Adsorption study of heavy metals and natural organic matters (nom) in groundwater using metakaolin
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Date
2019-03-01
Authors
Mohd Sharizal Mohd Sapingi
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Abstract
Groundwater is an increasingly important source of water due to lack of
surface water supply that caused by climates vagaries and declined surface water
quality. However, prior to consumption, it is very essential to recognize the quality
of groundwater to avoid adverse effect to health as the quality differs based on
location. Elevated heavy metals concentrations in groundwater are one of the
common issues due to the anoxic and reductive condition in groundwater. In
addition, high natural organic matter (NOM) content in groundwater decrease the
water aesthetic value and develop disinfection by-product when reacted with
disinfectant. Therefore, the objectives of this study are; 1) To study the quality of
groundwater sampled; 2) to explore capability of metakaolin in order to reduce the
contaminant (iron, manganese, nickel and NOM) concentration in groundwater and
the factors (dosage, agitation rate & contact time) optimization using RSM; and 3) to
determine the suitable isotherm and kinetics behavior for each contaminant. . In
average, the concentration of the contaminant is high with iron (615.4 μg/L),
manganese (444.0 μg/L), nickel (174.6 μg/L) and NOM (as measured in UV254)(1.23
cm-1). The optimum setting (dosage, agitation rate and contact time) was assessed
using RSM where the removal of iron, manganese, nickel and NOM was 82%, 38%,
39% and 22% respectively. High ionic strength and competitive adsorption in a
multi-solute system have been recognized as limiting factors. Isotherm study
signified that the adsorption of all contaminants onto metakaolin fits with the
Freundlich model as the values of 1⁄ > 1 denotes that there is cooperative
adsorption. Langmuir models per contra, does not fit with experimental data due to
unfavorable value of , and . While in kinetic study fits Pseudo-second-order
as a results of lower % Δ value compare with Pseudo-first-order. The percentage
of Δ (pseudo-first-order) for iron, manganese, nickel and NOM are 95%, 97%,
98% and 96% accordingly. While the value of Δ for pseudo-second-order for each
metal are 1% (iron), 28% (manganese), 16% (nickel) and 18% (NOM). These
findings suggesting that there is a surface interaction between contaminants and
adsorbent’s surface which is physisorption.