Investigating mixed biosolids and cardboard for methylene blue adsorption: Activation, adsorption modelling and thermodynamics

Mesoporous magnetic biochar derived from common reed (Phragmites australis) for rapid and efficient removal of methylene blue from aqueous media

A novel mesoporous magnetic biochar (MBC) was prepared, using a randomly growing plant, i.e., common reed, as an exporter of carbon, and applied for removal of methylene blue (MB) from aqueous solutions. The prepared sorbent was characterized by nitrogen adsorption/desorption isotherm, saturation magnetization, pH of point of zero charges (pHPZC), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The obtained MBC has a specific surface area of 94.2 m2 g-1 and a pore radius of 4.1 nm, a pore volume of 0.252 cm3 g-1, a saturation magnetization of 0.786 emu g-1, and a pHPZC of 6.2. Batch adsorption experiments were used to study the impact of the physicochemical factors involved in the adsorption process. The findings revealed that MB removal by MBC was achieved optimally at pH 8.0, sorbent dosage of 1.0 g L-1, and contact time of 30 min. At these conditions, the maximum adsorption was 353.4 mg g-1. Furthermore, the adsorption isotherm indicated that the Langmuir pattern matched well with the experimental data, compared to the Freindlich model. The ∆G was - 6.7, - 7.1, and - 7.5 kJ mol-1, at 298, 308, and 318 K, respectively, indicating a spontaneous process. The values of ∆H and ∆S were 5.71 kJ mol-1 and 41.6 J mol-1 K-1, respectively, suggesting endothermic and the interaction between MB and MBC is van der Waals type. The absorbent was regenerated and reused for four cycles after elution with 0.1 mol L-1 of HCl. This study concluded that the magnetic biochar generated from common reed has tremendous promise in the practical use of removing MB from wastewater.

Adsorption behavior and mechanism of modified Pinus massoniana pollen microcarriers for extremely efficient and rapid adsorption of cationic methylene blue dye

Herein, a novel biosorbent was successfully fabricated through a two-step process employing Pinus massoniana pollen as raw material. The efficacy of this biosorbent in eliminating methylene blue (MB), a typical organic cationic dye, from highly concentrated industrial wastewater was investigated. The results demonstrated that by adjusting the wettability of pollen microcarriers, it is possible to significantly increase their adsorption capacity for cationic dyes, resulting in a remarkable 25-fold improvement. The modified Pinus massoniana pollen microcarriers (MPPMC) exhibited an optimal adsorption capacity (585 mg/g) under specific conditions and a rapid equilibrium (97.6% in 5 min, uptake 487.8 mg/g) even at room temperature, showing excellent performance in removing MB efficiently and quickly. It is worth noting that the modified microcarriers could be regenerated via a simple pH-controlled adsorption-desorption cycle, maintaining their superior efficiency (> 99%) even after undergoing five cycles, indicating their excellent reproducibility. The MB adsorption process on MPPMC obeyed the pseudo-second-order kinetic model and followed the Langmuir model. Through the introduced modifications, the substantial deprotonation of carboxyl groups notably augmented electrostatic and hydrogen bonding interactions between MPPMC and MB. Overall, this study offers a sustainable, eco-friendly biological adsorbent, and the MPPMC exhibit the considerable potential for efficient and rapid removal of organic cationic dyes in wastewater.

Expermental investigation on adsorption of methylene blue dye from waste water using corncob cellulose-based hydrogel

Hydrogel from corncob cellulose was synthesized in this investigation. The synthesized Hydrogel was characterized by SEM, XRD, and FTIR instruments. As the results indicate the synthesized hydrogel has required and important features, these suggest the suitability of hydrogel for the adsorption of methylene blue dye (MBD). Three important process variables (dosage, contact time, and initial concentration) with three levels were studied during the adsorption process at 30 °C and neutral pH. The efficiency of hydrogel for adsorption of MBD was determined in each experiment. The experimental results were statistically analyzed and interpreted. The maximum removal efficiency was achieved at 2.22 g/L of dosage, 80.36 min of contact time, and 74.54 mg/L of initial concentration. At this condition, 98.25% of MBD was achieved through experimental tests. Kinetics, isotherm, and thermodynamics studies were performed. Langmuir isotherm is more suitable to describe the adsorption process and the Pseudo second-order kinetic model fits this process. From the thermodynamics studies, all negative values of change in Gibbs free energy (ΔG°), and positive value of change in enthalpy (ΔH°), and change in entropy (ΔS°) indicate that the carried out experimental process is a spontaneous and endothermic. Moreover, the regeneration experiment for adsorbent was performed. The treatment of real textile industry waste water was conducted and the removal efficiency of hydrogel was 64.76%. This removal percentage reduction from sythetic aqueous solution is due to involvement of other pollutants in the real waste water. The synthesized hydrogel adsorbent is suitable up to the third cycle without significant loss in removal efficiency.

Removal of methylene blue by acrylic polymer adsorbents loaded with magnetic iron manganese oxides: Synthesis, characterization, and adsorption mechanisms

Dyes pose significant risks for aquatic environments and biological health in general owing to their non-biodegradable nature, carcinogenicity, and toxicity. The effective treatment of dye wastewater has become an important research topic. In this study, acrylic polymers (AP) loaded with magnetic iron manganese oxides (MIMO) (AP/MIMO) were prepared and used for the first time for the adsorption of methylene blue (MB). Carbon in AP/MIMO exists predominantly in the C-H and C-C forms, with its content reaching 50.7%. Oxygen and nitrogen in AP/MIMO exist mainly in the -CO- and -N-C forms, with contents of up to 41.5% and 73.3%, respectively. MB removal by AP/MIMO was consistent with the pseudo-second-order kinetic model (R2 = 0.99), equilibrium was achieved within 20 min, and the highest MB capacity of 2611.23 mg g-1 was predicted by the Langmuir isotherm model (R2 = 0.91-0.94). AP/MIMO exhibited excellent MB adsorption performance in the pH range of 4-10, with a removal efficiency higher than 99.0% (MB = 100 mL 1000 mg L-1; AP/MIMO = 50 mg). Thermodynamic indicators, such as positive entropy (ΔS0; 98.30 J⋅mol-1⋅K-1), negative Gibbs free energy (ΔG0; -29.40, -28.50, and -27.50 KJ⋅mol-1), and positive enthalpy (ΔH0; 2.30 KJ⋅mol-1), demonstrated that MB removal by AP/MIMO was autonomous, favorable, and endothermic. In addition, the integration of experimental results and theoretical calculations verified that electrostatic interactions were the primary mechanism for MB adsorption at carboxyl sites on AP/MIMO. The total interaction energy between AP and MB was -310.43 kJ⋅mol-1, and the electrostatic effect had a decisive contribution to the MB adsorption, with a value of up to -341.06 kJ⋅mol-1. AP and MB were most likely bound by -COO and S atoms. Overall, AP/MIMO exhibits high adsorption capacity and shows potential as a high-performance magnetic polymer for MB removal.