The clinoptilolite natural zeolites (NZs) posses low herbicide adsorption capacity demanding acid-, alkali-, or salt chemical modifications that enhance its adsorption. However, this may affect the material structure and charge distribution. Alternatively, zeolites may be synthesized at a high cost and time-consuming process. Consequently, new methods, such as the hydrothermal method, for NZ modification needs to be studied. In this sense, a novel surface-modified zeolite (SMZ), using hexadecyltrimethylammonium bromide (CTAB), in acid media was produced by the hydrothermal method and applied for the adsorption of Atrazine (ATZ), Diuron (DIU) and 2,4-D. Commercial NZ and SMZ were characterized by SEM, XRD, TGA, FT-IR, AA spectroscopy, pH_PZC, Zeta potential and N₂-physisorption. The SMZ chosen for the adsorption experiments was the one with the highest modification yield and adsorption capacity obtained from a complete design of experiments (CTAB=0.74 ; D=12 Mesh; HCl=0.1 M; t=6 h and T=205 ºC). The adsorption experiments revealed that the SMZ adsorption capacity for the herbicide 2,4-D (q_max=9.02 mg/g) was greater than that obtained for ATZ (q_max=2.11 mg/g) and DIU (q_max=1.85 mg/g), which was explained by the presence of the hydroxyl group and by geometric characteristics of the 2,4-D. Adsorption models’ fitting showed that the adsorption of 2,4-D onto SMZ were best described by pseudo-second order kinetic (k₂=0.005-0.006 g/mg.min; q_e,exp=7.122-8.614 mg/g) and Langmuir isothermal model (K_L=0.283-0.499 L/mg; q_m=7.167-7.995 mg/g). These results indicate that the hydrothermal method is a viable alternative to enable the use of NZs for the adsorption of emerging contaminants from wastewater. GRAPHICAL ABSTRACT

Moringa oleifera seeds, in particular, have been used for water and wastewater treatment due to their ability to remove many pollutants. Therefore, the present work aims to produce bioadsorbent materials by pyrolysis using biomass from the seed shell of Moringa oleifera to remove the drug Metronidazole present in an aqueous medium. The biochars produced were activated with phosphoric acid (H₃PO₄) and potassium hydroxide (KOH) to compare the material’s modifications and adsorption mechanisms with the biochar in nature (BCM). The biochars were characterized by Point-of-zero charges (pH_pzc), Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The studies showed that the adsorption behavior varied with the pH of the solution. The adsorption study verified that the activated biochars presented better results, so in the kinetic study, the adsorption behavior occurred rapidly in the initial minutes until stabilizing within 3–4 h, better fitting the Elovich model. Isotherm models were tested, where the experimental data were adjusted to the Sips model, with an adsorption capacity of 18 mg g⁻¹ for acid-activated biochar (BCH₃PO₄) and KOH-activated biochar (BCKOH) with 366.49 mg g⁻¹. The results showed that biochars, especially BCKOH, become viable for production because they are a low-cost material and highly effective in removing drugs.