Electronic Supplementary Material (ESI) for Environmental Science: Water Research & Technology. This journal is © The Royal Society of Chemistry 2020

Adsorption performance and mechanism of from aqueous solution on porous boron-nitride-carbon nanosheets

Gang Wanga,b,*, Yunqi Zhangb, Shiyong Wanga,b, Yuwei Wanga, Haoran Songa, Sihao

Lva， Changping Lia,*

a School of Environment and Civil Engineering, Research Center for Eco-

Environmental Engineering, Dongguan University of Technology, Dongguan

523106, Guangdong, China

b School of Chemical Engineering, Dalian University of Technology, Dalian

116024, Liaoning, China

1 1. Adsorption kinetics Adsorption kinetics mainly studies the factors that affect the adsorption rate during the adsorption and separation of ions, such as time, concentration, temperature and so on. Adsorption kinetics model is the main content of adsorption kinetics, which can accurately reflect the adsorption rate constant and adsorption mechanism between adsorbent and adsorbent. Adsorption kinetics can be divided into two types: quasi-first order kinetic model and quasi-second order kinetic model. The main factors of adsorption kinetics are adsorption volume, concentration and time. Adsorption amount is the mass of adsorbent contained in unit mass. The equation for the relationship between the three is as follows: the adsorption capacity at equilibrium -1 -1 Qe (mg g ) and t (min), the adsorption capacity of the antibiotics adsorbed Qt (mg g ) can be calculated by formulas 1 and 2:

(C0  Ce)V Qe  M (1)

(C0  Ct)V Qt  M (2)

-1 Where, C0 (mg·L ) is the initial concentration of the solution in the -1 adsorption process, and Ce (mg·L ) is the concentration of the antibiotic solution when the adsorption reaches equilibrium in the adsorption process. V (L) is the total volume of the solution in the adsorption process; M (g) is the mass of the adsorbent in the adsorption process.

1.1 Quasi-first-order dynamics The standard first-order kinetic model is the equation of the ideal state, but there is no ideal condition in reality. Therefore, the quasi-first-order kinetic equation is a new model after modification, which can be equivalent to the dynamics of the first- order reaction, which is called quasi-first-order dynamics. Only one factor (solution concentration) was found to determine the adsorption reaction rate, while other factors had no effect on the reaction rate. The quasi-first-order dynamic equation is shown in formula 3:

ln(Qe  Qt)  lnQe  K1t (3) -1 Where, Qt and Qe (mg·g ) are the adsorption quantities at time t (min) and -1 equilibrium, respectively, and K1 (min ) are the quasi-first-order kinetic adsorption rate constants. 1.2 Quasi-secondary dynamics Similarly, the quasi-second order kinetic equation is a modified new model that can be equivalent to the dynamics of the second order reaction, which is called quasi- 2 second order dynamics. Among many factors, there are many factors that affect the process of adsorption reaction, such as solution concentration, temperature, pH, ionic strength, adsorbent, etc., which all affect the rate of adsorption reaction. The quasi-second-order dynamic equation is shown in formula 4: t 1 1   t Qt Qe (4) 2 K2Qe Where, Qt and Qe (mg·g-1) are the adsorption quantities at time t (min) and equilibrium, respectively, and K2(g·mg-1∙min-1) are the quasi-secondary kinetic adsorption rate constants.

2. Adsorption thermodynamics Adsorption equilibrium isotherm is an effective method to accurately estimate the relationship between adsorption and equilibrium concentration. The Langmuir isotherm model assumes that the adsorbent surface is completely flat and the adsorption energy is the same everywhere. There was no interaction between adsorbate molecules. Adsorption is monolayer, once adsorbed molecules occupy a site, adsorption cannot occur at the site. When the adsorbent surface is saturated with adsorbents, its adsorption capacity reaches the maximum. Freundlich is an empirical formula to describe the relationship between adsorbent concentration on the surface and adsorbent concentration in solution, and is the most important isotherm to describe multi-site adsorption on rough surfaces. Herein, Langmuir and Freundlich adsorption isotherm models were used to analyze equilibrium data. The mathematical equation of Langmuir and Freundlich model is as follows: Ce 1 1   Ce Langmuir Qe QmKL Qm (5) 1 lnQe  ln KF  ln Ce Freundlich n (6) -1 Where, Qm (m g ) is the maximum adsorption amount of antibiotics per unit -1 mass adsorbent, KL (L mg ) and KF are Langmuir and Freundlich constant, respectively, and 1/n is a measure of adsorption strength.

The infinitesimal lattice number RL is called the separation factor and is the basic parameter of Langmuir isotherm, which can be calculated by the following formula: 푅 = 1/(1 + 퐾 ) × 퐶 퐿 퐿 푖 (7) -1 Where, Ci (mg L ) is the initial concentration of the antibiotic solution.

3 Fig. S1 The thickness of BCN(a), MBCN(b) analyzed by atomic force microscopy.

Fig. S2 B, N, C and O element distributions of MBCN (a) and BCN (b); O1s XPS deconvoluted peaks of MBCN c) and BCN (d).

4 Fig. S3 TGA of BCN, MBCN and AC

Fig.S4 XRD patterns of BCN (a) and MBCN (b) before and after 2 cycles; SEM images of BCN (c, d) and MBCN (e, f) before and after 2 cycles. Inset: EDS analysis of BCN and MBCN before and after 2 cycles. 5 Table S1 The characterization results of BCN, MBCN and AC

BET Vtotal V Daverage Sample micro (m2/g) (cm3/g) (nm) (cm3/g) BCN 1098 0.534 0.443 2.4

MBCN 539 0.243 0.001 5.4 AC 1509 1.124 0.874 2.1

Table S2 The physics-chemistry properties of CAP and ROX (CAP) Roxithromycin (ROX) XlogP[1] 0.96 3.1 [2] pKa 5.5 9.2 Solvability 2.5 mg/mL 18 µg/mL Molecule Dimension[3,4 ] 17.5×7.3×22.1 Å 11.7×16.8×24.1 Å Molecule structure

Table S3 Summary of antibiotics adsorption capacity of several adsorbents in recent reports.

Materials Antibiotics Specific surface Qe Temp./pH Ref. area (m2g-1) (mg g-1) Porous carbons prepared Chloramphenicol 2337.06 506.1 298k/7 5 from potassium citrate Bamboo charcoal Chloramphenicol 67.80 ≈5.8 303K/7 6 Ordered mesoporous carbon originated from Chloramphenicol 1026 210 303K/7 7 polyethylene glycol 400 Core–shell imprinted Chloramphenicol / ≈39.01 318K/7 8 nanospheres Zeolite by using carbothermal reduction Roxithromycin 138.4 53.65 303K/9 9 electrolytic manganese residue

6 MnO2 and ferrihydrite Roxithromycin 190 and 327 ≈0.95 293K/6.5 10 Ordered mesoporous 233.37 and carbon and bamboo-based Ciprofloxaci 767 and 1746 298K/6 11 362.94 carbon Hexagonal boron nitride 871.46 92.15 298K 12 bundles BCN Chloramphenicol 1098 546.15 298K/7 this work MBCN Roxithromycin 539 575.68 298K/7 this work

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