Simple adsorptive removal of Crystal violet, a triarylmethane dye, from synthetic wastewater using Fe (III) treated pine needle biochar

Abstract

Abstract Untreated and Fe (III) treated, cost effective pine needle biochar (PNB) wereevaluatedat different pH forremoval of toxic crystal violet (CV) dye from synthetic wastewaters. Adsorption kinetics followed pseudo-first order kineticsinvolving intra-particle diffusion process. Theadsorption rate constant increased with Fe-treatment of PNB especially at pH 7.0.Adsorption data of CV fitted well to Freundlich adsorption isotherms and both adsorption capacity(ln K) and order of adsorption (1/n) of CV nearly doubled with Fe (III)treatment of PNB at pH 7.0. Desorption of adsorbed CV from both untreatedand Fe(III) treatedPNB could be eplained satisfactorily by third degree polynomial equations. Increase in ionic strength and rise in temperature enhanced dye adsorption onto untreated and Fe(III)treated PNB. Adsorption of CV was an endothermic spontaneous reaction with the increase in entropy of the system. FTIR spectra revealed that C = O of carboxylic acid aryls,C = O and C-O-C inlignin residues of PNB reacted with Fe (III)besides the formation of some iron oxyhydroxide minerals.The changes in FTIR confirmed the possible bonding of positively charged moiety of CV onto untreated and Fe treatedPNB. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) revealed the porous surfaces of PNB with the clear accumulation of Fe (III) after treatment and deposition of CV dye on surfaces and pores of PNB. Iron (III) treatedPNBat pH 7.0 can serve as anecofriendly adsorbent for efficient removal of CV dye from wastewaters.