Abstract
The textural properties and surface chemistry of phosphoric acid-modified biochars (PABCs) prepared at different pyrolysis temperatures (500–700 °C) were studied based on the results obtained from XRD, SEM, BET, FT-IR, Raman, XPS and elements analyses. PABCs prepared at higher temperatures tended to possess a bigger proportion of microporous structure. The adsorption capacity and initial rate of PABCs for sulfadiazine (SDZ) were notably improved to 139.2 mg/g and 9.66 mg/(g min) as calculated from the Langmuir model. The adsorption equilibrium time was only one quarter of that without modification. The H3PO4 modification was advantageous to produce phosphate and break functional groups to form disordered carbon structure abundant of micropores. The enhancement in the adsorption of SDZ was due to the confinement effect of hydrophobic cavities from the mircoporous structure and the π–π electron–donor–acceptor interaction. Specially, PABCs exhibited stable adsorption capacities at a wide pH range (3.0–9.0) or relatively high concentrations of coexisting ions.
Highlights
Antibiotics are one class of the most prevalent contaminants, which have been widely used in the pharmaceutical, medical and aquacultural industries (Martucci et al 2014; Zheng et al 2013)
It was obvious that roughly porous structures were revealed on the surface of phosphoric acid-modified biochars (PABCs) after the modification by H3PO4
As depicted in the XRD pattern (Fig. 2a), two obvious broad peaks were discovered at 2θ = 24.2° and 43.4° for PABCs prepared at various pyrolysis temperatures
Summary
Antibiotics are one class of the most prevalent contaminants, which have been widely used in the pharmaceutical, medical and aquacultural industries (Martucci et al 2014; Zheng et al 2013). Sulfonamides (SAs) have a high detection rate in the sewage, water, soil, surface water all over the world because of their large amount of application (Kummerer 2002; Nakata et al 2005; Yan et al 2018) They would induce the generation of drug-resistant bacteria (Bai et al 2014; Davies and Davies 2010; Kim et al 2014), and cause hypoimmunity and dysbacteriosis after entering. Many effective technologies, such as chemical remediation, advanced oxidation, photocatalysis and adsorption have been developed and applied to remove antibiotics (Zessel et al 2014) Among these approaches, adsorption has become one of the most widely accepted technologies due to its economy, feasibility and environmental–friendliness (Gao et al 2012; Hu et al 2020; Kim et al 2020; Ling et al 2016; Xiao et al 2018). The solid residues (coffee grounds, denoted as CGs) containing 40% lignin (Jeguirim et al 2014) are easy to polycondensate to form a polycyclic aromatic hydrocarbon structure, and are believed to be the potential to exhibit a higher fixed carbon content under hyperthermal conditions (Ma et al 2015)
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