Adsorptive capture of Congo red and Erythromycin pollutants from water by Functionalized ecofriendly chitosan and nanobiochar with silica gel

Abstract

Both chitosan and biochar are known as biodegradable and ecofriendly materials with different functional groups that enable strong binding with various pollutants. Dyes and pharmaceuticals in wastewater are categorized as serious hazardous pollutants due to their nonbiodegradability and therefore, must be removed before discharge in water resources. In this work, a novel nanobiosorbent was designed and fabricated from three constituents based on the pyrolysis of banana peels to produce nanobiochar (BPNB) as a sustainable material. This was then modified with nanosilica gel via microwave heating to yield (BPNB-SiO2). Chitosan hydrogel (Chit Hgel) as a biodegradable polymer was further crosslinked with BPNB-SiO2 to produce the aimed BPNB-SiO2-Chit Hgel nanobiosorbent with particle size in the range of 22.48–26.23 nm. The effects of initial nanobiosorbent dosage (1–50 mg), initial adsorbate pH (pH 2–12), shaking time (1–45 min), initial pollutant concentration (5–100 mg L− 1), temperature (288–333 K), and interfering salts on the adsorption process of Erythromycin antibiotic (ERM) and Congo red dye (CRD) pollutants were investigated and optimized. The pseudo-second-order model revealed the perfect fit in kinetic investigations of ERM and CRD by BPNB-SiO2-Chit Hgel. The Langmuir model achieved (R2 = 0.997 for ERM and R2 = 0.992 for CRD) as the highest correlation coefficients. Moreover, the adsorption reactions of ERM and CRD onto BPNB-SiO2-Chit Hgel were classified as spontaneous and endothermic. The removal of ERM (92.80–96.50%) and CRD (92.80–95.0%) from tap, sea, and wastewater was successfully established to confirm the capability of the investigated BPNB-SiO2-Chit Hgel nanobiosorbent in removal of these two pollutants from polluted samples.