This study integrates molecular dynamics (MD) simulations and density functional theory (DFT) computations to elucidate the unique adsorption characteristics of phenol and para-chlorophenol onto sepiolite by examining structural deformation, electronic properties, and adsorption energetics. The hydroxyl group (-OH) of phenol mainly determines its adsorption process since it has a quite negative Mulliken charge (−0.428) and significant electrophilic reactivity (fi⁺ = 0.090), therefore enabling strong hydrogen bonding with the silanol (-SiOH) groups of sepiolite. By π-π interactions with the electron-rich siloxane (-Si-O-Si-) surfaces, the aromatic carbons in phenol improve stability. The close molecular structure allows minimum deformation energy (E_def = 94.18 kcal/mol), hence optimizing alignment with the sepiolite surface. The much negative adsorption energy (E_ads = −349.26 kcal/mol) of phenol supports its further thermodynamic stability. Conversely, because of its copious chlorine (-Cl) component, para-chlorophenol runs against steric and electrical obstacles. The virtually neutral Mulliken charge (−0.020) limits electrostatic interactions even if the chlorine atom shows great electrophilicity (fi⁺ = 0.278). Chlorine’s electron-withdrawing action lowers the hydroxyl group’s (fi⁺ = 0.077) reactivity, hence lowering hydrogen bonding. Moreover, para-chlorophenol shows strong deformation energy (E_def = 102.33 kcal/mol), which causes poor alignment and less access to high-affinity sites. With less negative than phenol, the adsorption energy for para-chlorophenol (E_ads = −317.53 kcal/mol) indicates its reduced thermodynamic affinity. Although more evident in para-chlorophenol because of the polarizable chlorine atom, van der Waals interactions do not balance its steric hindrance and reduced electrostatic interactions. With a maximum Qmax = 0.78 mmol/g, isotherm models confirm the remarkable adsorption capability of phenol in contrast to Qmax = 0.66 mmol/g for para-chlorophenol. By hydrogen bonding and π-cation interactions, phenol builds a dense and structured adsorption layer, and para-chlorophenol shows a chaotic organization with reduced site use. Supported by computational approaches and experimental validation, the results provide a comprehensive knowledge of adsorption mechanisms and provide a basis for the design of adsorbents catered for particular organic pollutants.

HIGHLIGHTS. Algerian Bentonite used as raw and low cost adsorbent.The maximal adsorbed quantities of cadmium and iron are respectively 76 mg/g and 55 mg/g at hi

The adsorption of phenol onto dried biomass was studied as a function of initial phenol concentration, temperature, and particle sizes. The maximum phenol adsorption yields were obtained at the temperature of 30°C, the equilibrium uptake increased with increasing initial phenol concentration and the best adsorbed amounts were obtained for particle sizes between 0.05 and 0.40 mm for biomass Pleurotus Mutilus. The Freundlich and Langmuir adsorption models have been used for the mathematical description of the adsorption equilibrium. The results show that experimental data fit perfectly the Langmuir model.

The ability of the use of dried activated sludge for removing methylene blue (MB) was investigated. The dye binding capacity of biosorbent was shown as a function of initial dye concentration, initial pH, and temperature at agitation rate 700 rpm. The experimental results indicated that the equilibrium between the dye and the adsorbent in the solution was established within 30 min and the maximum % removal value was found as 96.54% at pH 7.5. The uptake biosorption increased with increasing initial MB concentration. The maximum MB adsorption capacities were obtained at the temperature of 30°C. The equilibrium data fitted very well to the both Freundlich and Redlich–Peterson adsorption models with high correlation coefficient (R² > 0.99). The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data, consequently; the results showed that the dyes uptake processes followed the pseudo-second-order rate expression. So, it can be concluded that dried activated sludge could be a potential low-cost biosorbent for the MB removal from aqueous solutions.