Abstract
In this study, a response surface methodology (RSM) approach using central composite design (CCD) was investigated to develop a mathematical model and to optimize the effects of pH, adsorbent amount and temperature related to the hexavalent chromium removal by biosorption on peanut shells (PSh). The highest removal percentage of 30.28% was found by the predicted model under the optimum conditions (pH of 2.11, 0.73 g of PSh and 37.2 °C) for a 100 mg/L initial Cr(VI) concentration, which was very near to the experimental value (29.92%). The PSh was characterized by SEM, EDX, FTIR, BET, XRD analyses. Moreover, a Langmuir isotherm fitted well (R2 = 0.992) with the experimental data, and the maximum adsorption capacity was discovered to be 2.48 and 3.49 mg/g respectively at 25 and 45 °C. Kinetic data were well foreseen by pseudo second order. Thermodynamic study depicted that biosorption of Cr(VI) onto PSh was spontaneous and endothermic. Regeneration of the PSh using NaOH showed a loss <5% in the Cr(VI) removal efficiency up to three recycle runs. In summary, the Cr(VI) removal onto economic, sensitive and selective biosorbent (PSh) was optimized using CCD to study biosorption behaviors.
Highlights
Wastewater pollution by chromium is of major concern due to the excessive amount generated by various industries using processes that retain a chromium finish treatment, which is destructive to the environment and human health (Jobby et al 2018)
The intersection of the curve final pH 1⁄4 f with the bisector corresponds to the pHpzc of peanut shells (PSh) as shown in Figure 1 was equal to 4.6
The value of the adjusted coefficient of determination R2 1⁄4 0.972 showed that the % removal of Cr(VI) predicted by the model was correlated with that found experimentally
Summary
Wastewater pollution by chromium is of major concern due to the excessive amount generated by various industries using processes that retain a chromium finish treatment, which is destructive to the environment and human health (Jobby et al 2018). Studies have revealed that Cr(VI) is among the 14 most toxic chemicals posing a threat to humans even at ppb concentrations (Pradhan et al 2017). It can penetrate into the body through the skin, digestion, the respiratory tract and mucous membranes (Li et al 2021). The World Health Organization (WHO) recommended a maximum allowed concentration of Cr(VI) to 0.05 and 0.5 mg/L respectively in drinking water and industrial wastewater (Aigbe & Osibote 2020)
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