Potential of Fish Scale Biochar Nanocomposite with ZnO for Effective Sequestration of Cr (VI) from Water: Modeling and Kinetics

Surface and subsurface water resources are polluted with various anthropogenic activities and exert deleterious impact on the ecosystem. In this study, novel fish scale biochar (FSB) and its nanocomposite with zinc oxide nanoparticles (FSB/ZnO) were used to treat chromium (Cr (VI))-contaminated wastewater. Batch scale experiments were designed by varying initial Cr (VI) concentration (25–200 mg L −1 ), interaction time (15–180 min), solution pH (2- 8), and dosage of FSB and FSB/ZnO (1–4 gL −1 ). The surface characteristics of adsorbents were characterized with Fourier-transform infrared (FTIR) analysis and point of zero charge (PZC). Results discovered that maximum Cr removal was achieved with FSB/ZnO (98.70%) followed by FSB (59.40%) at optimum conditions, i.e., pH-4, 50 mg Cr L −1 , and 2 g L −1 adsorbent dosage at equilibrium. The FSB and FSB/ZnO showed maximum adsorption capacity of 48.08 and 90.09 mg g −1 , respectively, which is much higher than many previously explored materials. The isothermal experimental results revealed best fit with Freundlich model ( R 2 = 0.982), while kinetic effects were better simulated with Pseudo 2 nd order (PSO) ( R 2 = 0.999) than other models. It is anticipated that the composite (FSB/ZnO) has greater capacity to treat Cr-containing water in contrast to FSB. Highlights It is the first attempt to use nanocomposite of fish scale biochar with zinc oxide FSB/ZnO showed excellent adsorption potential (90.09 mg/g) for Cr (VI) sequestration Freundlich isothermal and pseudo 2 nd order model well explained the experimental data FSB/ZnO composite proved effective for Cr (VI) sequestration