In this study modified feldspar composite (MFC) adsorbent based on feldspar and Theobroma cacao podas (TCP) was prepared, characterized and utilized for adsorption of Pb (II) and Cr (VI) in aqueous solution. The results showed that the cation exchange capacity of the modified feldspar composite (30.66 ± 0.21 meq/100 g) was 5 times higher than that of raw feldspar (6.42 ± 0.45 meq/100g). More so, the novel biohybrid material, MFC has a surface area of 53.60 ± 0.3 m2/g and particle size of 105.4 ± 0.18. X-ray diffraction peaks revealed that after the modification process, there is only slight shift in the position of some diffraction peaks of feldspar and the composite material suggestive of the retention of the crystalline properties of the feldspar in the novel composite (MFC). Infrared spectroscopy (FTIR) spectra showed that some functional groups present in the two starting materials were also available on the surface of the composite (MFC) indicating that the intercalation of TCP biomass into feldspar surface was successful. Response surface methodology (RSM) via a five-levels central composite design (CCD) was applied for optimization of  metal adsorption onto the adsorbent in 32 experiment runs considering the effect of pH, adsorbent dose, adsorbate concentration and contact time. Optimization results showed that the predicted and experimental values of Pb (14.021, 14.148 mg/g) and Cr (3.428, 3.504 mg/g) were close at the optimum condition of (pH 2, 5, 6; 0.5 g; 100 mg/L; 60-120 min and 3000K). Results of ANOVA analysis revealed the adequacy of the model with the good correlation between R2 values (0.9916-0.9998) and adjusted R2 (0.9919-0.9986) and F value of (≥ 147). Results showed that Pb (II) ions adsorption onto the adsorbents was well fitted to the Langmuir isotherm model while the Cr (VI) ions uptake onto FS and MFC adsorbents followed Freundlich isotherm model. The results of the kinetic studies showed that rate of Pb (II) removal followed pseudo second order model while the rate of adsorption of Cr (VI) onto the FS and MFC adsorbents best fitted pseudo first order model. Owing to its improved cation exchange capacity and eco-friendliness, the modified feldspar composite have a good potential application in wastewater treatment besides other industrial explorations.

In this study modified feldspar composite (MFC) was prepared from the combination of Theobroma cacao pod (TCP) and feldspar (FS) using calcination method. The Theobroma cacao pod-feldspar sample was first Na-modified by treatment using 0.1M NaOH solution before calcination in the muffle furnace at 3000C to complete the process of composite preparation. The Theobroma cacao pods (TCP), feldspar (FS) and modified feldspar composite (MFC) were characterized using XRF, X-ray diffraction (XRD), Brunauer Emmett and Teller ( BET) analysis, scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR). The results showed that the cation exchange capacity of the modified feldspar composite (30.66 ± 0.21 meq/100 g) was 5 times higher than that of raw feldspar (6.42 ± 0.45 meq/100g). More so, the novel biohybrid material, MFC has a surface area of 53.60 ± 0.3 m2/g and particle size of 105.4 ± 0.18. The XRD patterns revealed that after the modification process, there is only slight shift in the position of some diffraction peaks of feldspar and the composite material indicating the retention of the crystalline properties of the feldspar in the novel composite (MFC). FTIR results showed that some functional groups present in the two starting materials were also available on the surface of the composite (MFC) indicating that the intercalation of TCP biomass into feldspar surface was successful. Owing to its improved cation exchange capacity and eco-friendliness, the modified feldspar composite (MFC) has a good potential application as adsorbent for heavy metals in wastewater treatment besides other industrial explorations.

In this study modified feldspar composite (MFC) adsorbent based on feldspar and Theobroma cacao pods (TCP) was prepared using calcination method, characterized and tested for the removal As (III) from aqueous solution. The results showed that the cation exchange capacity of the modified feldspar composite (30.66 ± 0.21 meq/100 g) was 5 times higher than that of raw feldspar (6.42 ± 0.45 meq/100g). More so, the novel biohybrid material, MFC has a surface area of 53.60 ± 0.3 m2/g and particle size of 105.4 ± 0.18. Response surface methodology (RSM) via central composite design (CCD) was utilized in the optimization of the efficiency of As (III) ions uptake by the novel composite (MFC) in 20 experiment runs. The optimization results revealed that predicted adsorption percentages of (99.72%) for As (III) ions was close to the experimental results (99.98%) for the metal ions at the optimum conditions of adsorption parameters (pH 5; 0.5 g; 100 mg/L; 120 min and 3280K). The adequacy and validation of the model was justified with the good agreement between R2 values (0.9959) and adjusted R2 (0.9981) and higher F values (≥ 147) from the analysis of variance (ANOVA) results. Furthermore, the results from isotherm studies showed that As (III) ions adsorption onto the adsorbent best fitted the Langmuir isotherm model, hence chemisorption process. The results of the kinetic studies showed that the rate of uptake of As (III) ions onto MFC active sites followed pseudo second order kinetic model. The Intraparticle diffusion though not the only rate - controlling step, played an important role in the metal ions uptake by the adsorbent. The thermodynamic results revealed that As (III) adsorption onto MFC surface was feasible, spontaneous with negative ∆H values, suggestive of exothermic process. The MFC, owing to its abundance and other properties as its improved cation exchange capacity and eco-friendliness has a good potential as a highly efficient alternative adsorbent to commercial activated carbons in water treatment.