Removal of crystal violet dye from wastewater using low-cost biosorbent Trifolium repens stem powder

Crystal violet (CV) synthetic dyes are well known in the dyeing industry for their mitotic and mutagenic poisoning. CV dye being a toxic organic dye is responsible for serious health issues as well as environmental damage. In this study, an inexpensive biosorbent (white clover: Trifolium repens) stem powder was tested for the adsorption of CV dye (cationic dye) from an aqueous solution. The batch adsorption measurements were designed to find out the influence of contact time, pH, adsorbent dose, and dye concentration, for dye removal. The operation parameters studied are the contact time (20 to 160 min), initial dye concentration (10-100 mg/L), dose (0.1-1 g), and pH, (1-10). At optimum conditions, maximum percent removal of 92.997% and adsorption capacity value of 1.952 mg/g was achieved at pH 2, adsorbent dose (1 g), and contact time (140 min), and dye concentration (70 ppm). The results suggested that the removal of CV rose with the contact time and adsorbent dose. Langmuir and Freundlich isotherm models were applied to the equilibrium adsorption data, and data were perfectly fitted to Langmuir isotherm model. Pseudo-first-order and pseudo-second-orders were applied to the data, and it was found that the pseudo-second-order kinetic model was best fitted to the experimental data. It was also revealed that the stem powdered of the Trifolium repens plant can be employed as a useful adsorbent to remove cationic CV dye from different water samples (tap, river and distilled). Furthermore, the performance of adsorbent was also evaluated in saline water containing sodium chloride, potassium chloride and manganese chloride salts to check the effect of various ions on the performance of adsorbent and it was observed that the adsorbent showed excellent performance in saline water. Moreover, a comparative study was performed to check the efficiency of different commercial adsorbents (silica gel and active carbon) and to compare their performance with our study. All these experiments revealed that the biosorbent used in this study effectively removes contaminating dyes from industrial wastewater and as well as saline water and thus, can be used for the treatment of wastewater at the commercial level.