Abstract
Samples of rock deposit dug out from wells at Alimosho local government in Lagos state, Nigeria were characterized for chemical composition and ultimate utilization. Fourier Transform Infrared Spectroscopy (FTIR), X-Ray diffraction (XRD) and Atomic Absorption Spectroscopy (AAS) were used to identify the rock as a mixed clay rock containing 35.04% Illite, 25.64% Illite plus Quartz, 22.20% Kaolinite and 17.09% Feldspar. This was corroborated by cation determination that showed the rock to be predominantly clayey rock. The mean concentrations of lead and copper in water of the wells in the rock location are 0.004mg/L and 0.05mg/L respectively while cadmium is less than detectable limit. The well water in the area studied is therefore not contaminated by these heavy metals. Heavy metals removal by the mixed clay from polluted underground water was studied using AAS. A general increase of sorption was observed with increase in the adsorbent dosage. 20g of the rock adsorbed a higher percentage of copper (80.23%) than lead and cadmium that were 70.25% and 65.83% respectively. The percentage of heavy metals adsorbed confirms the use of mixed clay minerals as a contaminants removal from the underground polluted water. The rock adsorbed copper readily than cadmium and lead. The maximum amount of lead removed from the contaminated underground water of the defunct battery site across the adsorbent dosage (5g, 10g, 15g and 20g) were 1.20mg/L, 3.19mg/L, 3.69mg/L and 4.09mg/L respectively indicating the effect of increase in adsorbent dosage in remediating the lead contaminated water. This data showed that the rock can be used to remove these heavy metals from contaminated water.
Highlights
There are three main classes of clay rocks: Kaolinite, Micas and Smectite
Several methods have been employed to improve on the cation exchange capacity (CEC) of clay minerals
The total organic carbon (TOC) and total organic matter (TOM) were low suggesting that this characterized rock that does not contain plant residue
Summary
There are three main classes of clay rocks: Kaolinite, Micas (such as Illite) and Smectite (such as Montmorillonite). Of these three classes, Montmorillonite clay has the smallest crystals, largest surface area and large cation exchange capacity (CEC). Several methods have been employed to improve on the cation exchange capacity (CEC) of clay minerals. These include activation, pillaring or intercalation (Hung et al, 1997) and chemical modification of the surface using inorganic complex-forming ions or organic based complex forming ions. The adsorption of metal ions onto mineral substrates is an important process in soil chemistry and in hydrometallurgy and the treatment of industrial wastewaters. Diverse processes such as the uptake of nutrients by plants and the extraction of toxic heavy metal ions from industrial wastewaters depends often on adsorption to soil minerals
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