Immobilization Of NZVI In Polydopamine Surface-modified Biochar For Adsorption And Degradation Of Tetracycline In Aqueous Solution

Tetracycline(TC)is one of the broad-spectrum antibiotics used in medical,animal husbandry and aquaculture industries.And TC may pose potential risks to drinking water safety and human health.The general techniques were used for removal of TC in wastewater,such as adsorption,photo degradation,reduction,and biological methods.Nano zero-valent iron(NZVI)has received great concerns in groundwater treatment and soil remediation due to its large specific surface area,high reactivity,and low cost for the removal of a various of pollutants,such as heavy metals,nitrobenzene,chlorinated organic compounds(COCs)and antibiotics.However,there are some problems that inhibit the application of NZVI technology,such as the agglomeration of NZVI particles and the oxidation of NZVI particles.In order to control the particles agglomeration,various solid supports have been applied to stabilize nanoparticles.Compared with other materials,BC has some distinct advantages,such as higher specific surface area,more stable structures capacity,greater adsorb ability and environment friendliness.In this study,polydopamine/NZVI@biochar composite(PDA/NZVI@BC)composites were innovatively synthesized.The purpose of this work was to improve the dispersion and activity of NZVI by using the new PDA/NZVI@BC composites prepared.In this study,biochar was synthesized by pyrolysis of rice husks in a tube furnace under nitrogen atmosphere.A hydrophilic polymer layer is then formed on the surface of the BC by dopamine self-polymerization,and NZVI is loaded on the surface of the PDA-modified BC by a liquid phase reduction method.In this process,BC acts as a mesoporous matrix,and PDA is an effective modifier that significantly increases the interfacial interaction between NZVI and BC.At the same time,the liquid phase reduction method can well control the particle size of NZVI.Polydopamine/NZVI@biochar composite(PDA/NZVI@BC)with high removal efficiency of tetracycline(TC)in aqueous solutions was successfully synthesized.The resultant composite demonstrated high reactivity,excellent stability and reusability over the reaction course.Such excellent performance can be attributed to the presence of the huge surface area on biochar(BC),which could enhance NZVI dispersion and prolong its longevity.Polydopamine(PDA)is capable to enhance the connection between BC and NZVI due to its hydroxyl groups.Being modified by PDA,the hydrophilicity of biochar was imporved.Among BC,pristine NZVI and PDA/NZVI@BC,PDA/NZVI@BC exhibited the highest activity for removal of TC.PDA/NZVI@BC can remove 98.28% of tetracycline from the solution within one hour.Compared to NZVI iron alone,the removal efficiency increased by 2.43 times.Different important factors impacting on TC removal(including mass ratio of NZVI to BC,initial concentration,pH value and solution temperature)were investigated as well.Obtaining acidic pH,increasing iron loading and temperature and reducing initial pollutant concentration will promote the increase of reaction rate.The reaction kinetics of the removal of tetracycline from PDA/NZVI@BC composites was investigated and described by the two-parameter pseudo-first order decay model.Overall,this study provides a promising alternative material and environmental pollution management option for antibiotic wastewater treatment.