Abstract
In this work, adsorption of carbaryl from aqueous solution on Pistia stratiotes biomass was investigated. The effects of operating parameters such as initial concentration, pH, adsorbent dose and contact time on the adsorption of carbaryl were analyzed using response surface methodology. The proposed quadratic model for central composite design fitted very well to the experimental data that it could be used to navigate the design space according to analysis of variance results. Response surface plots were used to determine the interaction effects of main factors and optimum conditions of the process. The optimum adsorption conditions were found to be initial carbaryl concentration = 15.57 mg L−1, pH 2.01, adsorbent dose = 0.72 g and contact time = 30 min. The Langmuir, Freundlich and Temkin isotherm models were applied to the equilibrium data. The maximum biosorption capacity of P. stratiotes biomass for carbaryl was found to be 3.1 mg g−1. The pseudo-second-order kinetic model described the carbaryl biosorption process with a good fitting.
Highlights
In this work, adsorption of carbaryl from aqueous solution on Pistia stratiotes biomass was investigated
There are several procedures available for pesticides removal from water which includes photocatalytic degradation (Ugurlu and Karaoglu 2011; Gong et al 2011), ultrasound combined with photo-Fenton treatment (Katsumata et al 2011), advanced oxidation processes (Zhou et al 2011), aerobic degradation (Rajashekara Murthy and Manonmani 2007), electrodialysis membranes (Banasiak et al 2011), ozonation (Maldonado et al 2006) and adsorption (Al-Muhtaseb et al 2011)
In the first step of the study, the effects of operating variables such as initial carbaryl concentration, pH, adsorbent dose and contact time on carbaryl capacity of P. stratiotes biomass were investigated using response surface methodology (RSM) according to central composite design (CCD)
Summary
A fresh 0.03 % (w v-1) methanolic solution of 4-nitrobenzene diazonium fluoborate (Sigma Aldrich) A.R. 5 mL of 0.5(N) NaOH solution was added to 5 mL of aliquot taken in a 20 mL volumetric flask followed by the addition of 5 mL of 0.03 % (w v-1) methanolic solution of p-nitrobenzene diazonium fluoborate. The influence of pH (2.0–8.0), initial carbaryl concentration (5, 10, 15, 20 mg L-1), contact time (1, 5, 10, 20, 30, 60 min) and adsorbent dose (0.05, 0.1, 0.5, 0.8 g per 100 ml) were evaluated during the present study. Samples were collected from the flasks at predetermined time intervals for analyzing the residual carbaryl concentration in the solution. The amount of carbaryl ions adsorbed in milligram per gram was determined by using the following mass balance equation: qe 1⁄4. The control experiments were performed without the addition of adsorbent which confirmed that the biosorption of carbaryl on the walls of flasks were negligible. Y 1⁄4 b0 þ bixi þ bijxixj þ biix2ii þ e ð4Þ i1⁄41 i1⁄41 j1⁄41 i1⁄41 where Y is the response variable; b0 is the intercept; bi, bij and bii are coefficients of the linear effect, double interactions; xi, xj are the independent variables or factors and e is the error (Table 2)
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