PERFORMANCE EVALUATION OF TREATED RICE HUSK ACTIVATED CARBON IN WATER TREATMENT AND REMOVAL OF PHENOL
PERFORMANCE EVALUATION OF TREATED RICE HUSK ACTIVATED CARBON IN WATER TREATMENT AND REMOVAL OF PHENOL
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Date
2015-04
Authors
MOHAMMAD, YAHAYA SAYYADI
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Abstract
Rice husk, a potential source of activated carbon, is locally available in Nigeria but
underutilized thereby constituting solid waste menace in the environment. Incidentally,
large volume of wastewater containing high concentrations of toxic contaminants such
as phenol and other contaminants are continuously being generated as a result of
increased industrial activities. Agricultural waste materials including rice husk, when
suitably modified could serve as activated carbon for efficient removal of wastewater
contaminants. In this study, rice husk activated carbon was produced by carbonization
followed by activation with phosphoric acid. Batch adsorption experiment was
conducted on effect of process variables (carbonization temperature, initial phenol
concentration, adsorbent dosage, contact time, solution pH and temperature) on the
adsorption of phenol onto rice husk activated carbon. Equilibrium isotherm, kinetics
and thermodynamics of the adsorption process were studied. Response surface
methodology was then employed for modeling and optimization of the process
variables. Under the optimum condition for the production of rice husk activated
carbon developed, characterization of the rice husk activated carbon was carried out
and column adsorption experiment was conducted in two modes: Rapid Small Scale
Column Test (RSSCT) and Large Scale Column Test (LSCT) using process wastewater
collected from Kaduna refinery and Samaru stream water. RSSCT was utilized to study
the effect of process variables: flow rate and bed depth and the experimental data
obtained were fitted into column models (BDST, Thomas and Yoon-Nelson), while the
LSCT was employed to obtain the peak adsorption performance. For the batch
adsorption, process variables were observed to have significant effect on the
performance of the adsorption process. Adsorption capacity and removal efficiency of
2.4 mg/g and 96 % were attained and equilibrium was found to occur between 10-20
vii
minutes. Adsorption capacity and removal efficiency were also observed to be
maximum at pH=4 and better favoured at lower temperatures. The adsorption process
was found to be inconsistent with the assumption of Langmuir monolayer but
conformed to Freudlinch assumption of multilayer and physical adsorption. The data
followed pseudo-second order kinetic model and intra-particle diffusion was not the
only rate-limiting step. The adsorption process was also found to be exothermic. The
model equations developed have correlation coefficient (R
2
) values of 0.9979 and
0.9981 for removal efficiency and adsorption capacity respectively. Optimization
revealed that the optimum temperature for the production of rice husk activated carbon
is 441.46 oC. The models were experimentally validated under optimum condition.
Phosphoric acid modification of rice husk was also observed to enhance the surface
area from 12.47 to 102.4 m
2
/g and micropores from 2.4 to 1.82 nm. This was confirmed
from the SEM micrographs while FTIR analysis revealed the existence of oxy- and
phosphorous-oxy-containing functional groups. RSSCT shows that performance of the
column adsorption was significantly affected by bed depth and flow rate. The column
experimental data fitted well to Thomas and Yoon-Nelson models. LSCT shows that
the column experiment attained relatively high adsorption capacity of 55.106 mg/g at
exhaustion point of 0.9; this implies the peak adsorption capacity of the rice husk
activated carbon.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE
STUDIES, AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD
OF THE DEGREE OF
DOCTOR OF PHILOSOPHY IN ENVIRONMENTAL ENGINEERING
DEPARTMENT OF WATER RESOURCES AND ENVIRONMENTAL
ENGINEERING
FACULTY OF ENGINEERING
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
Keywords
PERFORMANCE EVALUATION,, TREATED RICE HUSK ACTIVATED CARBON,, WATER TREATMENT,, REMOVAL OF PHENOL