Adsorption of phenol over bio-based silica/calcium carbonate (CS-SiO₂/CaCO₃) nanocomposite synthesized from waste eggshells and rice husks

A bio-based Silica/Calcium Carbonate (CS–SiO 2 /CaCO 3 ) nanocomposite was synthesized in this study using waste eggshells (ES) and rice husks (RH). The adsorbents (ESCaCO , RHSiO and, CS-SiO characterized XRD show crystallinity associated with the calcite quartz phase. FTIR of ESCaCO shows CO ?2 group CaCO 3, while spectra RHSiO2 majorly siloxane bonds (Si–O–Si) addition to asymmetric symmetric bending mode SiO . for Chitosan (CS) peaks corresponding C=O vibration amides, C–N stretching, C–O stretching. CS–SiO pattern 2. FESEM micrograph a near monodispersed spherical morphology, an average size distribution 32.15 ± 6.20 nm. EDX showed representative Ca, C, Si, O. highest removal efficiency phenol over observed compared other adsorbents. Adsorbing 84–89% 60–90 min at pH 5.4, dose 0.15 g 20 ml 25 mg/L concentration. result kinetic model adsorption processes be best described by pseudo-second-order. correlation coefficient ( R 0.99 nanocomposite, followed equilibrium data all fitting well Langmuir isotherm model, follow trend > equation Freundlich higher = 0.9912 0.9905) onto maximum capacity q m 14.06 mg/g (10.64 mg/g) (10.33 mg/g). results suggest good monolayer coverage on adsorbent’s surface (Langmuir) heterogeneous surfaces available binding sites (Freundlich).