Comparison of effective removal of cationic malachite green dye from waste water with three different adsorbents: date palm, date palm biochar and phosphated biochar

Abstract

ABSTRACT Adsorbents obtained from agricultural wastes attract attention because they are both effective, inexpensive and environmentally friendly. In this study, it was studied on the removal of malachite green (MG) from aqueous solutions by using date palm fronds (DPF), which are agricultural wastes, date biochar (DPC) obtained by pyrolysis and phosphated date biochar with the help of microwave pyrolysis (DPMW) as three different adsorbents. Characterisation of adsorbents was made by FTIR/ATR, SEM, TGA. According to the results of TGA, it was observed that thermal strengths decreased after adsorption. Adsorption studies were carried out at 25°C in isothermal environment at the pH of the natural dye solution. Adsorption data of date palm, biochar and phosphated biochar were evaluated according to Freundlich, Langmuir, Temkin, Dubinin-Radushkevich (D-R), Flory-Huggings (F-H) and Fowler-Frumkin-Guggenheim (FFG) isotherm models. Maximum adsorption capacities (qmax) according to Langmuir isotherm were found as 334 mg/g, 125 mg/g and 32 mg/g for date palm, biochar and phosphated biochar, respectively. The heat of adsorption calculated using the Temkin and Fowler – Frumkin-Guggenheim (FFG) isotherms is exothermic for date palm and biochar, while it is endothermic for phosphated biochar. It was observed that the adsorption mechanism energy E calculated in D-R and the B values calculated in Temkin were compatible and the adsorption was physical. According to these results, the most effective adsorbent for the removal of malachite green from aqueous solutions is biochar, which is the pyrolysis product, while phosphated biochar is not very suitable.