Characterization and application of biochar-immobilized crude horseradish peroxidase for removal of phenol from water

• A suitability of biochar as a support for HRP immobilization was investigated. • Immobilized enzyme showed the highest activity at temperature 30 °C and pH 7.0. • Utilizing the immobilized enzyme the 90 % of phenol removal was achieved. • Immobilized enzyme significantly reduces the toxicity of the tested water. Biochar (BC) has attracted much attention as an environmentally friendly material for application in wastewater treatment. In this study, a suitability of wood-derived BC as a support for covalent immobilization of horseradish peroxidase (HRP) across glutaraldehide as crosslinker, known for the capability to remove phenol from water, was investigated. The efficiency of the immobilized HRP in removal of phenol (2 mM) from water at different reaction conditions (varying dosages of polyethylene glycol (PEG300) 0−750 mg/L; H 2 O 2 1.5–3.5 mM, as well as reaction time 5−120 min) and the general toxicity of bio-treated water ( Allium cepa test) were measured. All analyzes were performed for free enzyme as well. The immobilized enzyme showed the highest activity at temperature 30 °C and pH 7.0. The greatest efficiency of immobilized enzyme in phenol removing (90 %) was obtained by applying 2.5 mM H 2 O 2 and 1.5 mg/L of PEG300 at pH 7.0 after 2 h of reaction period. After 4 washings, immobilized HRP retained more than 79 % activity with phenol removal of 64 %. Utilizing immobilized enzyme significantly reduces the toxicity of the tested water (80 %), which further suggested that it might be considered as an environmentally acceptable process for wastewater treatment. Possible degradation products remained in treated water were analyzed in water samples by liquid and gas chromatography with mass spectrometry, including also analysis of volatiles by solid phase microextraction technique; different phenol-base compounds were detected.