Research Article: Highly efficient nickel (II) removal by sewage sludge biochar supported α-Fe2O3 and α-FeOOH: Sorption characteristics and mechanisms

Date Published: June 12, 2019

Publisher: Public Library of Science

Author(s): Lie Yang, Liuyang He, Jianming Xue, Li Wu, Yongfei Ma, Hong Li, Pai Peng, Ming Li, Zulin Zhang, Jorge Paz-Ferreiro.

http://doi.org/10.1371/journal.pone.0218114

Abstract

A novel approach was employed to load α-Fe2O3 and α-FeOOH onto sewage sludge biochar (SBC) with the purpose of efficient nickel (Ni) removal. A high Ni(II) adsorption capacity of 35.50 mg·g-1 in 100 ppm Ni(II) solution with 10 mg modified sewage sludge biochar (MSBC) was achieved. The adsorption kinetic and isotherm were fitted well by the pseudo-second-order model and the Langmuir model, respectively. The optimal pH was found around a neutral pH of 7. The adsorption mechanisms of Ni(II) onto MSBC were described as the synergistic effects of electrostatic attraction, ion exchange, inner-sphere complexation and co-precipitation. The initial rapid adsorption phenomenon could be attributed to electrostatic attraction and ion exchange, and then inner-sphere complexation and co-precipitation acted as a crucial role in the following step. The remarkable performance of MSBC provides an effective waste utilization approach to simultaneous sewage sludge recycle and Ni removal from aqueous solution.

Partial Text

Nickel (II) ion (Ni (II)), a toxic heavy metal ion, is discharged into natural waters mainly from various chemical industries, including textile dyeing, electroplating, and metal finishing [1]. Once the concentration of Ni(II) increases to a limit in the water bodies, there is a potential threat to food security and human health. An investigation was conducted in eastern Taiwan to evaluate the health risks of Ni in rice, and much higher Ni concentrations were observed in rice grain from Ni contaminated fields [2]. Furthermore, the incidence of oral cancer was found correlated positively with levels of Ni in farm soils based on a compulsory national health insurance program in Taiwan [3]. Soil contamination with Ni was frequently caused by discharge of Ni wastewater without appropriate treatment. Therefore, effective and economical technologies for the Ni removal in wastewater are urgently needed.

Modified sewage sludge biochar (MSBC) was technically produced by distributing both α-Fe2O3 and α-FeOOH particles onto the surface of SBC. The maximum Ni adsorption capacity of MSBC reached 35.50 mg·g-1. The adsorption process could be fitted by the pseudo-second-order model and adsorption isotherm was well described by the Langmuir model. The initial rapid adsorption phenomenon could be attributed to electrostatic attraction and ion exchange, and then inner-sphere complexation and co-precipitation acted as a crucial role in the following step. Although the mechanism of Ni(II) adsorption was believed to be the synergistic effect of physical and chemical adsorptions, the dominant role was proved to be chemical adsorption. The results in this study indicate that MSBC could act as an excellent adsorbent for Ni removal.

 

Source:

http://doi.org/10.1371/journal.pone.0218114