Pyrolysis of rubber seed pericarp biomass treated with sulfuric acid for the adsorption of crystal violet and methylene green dyes: an optimized process.

In this study, the biomass of rubber seed pericarp was first treated with sulfuric acid and then its activated carbon was formed by the pyrolysis process. As produced acid-treated activated carbon of chosen biomass was then used for the adsorption of crystal violet (CV) and methylene green (MG) from the colored aqueous solution. The adsorbent was exposed to several characterization methods to know its structural and morphological behaviors before and after CV and MG adsorption. The adsorbent was found to be mesoporous having a surface area of 59.517 m2/g. The effect of pH, time, and concentration was assessed while various isotherm and kinetics models were employed to know the adsorption insight. The optimum conditions were at pH 8, within 30 min, 50 mg/L concentration, and 0.06 gm dose. The adsorption data (the maximum adsorption capacity for CV and MG were found to be 302.7 and 567.6 mg/g, respectively) was validated by fitting in a response surface statistical methodology and the positive interactions between the studied factors were found. The adsorption was mainly belonging to the electrostatic attraction of the dye molecules. The study proves that the used adsorbent is economical and an excellent source of treating wastewater.

The novelty of this research work comes from the conversion of the abundant biomass waste namely rubber seed pericarp into sulfonated-rich carbon material by pyrolysis process to be an efficient adsorbent for two structurally different cationic dyes. Furthermore, statistical optimization by using response surface methodology was applied to optimize the adsorption key parameters.

Fruit peel-based mesoporous activated carbon via microwave assisted K2CO3 activation: Box Behnken design and desirability function for methylene blue dye adsorption.

A low-cost fruit waste namely watermelon peel (WMP) was utilized as a promising precursor for the preparation of mesoporous activated carbon (WMP-AC) via microwave assisted-K2CO3 activation. The WMP-AC was applied as an adsorbent for methylene blue dye (MB) removal. Several types of characterizations, such as specific surface area (BET), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), Elemental Analysis (CHNS/O), and Fourier Transform Infrared Spectroscopy (FTIR) were used to identify the physicochemical properties of WMP-AC. Furthermore, Box-Behnken design (BBD) was applied to optimize the influence of the adsorption operational variables (contact time, adsorbent dose, working temperature, and solution pH) on MB dye adsorption. Thus, based on significant interactions, the optimum BBD output shows the best removal of 50 mg·L-1 MB (92%) was recorded at an adsorbent dose of 0.056 g, contact time of 4.4 min, working temperature of 39 °C, and solution pH 8.4. The Langmuir uptake capacity of WMP-AC was found to be 312.8 mg·g-1, with the best fitness to the pseudo-second-order kinetics model and an endothermic adsorption process. The adsorption mechanisms of MB by WMP-AC can be assigned to the hydrogen bonding, electrostatic attraction, and π-π stacking. The findings of this study indicate that WMP is a promising precursor for producing porous activated carbon for MB dye removal.

The novelty of this research work comes from the conversion of the domestic fruit waste namely watermelon peels into mesoporous activated carbon by the fast and convenient activation method of microwave-assisted chemical activation. The produced activated carbon was applied for the removal of a toxic organic dye. Furthermore, the statistical optimization by using response surface methodology was applied to optimize the adsorption key parameters.