TITLE:
Neem (Azadirachta indica) Leaves for Removal of Organic Pollutants
AUTHORS:
Muhammad B. Ibrahim, Sadiq Sani
KEYWORDS:
Batch Adsorption, Congo Red, Dye, Isotherms, Neem Leaves, Methyl Orange, Wastewater
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.3 No.2,
April
1,
2015
ABSTRACT:
Neem (Azadirachta indica) leaves was
employed in a batch adsorption technique for the detoxification of congo red
(CR) and methyl orange (MO) dyes from a single component model wastewater. The
adsorption efficiency of the leave was judged based on changes of parameters
like agitation time, adsorbent dosage, adsorbent particle size, and adsorbate
initial concentration and pH. Adsorbate concentration during the adsorption
process was monitored using T60-U UV-Visible spectrometer from TG Instruments.
While FTIR and SEM were employed to study the surface functional group and
morphological changes of the adsorbent before and after the adsorption process.
Percent adsorption increased with increase in agitation time (5 - 240 minutes),
adsorbent dosage (0.1 - 0.5 g), initial concentration (100 - 300mg/L), and with
decrease in particle size (≥75 μm to ≤300 μm) of adsorbent. The adsorption
processes were found to be pH-dependent, increasing or decreasing in acidic (pH
2 - 6) or alkaline (pH 8 - 12) range over the studied pH (2 - 12) range. The
correlation coefficient (R2 – values) ranging from 0.9359 - 0.9998 shows good
agreement of the experimental data for all the tested isotherms. The monolayer
maximum adsorption capacity for Langmuir’s qm (18.62 - 24.75mg/g) and Dubinin-Radushkevich,
qD (20.72 - 26.06mg/g) are comparable. Both Langmuir’s separation factor (RL)
and Freundlich constant (nF) suggests unfavourable adsorption of the dyes onto
the adsorbent. The mean free energy of adsorption, ?? (79.06 - 316.23 J/mol) calculated from Dubinin-Radushkevich
equation suggest a physical adsorption. Restricted range of values for heat of
adsorption, bT (?946.9 to 737.4 J/mol), was obtained from Temkin equation. Reduction
in band intensities and vibrational changes observed in FTIR spectra indicate
possible involvement of carbonyl (-C=O), carboxyl (-COOH), hydroxyl alcoholic (-OH)
and amino (-NH2) functional groups on the adsorbents’ surfaces during the
adsorption and interaction with the sulfonic acid groups (-SO3H) on the
adsorbate molecules. The difference in irregular and porous texture surface
morphology of fresh and dye-loaded adsorbents characterized the adsorption of
the dyes by neem leaves. The study shows that neem leaves are potential
alternative low-cost adsorbents for the effective removal of Congo red (CR) and
Methyl orange (MO) from wastewater.