Efficient Nitrate Adsorption from Groundwater by Biochar-Supported Al-Substituted Goethite

Li Wang, Siyuan Liu, Wendi Xuan, Shaopeng Li and Anlei Wei
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Li Wang: Institute of Architecture, Xianyang Vocational Technical College, Xianyang 712000, China
Siyuan Liu: College of Urban and Environmental Sciences, Northwest University, Xi’an 710127, China
Wendi Xuan: College of Urban and Environmental Sciences, Northwest University, Xi’an 710127, China
Shaopeng Li: College of Urban and Environmental Sciences, Northwest University, Xi’an 710127, China
Anlei Wei: College of Urban and Environmental Sciences, Northwest University, Xi’an 710127, China

Sustainability, 2022, vol. 14, issue 13, 1-24

Abstract: Groundwater nitrate contamination is challenging and requires efficient solutions for nitrate removal. This study aims to investigate nitrate removal using a novel adsorbent, biochar-supported aluminum-substituted goethite (BAG). The results showed that an increase in the initial Al/(Al + Fe) atomic ratio for BAGs from 0 to 20% decreased the specific surface area from 115.2 to 75.7 m 2 /g, but enhanced the surface charge density from 0.0180 to 0.0843 C/m 2 . By comparison, 10% of Al/(Al + Fe) led to the optimal adsorbent for nitrate removal. The adsorbent’s adsorption capacity was effective with a wide pH range (4–8), and decreased with increasing ionic strength. The descending order of nitrate adsorption inhibition by co-existing anions was SO 4 2− , HCO 3 − , PO 4 3− , and Cl − . The adsorption kinetics and isotherms agreed well with the pseudo-first-order equation and Langmuir model, respectively. The theoretical maximum adsorption capacity was 96.1469 mg/g. Thermodynamic analysis showed that the nitrate adsorption was spontaneous and endothermic. After 10-cycle regeneration, the BAG still kept 92.6% of its original adsorption capacity for synthetic nitrate-contaminated groundwater. Moreover, the main adsorption mechanism was attributed to electrostatic attraction due to the enhancement of surface charge density by Al substitution. Accordingly, the BAG adsorbent is a potential solution to remove nitrate from groundwater.

Keywords: biochar; Al substitution; goethite; adsorption; nitrate contamination; groundwater (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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