Application of Biochar for Treating the Water Contaminated with Polar Halogenated Organic Pollutants

Abstract

Application of biochar and ionic liquid-impregnated biochar was successfully tested for removal of nonbiodegradable polar halogenated aromatic contaminants (anti-inflammatory agents diclofenac and flufenamic acid and azo dye Mordant Blue 9) from contaminated aqueous solutions. The time dependence of removal efficiencies and adsorption isotherms were evaluated, and the effect of applied ionic liquids (quaternary ammonium salts) was considered. The determined removal efficiencies of the abovementioned contaminants based on the application of biochar or biochar combined with quaternary ammonium salts were compared with the action of commercially available active carbon and/or published results obtained by the action of additional low-cost sorbents. It was demonstrated that a more laborious two-step technique, based on the initial preparation of impregnated biochar by the action of R 4 NCl with subsequent application of this modified sorbent, is much less effective than simple mixing of biochar with R 4 NCl directly in the treated wastewater solution. Experiments dealing with log P OW determination were performed using the same apparatus. An aqueous solution containing 1 mmol of studied contaminant was introduced to the round-bottomed flask (in case of studying log P OW of ion pairs, 1 mmol of R 4 NCl per mmol of -COONa or -SO 3 Na group bound in contaminant was added subsequently); the total volume of aqueous phase was adjusted to 100 mL with water saturated with octan-1-ol, and the mixture was fulfilled using 100 mL of octan-1-ol. The prepared two-phase mixture was agitated at 400 rpm overnight, and the immiscible phases were separated in a separatory funnel, and a concentration of the tested chlorinated aromatic acid sodium salt or their ion pair with R 4 N + in the aqueous phase was analyzed using VIS spectroscopy in the case of MB9 and R 4 N.MB9. In the case of NaDCF or R 4 N.DCF, the concentration in the aqueous phase was analyzed using voltammetric determination.