modeling and optimizing lead ions adsorption by walnut shell modified by sepiolite from aqueous solution by response surface methodology

Activated carbon from the walnut shell modified by sepiolite (ac/sep) composite was synthesized and applied for the adsorption of toxic lead (pb(ii)) ions from industrial effluents.  ac/sep composite was characterized by fourier transform infrared (ft-ir) spectrometer, field emission scanning electron microscopy (fesem), brunauer–emmett–teller (bet), and x-ray diffraction (xrd) analyses. effects of ph, amount of adsorbent, lead initial concentration, and contact time on removal percentage were studied by central composite design  (ccd). the optimal condition for maximum lead removal by ac/sep adsorbent (99.07%) was as follows: ph= 5.00, adsorbent amount: 0.05 g, initial concentration 20.00 mg/l, and contact time: 25.00 min in 10 ml of pollutant volume. also, the adsorption kinetics, thermodynamics, and isotherms were determined. adsorption isotherms (qmax: 269.67 mg/g) and kinetics showed that the sorption process was better modeled by the langmuir and pseudo-second-order equation.