## 1 Introduction
Also, the removal efficiency of zeolites depends on the physiochemical and structural properties of zeolites and the type of pollutants, such as mono- and divalent cations, mono- and divalent anions, and organic and inorganic pollutants [17]. However, due to the abundant presence of some impurities, the porous surface of natural zeolite can become clogged, which ultimately decreases its specific surface area and reduces its efficiency in removing heavy metals and other pollutants from the environment. Many kinds of techniques have been employed to improve natural zeolite performance for environmental remediation by enhancing its surface porosity and specific surface area; however, the efficiency of each technique is limited to the zeolite's structural stability [18]. The modification of natural zeolites with surfactants, metal oxides, single or combined thermal treatment, and reaction with chemicals (acid, base, and inorganic salts) are commonly practiced techniques to increase performance in environmental remediation [19]. [PERSON] et al. [20] found enhanced surface area and surface porosity after pretreating natural zeolites with acid and base compounds, which ultimately enhanced their performance for heavy metal stabilization. In addition to chemical modification, physical/mechanical modification of natural zeolites to nanoparticle size exhibits great potential in immobilizing heavy metals in soil. Converting zeolite amendments to nanosize particles enhances specific surface area and improves pore size and pore volume, which ultimately results in more available active sites to stabilize and adsorb heavy metals [21; 22]. [PERSON] et al. [23] reported that application of a 5% microsized zeolite amendment reduced soil Cd contents by 22%, while reducing the zeolite size to nanoscale (NZ) improved its efficiency exponentially by mitigating Cd and Cu concentration in soil by 20 folds [24; 25]. In another study, [PERSON] and [PERSON] [26] reported amplification of surface area and higher adsorption capacity of NZ sediments by mechanically modifying their size to nanoscale. Likewise, [PERSON] et al. [27] conducted an incubation study to assess the potential impact of NZ and its derivative layered double hydroxide (LDH)-modified NZ in mitigating the availability of Cd and Pb in contaminated soil and found a 50% reduction of extractable Cd concentration from 22.17 mg kg\({}^{-1}\) to 11.03 mg kg\({}^{-1}\) using NZ, and from 22.17 mg kg\({}^{-1}\) to 6.47 mg kg\({}^{-1}\) using LDH-NZ, whereas Pb extractable concentration was dropped from 23.28 mg kg\({}^{-1}\) to 14.12 mg kg\({}^{-1}\) in NZ-treated soil and from 23.28 mg kg\({}^{-1}\) to 9.47 mg kg\({}^{-1}\) in LDH-NZ-treated soil. To the best of our knowledge, most of the research work on zeolite application has focused on the utilization of natural zeolite sediments to remove heavy metals from terrestrial and aqueous systems. In contrast, limited research has focused on the chemical and physical modification of zeolite and their impacts on the stabilization of heavy metals from contaminated soil. Therefore, the objective of this research was to evaluate the effect of chemical modification of locally collected zeolite sediments with a combination of techniques using acid, base, and LDH compounds and the physical separation of zeolite sediments to micro- and nanoparticle sizes on the physiochemical and surface characteristics of zeolite sediments and their efficiency in the stabilization of Cd and Pb from contaminated mining soil.