Abstract:
Water hyacinth (Eichornia crassipes) is a hazardous and fast-growing invasive aquatic
species for which international concern has been risen due to its environmental influence.
Textile industries are released large amount of toxic and hazardous pollutant of dyecontaining wastewater that highly degrade the environment.
The aim of this study was removal of Azo-dye from textile wastewater by graphene
composite bio-char synthesized from water hyacinth stem. Temperature (350, 450, and
550℃), and time (30, 40, and 60 min) were considered as a factor for the synthesis of
graphene-composite biochar using pyrolysis process and oxidation reaction. Temperature
(25, 30, and 35 ℃ ), pH (4, 7, and 10), and flow rate (3, 4.5, and 6 ml/min) were also
considered as factors to analyze the adsorption efficiency of graphene composite biochar
for azo-dyes removal from textile industries effluents using fixed bed column. The
characterization of graphene-composite biochar was performed using FTIR, SEM, XRD,
and BET surface area.
In this study, the maximum adsorption efficiency of graphene-composite biochar (99.91%)
was found at pH-10, 25℃, and 3ml/min whereas the minimum adsorption efficiency
(35.06%) was also found at pH-4, 25℃, and 3 ml/min. From the adsorption kinetics, the
pseudo second order (PSO) was better fitting rate-limiting and controlling adsorption
model which explicating that the adsorption was the chemisorption process, and the
Langmuir adsorption isotherm was better fitting adsorption isotherm model, and describes
the adsorption was a monolayer adsorption process.
From the thermodynamics analysis the ΔG was negative, while ΔH, and ΔS were positive,
those describe that the adsorption process was spontaneous, endothermic, and the
adsorbent has a high affinity for the adsorption of azo-dyes. Generally, graphenecomposite biochar was significant for dyeing-waste water treatment with an efficiency of
99.91% using fixed bed column and easily regenerative adsorbent with regenerative
efficiency of (99.897%).
Keywords, Water Hyacinth; pyrolysis; graphene containing bio-char; adsorption;