-alkali treated bulbs of water hyacinth (WHB) having high porosity and O2-filled functional groups were utilised to treat Pb(II) from industrial wastewater. Characterisation of WHB with FESEM, XRD and FTIR exhibited the presence of several carboxyls, hydroxyl, ketonic, aldehydes and other O2-filled functional groups showing WHB adsorption with highest monolayer capacity of (Qm) 38.614 mg/g. WHB adsorption directed towards the pseudo-second order kinetics and Langmuir isotherm mechanism. The study also emphasised effective regeneration of WHB using HNO3, NaOH and vacuum dry. The bio-sorption mechanism was observed to be endothermic spontaneous reaction process, with ΔG decreased from -0.71 to -8.53 with increasing temperature. With optimised and controlled process conditions, only 5.0 g L−1 of WHB bio-sorbent could significantly treat about 85.3% of 100 mg L−1 of Pb(II) within 120 minutes at pH 7.0 and 30°C. Also a comparative optimisation study of ANN and RSM were used to predict the WHB bio-sorption bioprocess. Therefore, WHB have efficient potential to be commercially applicable as an environmental-friendly and economical bio-sorbent for treatment of Pb(II) from solutions and effluent from paint industry.