Process Optimization and Modeling the Adsorption of Polycyclic Aromatic-Congo Red Dye onto Delonix regia Pod-Derived Activated Carbon

The efficiency of Raphia hookeri adsorbent in indigo carmine dye removal: Economy depth via chemometrics

The remediation of dye pollutants remains a concern in contemporary water management practices. Hence, the need for efficient and cost-effective techniques for dye removal from wastewater. In this study, the epicarp of Raphia hookeri fruits was treated with orthophosphoric acid for enhanced porosity and efficiency in the uptake of Indigo carmine dye (ICD). Treated Raphia hookeri fruit waste (RHPW) presented morphologically distributed pores as well as high porosity with Branneur-Emmet-Teller (BET) surface area of 945.43 m2/g. RHPW displayed functional groups suitable for adsorption. The maximum ICD uptake was observed at pH 5 while the maximum uptake (qmax) was 20.41 mg/g in the concentration range of 2-10 mg/L. Freundlich isotherm and Pseudo-second order kinetics well-described equilibrium and kinetics data respectively. This indicated a multilayered adsorption. The Dubinin-Radushkecich model energy value was 40.82 kJ/mol, indicating chemical adsorption. The ridge regression, the Lasso and the Elastic net statistical models were used to establish a positive relationship between the various adsorption operational parameters studied. Lasso provided the best result based on the estimated mean squared error. The RHPW-ICD adsorption system was more favorable at room temperature, as the removal efficiency decreased with temperature rise. The findings established Raphia hookeri fruit epicarp as an economical and sustainable precursor for the preparation of potent adsorbent for Indigo carmine dye removal. This can find possible application in wastewater treatment.

Sorption Behavior of Azo Dye Congo Red onto Activated Biochar from Haematoxylum campechianum Waste: Gradient Boosting Machine Learning-Assisted Bayesian Optimization for Improved Adsorption Process

This work aimed to describe the adsorption behavior of Congo red (CR) onto activated biochar material prepared from Haematoxylum campechianum waste (ABHC). The carbon precursor was soaked with phosphoric acid, followed by pyrolysis to convert the precursor into activated biochar. The surface morphology of the adsorbent (before and after dye adsorption) was characterized by scanning electron microscopy (SEM/EDS), BET method, X-ray powder diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) and, lastly, pHpzc was also determined. Batch studies were carried out in the following intervals of pH = 4-10, temperature = 300.15-330.15 K, the dose of adsorbent = 1-10 g/L, and isotherms evaluated the adsorption process to determine the maximum adsorption capacity (Qmax, mg/g). Kinetic studies were performed starting from two different initial concentrations (25 and 50 mg/L) and at a maximum contact time of 48 h. The reusability potential of activated biochar was evaluated by adsorption-desorption cycles. The maximum adsorption capacity obtained with the Langmuir adsorption isotherm model was 114.8 mg/g at 300.15 K, pH = 5.4, and a dose of activated biochar of 1.0 g/L. This study also highlights the application of advanced machine learning techniques to optimize a chemical removal process. Leveraging a comprehensive dataset, a Gradient Boosting regression model was developed and fine-tuned using Bayesian optimization within a Python programming environment. The optimization algorithm efficiently navigated the input space to maximize the removal percentage, resulting in a predicted efficiency of approximately 90.47% under optimal conditions. These findings offer promising insights for enhancing efficiency in similar removal processes, showcasing the potential of machine learning in process optimization and environmental remediation.

Chitosan/lemon residues activated carbon efficiently removal of acid red 18 from aqueous solutions: batch study, isotherm and kinetics

In this research, chitosan-decorated activated carbon (AC-CS) was proposed. The AC was cross-linked with glutaraldehyde to prepare an adsorbent (AC-CS). The AC-CS has a rough surface. Adding the AC-CS directly to the dye solution can achieve simple and convenient removal of anionic azo dyes acid red 18 (AR-18). In the dye solution, the AC-CS was used as an adsorbent. The effects of pH, contact time, temperature, initial concentration of AR-18 and the AC-CS dosage on the adsorption efficiency were investigated. Full kinetic and isotherm analyses were also undertaken. In addition, the reusability of the AC-CS was evaluated, and the results showed that the removal rate of AR18 after regeneration remained relatively stable, above 90%. This experiment has shown that AC-CS is a promising anionic azo dye adsorbent.

Adsorption of crystal violet on activated bamboo fiber powder from water: preparation, characterization, kinetics and isotherms

Biomass-activated carbon has made a great contribution as an adsorbent in the field of dye wastewater treatment. In this study, the response surface method (RSM) based on the Box-Behnken design was used to optimize the preparation process. Bamboo fiber activated carbon (BAC) with a specific surface area of 2892 m² g^-1 and a pore volume of 1.80 cm³ g^-1 was prepared. Various characterization methods (SEM, XPS, XRD, and Raman spectroscopy) were used to analyze the micro-structure of BAC. In the microscopic state, the BAC is fibrous and maintains the originally connected pores of the bamboo fiber. After high-temperature activation, the microcrystallinity of BAC decreases, and the degree of graphitization is low, indicating the presence of amorphous carbon. The adsorption capacity of BAC to crystal violet in simulated wastewater was evaluated via an adsorption experiment. Under the following conditions: the dosage of BAC was 0.04 g, the concentration was 600 mg L^-1, the adsorption temperature and time were 25 °C and 30 min, respectively, and the as-prepared BAC had a 99.96% removal rate. The adsorption process conformed to the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, indicating that the adsorption process of CV on BAC belonged to monomolecular layer adsorption. The adsorption process occurs spontaneously and is accompanied by heat release, and the maximum adsorption capacity of BAC within a given concentration range could reach 1353.09 mg g^-1. SEM-EDS characterization before and after adsorption showed that ion exchange and the presence of oxygen-containing functional groups played an important role in promoting the adsorption process. The results show that BAC considerably affects CV removal, which has great application prospects.

Reutilization of waste biomass from sugarcane bagasse and orange peel to obtain carbon foams: Applications in the metal ions removal

The high levels of heavy metals contained in residual water and the pollution generated by a large amount of unexploited agro-industrial waste are a serious problem for the environment and mankind. Therefore, in the present work, with the aim of treating and reducing the pollution caused by heavy metal ions (Pb, Cd, Zn and Cu), activated carbons (ACs) were synthesized from sugarcane bagasse (SCB) and orange peel (OP) by means of physical - chemical activation method in an acid medium (H₃PO_4, 85 wt%) followed by an activation at high temperature (500 and 700 °C). Thereafter, these materials were used to produce carbon foams (CF) by the replica method and to evaluate their adsorbent capacity for the removal of heavy metals from synthetic water. XRD, FTIR, DLS, BET, Zeta Potential (ζ), SEM-EDS and AAS were used to investigate their structures, surface area, pore size, morphology, and adsorption capacity. The results show that as-prepared CF have a second level mesoporous structure and AC present a micro-mesoporous structure with a pore diameter between 3 and 4 nm. The experimental adsorption capacities of heavy metals showed that the CF from OP present a better elimination of heavy metals compared to the AC; exhibiting a removal capacity of 95.2 ± 3.96% (Pb) and 94.7 ± 4.88% (Cu) at pH = 5. The adsorption values showed that the optimal parameters to reach a high metal removal are pH values above 5. In the best of cases, the minimum remaining concentration of lead and copper were 2.4 and 2.6 mg L^-1, respectively. The experimental data for carbon adsorbents are in accordance with the Langmuir and BET isotherms, with R² = 0.99 and the maximum homogenous biosorption capacity for lead and copper was Q_max = 968.72 and 754.14 mg g^-1, respectively. This study showed that agro-industrial wastes can be effectively retrieved to produce adsorbents materials for wastewater treatment applications.