In this work, the efficiency of the treated plant Carpobrotus edulis (TPCE) as an effective biosorbent for removing the orange G (OG) and crystal violet (CV) dyes from aqueous solution was investigated. TPCE was characterized by FT-IR, S_s, pH_z and SEM-EDX. The influence of parameters such as bioadsorbent dose, contact time, initial concentration, temperature and pH was tested using Taguchi experimental design (TED) with L₈ orthogonal array (five parameters in two levels). The initial concentration, bioadsorbent dose and contact time are the main parameters for the removal of CV and OG dyes, while the effects of pH and temperature are minimal. The maximum removal efficiency of dyes under optimal operating conditions was 97.93 % and 92.68 %, respectively. which at the optimal conditions of 3 g/L, pH 10, 20 mg/L, 35 °C, 5 min and 15 g/L, pH 4, 20 mg/L, 35 °C, 60 min for CV and OG dyes, respectively. The results of response surface methodology (RSM) and analysis of variance (ANOVA) showed that the initial concentration C_i of CV dye was the most significant factor in the adsorption efficiency with a contribution of 51.56 %. On the other hand, the OG bioadsorbent dose is the most important factor in adsorption efficiency with a percentage contribution of 56.41 %. The Density Functional Tight Binding (DFTB) method shows that dyes strongly bind the adsorbent surface. Monte Carlo and molecular dynamics simulations show significant interactions between dye and adsorbent surface. The reusability of biomaterial indicated that the adsorption performance dropped very slightly up to five cycles.

This paper deals with the valorization of the native Carpobrotus edulis plant (C. edulis) as a bioadsorbent for the removal of toxic dyes such as Rhodamine B (RB) and Congo Red (CR). This plant was further characterized by BET, SEM, EDX, and FT-IR methods. The colorants were applied in a batch adsorption experiment that included measurements of adsorbent ratio, ionic strength, contact time, initial concentration, pH, and temperature. It was observed that for 100 mg/L initial dye concentration, 0.2 g of C. edulis showed maximum adsorption efficiency for RB (> 75%), while 0.4 g for CR (> 70%). For both dyes on the biomaterial tested, ionic strength and pH have no significant impact on the adsorption. Adsorption fits a pseudo-second order kinetic model and Langmuir isotherm. The optimum adsorbed amount of C. edulis was indicated at 56.18 and 19.84 mg/g for RB and CR, respectively. The results of the thermodynamic study show that the adsorption process of the dyes by the biomaterial is spontaneous and exothermic with a decrease in the randomness of the adsorption process. The results of the regeneration indicate that the bioadsorbent was efficiently recycled with 55.80% and 36.26% uptake for RB and CR dyes, respectively, after 3rd cycles of desorption-adsorption. Operational factors were studied using Taguchi’s experimental design. Our experimental results confirm the importance of the influence of initial concentration, adsorbent ratio, and contact time on adsorption with maximum adsorption of RB and CR was found to be 76.06% and 68.18% dye, respectively. Graphical Abstract

The removal of Pb(II) ions from aqueous solution by sorption onto layered double hydroxides (LDHs) is widely documented, yet the reported capacities range from 13 to over 200 mg g⁻¹. The dispersion is usually ascribed to the layer chemistry but cannot be tested because published values come from widely different operating conditions; this work supplies the missing reference member of a single-protocol series. Carbonate-intercalated Mg₂Al–CO₃ was prepared by coprecipitation at constant pH, characterized by XRD, SEM–EDX, N₂ sorption, DSC and pH_PZC, and evaluated as a function of dose, pH, contact time, concentration and temperature. Equilibrium was reached within 60 min, the kinetics were pseudo-first-order, the Redlich–Peterson and Langmuir equations fitted the isotherm best with a monolayer capacity of 59.1 mg g⁻¹, and the uptake was spontaneous and endothermic (ΔH° = 11.1 kJ mol⁻¹). They are then compared with two isostructural phases previously published by our team, Mg₂[FeAl]–CO₃ and Zn₂[FeAl]–CO₃, prepared and tested under strictly identical conditions; no new experiment was performed on these solids, whose values are quoted here for comparison only. Replacing half of the Al(III) by Fe(III) doubles qm to 118.8 mg g⁻¹ and replacing Mg(II) by Zn(II) raises it to 87.9 mg g⁻¹. Normalized to the BET surface area, however, the three capacities converge on 1.55 ± 0.07 mg m⁻²: the layer composition acts on Pb(II) uptake only through the accessible surface area it generates, not through the intrinsic reactivity of the surface. Sorbent design should therefore target textural disorder rather than a particular cation pair.