Fast adsorption of BPA with high capacity based on π-π electron donoracceptor and hydrophobicity mechanism using an in-situ sp2 C dominant N-doped carbon

In this study, a high capacity (q(m)= 1351 mg g(-1)) with fast adsorption process (t < 5 min) towards bisphenol A (BPA) from water was achieved by an in-situ sp(2) C dominant N-doped carbon (polydopamine-carbon, PDA-C). The adsorption mechanism facilitating to the superior removal performance of PDA-C was systematically investigated by relationship study (adsorption capacity VS physiochemical property) and theoretical calculation. It could be concluded that the dominant sp(2) C (I-D/I-G= 0.92-1.02) and N-heteroatom (2.26-5.09 at. %) in PDA-C contributed to enhancing the adsorptive interactions of p-p electron donor-acceptor and hydrophobic effect between the PDA-C and BPA, thus realized a similar to 1.8 times enhancement of q(m) in comparison with the conventional carbon (PRF-C). Calculated adsorption energy from the density functional theory (DFT) further demonstrated that the adsorption potential of N-doped carbon towards BPA increased linearly with increasing doping of N-heteroatom, especially for the pyridinic N which determined the hydrophobic effect of carbon. This finding firstly points out the dominant strengthening mechanism of N-heteroatom for carbonaceous adsorbent. The synthesized PDA-C showed a promising environmental application potential as revealed from the stable BPA adsorption efficiency in the interferences (H+/ OH-, NaCl and HA), dynamic adsorption operation and multiple cycling test.