Removal of Brilliant Green and Crystal violet from Mono- and Bi-component Aqueous Solutions Using NaOH-modified Walnut Shell

In the present work, the simultaneous determination of Brilliant green (BG) and Crystal violet (CV) dyes with overlapped absorption spectra in binary mixture solution was carreid out using the partial least squares (PLS) and direct ortogonal signal correction-partial least squares (DOSC-PLS) methods. The results obtained indicate that applying DOSC on the calibration and prediction data for each dye leads to the significantly minimized error prediction. Walnut shell, as an abundant lignocellulosic agricultural waste, was modified using NaOH, and subsequently characterized by the Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and BET techniques. The potential application of the prepared adsorbent for the removal of the cited dyes was investigated. The effects of the experimental parameters such as the initial pH, adsorbent dosage, initial dye concentration, and contact time on the adsorption efficiency in the single solutions and their binary mixture were also studied. The optimum experimental conditions were found to be 0.8 g l-1 of the adsorbent at room temperature, pH 7.0, and a contact time of 13 min. These advantages fascilitate the dye removal. The analysis data shows that the Langmuire isotherm can satisfactorily explain the equilibrium data. The maximum adsorption capacity (qm) for BG and CV in their single solutions was found to be 146.40 and 123.2 mg g-1, respectively, whereas these values for their binary mixture were 79.07 and 96.01 mg g-1, respectively. The exhausted NMWNS was regenerated using a dish-washing liquid and reused for removal of the cited dye species from aqueous solutions.