Competitive adsorption of cadmium and aluminum onto fresh and oxidized biochars during aging processes

Abstract

Purpose Fresh biochar was shown to effectively reduce concentrations of heavy metal in soil, but the influences of the aging processes of biochar and competitions from other elements are warranted to precisely evaluate the long-term effect of biochar. This work investigated the effects of water washing, oxidation, and coexistence of aluminum (Al) on cadmium (Cd) adsorption by biochars and oxidized biochars. Materials and methods The Cd adsorption and the competitive adsorption of Cd and Al to rice straw-derived biochars, before and after oxidation by HNO 3 /H 2 SO 4 , were investigated. Meanwhile, the structural characteristics and surface charges of primary and oxidized biochars, with and without Cd loading, were analyzed by scanning electron microscopy, fourier-transform infrared spectroscopy, and zeta potential. Results and discussion The adsorption of Cd onto fresh biochars was dominated by surface complexation of oxygencontaining functional groups via esterification reactions, which was regulated by solution pH. Oxidization (aging) introduced carboxylic functional groups to biochar surfaces, which served as additional binding sites for Cd. The Cd binding to biochars was significantly affected by the coexistence of Al via acidification and competition for adsorption sites. Conclusions The biochars exhibited high sorption capacities of Cd in soil, but soil acidification led to a counteractive of biochar's liming effect and a reduction of Cd-binding sites; thus, the long-term effect of biochar for heavy metal immobilization should be paid more attention in acidic soil.

Biochar Modification, Thermal Stability and Toxicity of Products Modification

“…Note to the content of the publication LO Before After CH 3 OH + Improvement of adsorption capacity to tetracycline (Jing et al, 2014) H 2 O 2 + Utilization of the role of -OH radicals (G. FeCl 2 , FeSO 4 , Ni(NO 3 ) 2 + Preparation of magnetic biochar (Safarik et al, 2012) GRAPHITE+ Py-SO 3 + Sorption material for PAU sorption KMnO 4 , HNO 3 + Testing of changes of adsorption capacity Nanoparticles of metals, Fe(NO 3 ) 3 , Ni(NO 3 ) 2 + Introduction of metal nanoparticles into the structure Monomers, oligomers, polymers + Preparation of polymer composite materials (Das et al, 2015) KOH, NaOH + Preparation of a catalyst of alkaline character (Abdul Hamid et al, 2014) HNO 3 , H 2 SO 4 + Improvement of adsorption capacity to Cd and Al ions (Qian et al, 2015) Metal salts (Fe, Pd, Pt, Ni) + Preparation of a catalyst biochar -metal (Shen, 2015) KOH, NaOH + Increase of biochar surface (Gu and Wang, 2013) (Tan et al, 2016) Clays, kaolin, montmorillonite + New material -testing of adsorption kinetics (methylene blue) (Yao et al, 2014) H 2 SO 4 , solution KOH + Improvement of adsorption capacity to tetracycline (P. HNO 3 50 % + Formation of carbonaceous nanoparticles (Manav et al, 2016) CNT (0.01-1%) + Improvement of sorption capacity (Inyang et al, 2014) Lignite + Joint processing -hydrothermal (Z. MnCl 2 . 4H 2 O + Modifi cation of biochar with MnO x Improvement of sorption capacity to As and Pb KMnO 4 + HCl + Preparation of composite Birnessite -Biochar HNO 3 + H 2 SO 4 (1:1) + Na 2 S 2 O 4 + Amidation of biochar (reduction of NO 2 groups to -NH 2 ), increase of sorption capacity to Cu 2+ (Yang and Jiang, 2014) Chitosan + Sorption of heavy metals and biological activity Fe 3 O 4 + Preparation of sorbents in a ball mill -sorption capacity to antibiotics (Shan et al, 2016) Legend: LO -Reference worldwide-used pharmaceutical products, such as isobrufen (Essandoh et al, 2015), tetracycline (Liao et al, 2013), acetaminophenon (Im et al, 2014), aspirin (Essandoh et al, 2015) toxic industrial substances (Chen and Chen, 2009;Wang et al, 2013), explosives (Oh and Seo, 2014;Oh and Seo, 2015) etc.…”

“…This oxidation resulted in a product with good adsorption ability to Cd and Al ions. In the second case (Qian et al, 2015) the oxidation was performed with 50 % nitric acid at 60 °C and the reaction time was 5 hours. Equally as in our work, FT-IR analysis was used for basic identifi cation of functional groups.…”

“…A medium strong vibration with the maximum at 3420 cm -1 was assigned to the bond vibration -OH. In case of the second experiment (Qian et al, 2015) the authors believed that a part of biochar formed nanoparticles soluble in water. This solubility was possible due to the presence of the groups -COOH (1717 cm -1 ) and -OH.…”

Effect of aging process on adsorption of diethyl phthalate in soils amended with bamboo biochar

“…Also, aging processes may introduce functional groups (i.e. carboxylic) to biochar surfaces, thereby impacting its adsorption properties (Qian et al, 2015).…”

Co-remediation of Pb Contaminated Soils by Heat Modified Sawdust and Festuca arundinacea

“…Research on recycling and reuse of biomass wastes is a very important strategy to improve the utilization of bio-energy resources 5 . Heat modified biomass materials can effectively stabilize heavy metals in soil, thereby alleviating the heavy metal toxicity in the environment 6 . X.D.…”