Abstract
Properties of raw bentonite clay of Afuze in Edo state which are abundant and cheap bentonite mineral in Nigeria as adsorbents for the removal of atrazine in aqueous solution were investigated. The bentonite clay-types were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrophotometry and X-ray diffraction (XRD). Batch adsorption experiments were carried out to determine the equilibrium characteristics, thermodynamics and kinetics of the sorption processes. The data obtained were subjected to Langmuir, Freundlich and Temkin isotherm equations, while pseudo-first-order, pseudo-second-order rate equations, intra-particle diffusion and Elovich models were considered for kinetics and mechanism. The results showed that the adsorption processes were described by different isotherm models; they were all spontaneous (∆G ranges from − 938.34 to − 6263.58 kJ/mol) and exothermic (range of ∆H is − 252.73 to − 1057.08 kJ/mol), and with decreased randomness, ∆S (− 3.110 to − 0.581 J.mol/K). Pseudo-second-order kinetics model gave the better fit for all the sorption processes which implies physisorption process as the rate limiting step. Thus, bentonite clay-types can be used to adsorb atrazine.
Highlights
Frequent usage of herbicides at the home, farm land, school field, etc., and discharge of its wastewater from the producing industries into surface water bodies have become endangered to our ecosystem
The sharp bands at 3696.17 cm−1 and 3626.39 cm−1 are attributed to the N–H stretching for the unmodified (pretreated) bentonite clay type (UBC) and 2 M sulphuric acid modified bentonite clay (2-ABC) types as it is the same as the peaks at 3697 and 3620 cm−1 reported by Georges-IVO, (2005)
The peaks at 3436.41 cm−1 in the 2-ABC sample and 3430.21 cm−1 in the UBC are assigned to OH stretching which is close to 3426 cm−1 and 3420 cm−1 reported by Isci et al (2006) and Aroke et al (2013)
Summary
Frequent usage of herbicides (i.e. atrazine) at the home, farm land, school field, etc., and discharge of its wastewater from the producing industries into surface water bodies have become endangered to our ecosystem (i.e. aquatic organism and human). Humans and living organisms can suffer mutagenesis and carcinogenesis as a result of atrazine contamination (EPA 1990). It has been banned in most European countries, it is still one of the most widely used herbicides in the USA and registered in more than 70 countries worldwide (Kauffmann et al 2000). Atrazine is a probable human carcinogen, and its current maximum contaminant level in drinking water established by the environmental protection agency is 3.0 μg/L
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