Efficient removal of cationic dye using ZIF-8 based sodium alginate composite beads: Performance evaluation in batch and column systems

Pinecone biochar for the Adsorption of chromium (VI) from wastewater: Kinetics, thermodynamics, and adsorbent regeneration

High concentration of chromium in aquatic environments is the trigger for researchers to remediate it from wastewater environments. However, conventional water treatment methods have not been satisfactory in removing chromium from water and wastewater over the last decade. Similarly, many adsorption studies have been focused on one aspect of the treatment, but this study dealt with all aspects of adsorption packages to come up with a concrete conclusion. Therefore, this study aimed to prepare pinecone biochar (PBC) via pyrolysis and apply it for Cr(VI) removal from wastewater. The PBC was characterized using FTIR, SEM-EDX, BET surface area, pHpzc, Raman analyses, TGA, and XRD techniques. Chromium adsorption was studied under the influence of PBC dose, solution pH, initial Cr(VI) concentration, and contact time. The characteristics of PBC are illustrated by FTIR spectroscopic functional groups, XRD non-crystallite structure, SEM rough surface morphology, and high BET surface area125 m2/g, pore volume, 0.07 cm3/g, and pore size 1.4 nm. On the other hand, the maximum Cr (VI) adsorption of 69% was found at the experimental condition of pH 2, adsorbent dosage 0.25 mg/50 mL, initial Cr concentration 100 mg/L, and contact time of 120 min. Similarly, the experimental data were well-fitted with the Langmuir adsorption isotherm at R2 0.96 and the pseudo-second-order kinetics model at R2 0.99. This implies the adsorption process is mainly attributed to monolayer orientation between the adsorbent and adsorbate. In the thermodynamics study of adsorption, ΔG was found to be negative implying the adsorption process was feasible and spontaneous whereas the positive values of ΔH and ΔS indicated the adsorption process was endothermic and increasing the degree of randomness, respectively. Finally, adsorbent regeneration and reusability were successful up to three cycles. In conclusion, biochar surface modification and reusability improvements are urgently required before being applied at the pilot scale.

Biopolymer-based beads for the adsorptive removal of organic pollutants from wastewater: Current state and future perspectives

Among biopolymer-based adsorbents, composites in the form of beads have shown promising results in terms of high adsorption capacity and ease of separation from the effluents. This review addresses the potential of biopolymer-based beads to remediate wastewaters polluted with emerging organic contaminants, for instance dyes, active pharmaceutical ingredients, pesticides, phenols, oils, polyaromatic hydrocarbons, and polychlorinated biphenyls. High adsorption capacities up to 2541.76 mg g-1 for dyes, 392 mg g-1 for pesticides and phenols, 1890.3 mg g-1 for pharmaceuticals, and 537 g g-1 for oils and organic solvents have been reported. The review also attempted to convey to its readers the significance of wastewater treatment through adsorption by providing an overview on decontamination technologies of organic water contaminants. Various preparation methods of biopolymer-based gel beads and adsorption mechanisms involved in the process of decontamination have been summarized and analyzed. Therefore, we believe there is an urge to discuss the current state of the application of biopolymer-based gel beads for the adsorption of organic pollutants from wastewater and future perspectives in this regard since it is imperative to treat wastewater before releasing into freshwater bodies.

Exploring the structural characteristics and dye removal capabilities of powder-, granule- and film- shaped magnetic activated carbon derived from Oleaster seed

Dye pollution in water caused by excessive discharge of industrial effluent has become a major environmental problem in recent decades because of its irreversible effects on human health. In this study, low-cost carbon-based adsorbents synthesized from Oleaster seed (OS) were prepared in three forms of powder (PAC), film (FAC), and granule (GAC) and used for the removal of methylene blue dye. The properties of the synthesized adsorbents were characterized by SEM-EDX, BET, XPS and FTIR analyses. The maximum adsorption capacity (qmax) of PAC, FAC, and GAC adsorbents were obtained as 68.49, 32.25, and 15.10 mg/g, respectively at the optimum experimental conditions of pH = 10, adsorbent dosages of 0.5, 1, and 2 g/l, contact times of 60, 90, and 120 min, dye concentration of 10 mg/L, and temperature of 25°C. The Langmuir isotherm well described the equilibrium data for all three adsorbents. The pseudo-second-order kinetic model provided the best fit with the adsorption data obtained from all three adsorbents. Adsorption occurred spontaneously through a combination of chemical and physical mechanisms, with a thermodynamically exothermic process. The desorption experiments demonstrated that all the adsorbents have substantial potential for recovery. The novel activated carbon/alginate composite films are proposed as more promising biosorbents to remove MB dye from the aquatic environment compared to GAC adsorbents.

Efficient adsorptive removal of used drugs during the COVID-19 pandemic from contaminated water by magnetic graphene oxide/MIL-88 metal-organic framework/alginate hydrogel beads

Currently, the presence of drugs used in the COVID-19 pandemic in water bodies is worrisome due to their high toxicity, which necessitates their critical removal by developing highly efficient adsorbents. Hence, in this study, alginate hydrogel beads of magnetic graphene oxide@MIL-88 metal-organic framework (GO@Fe3O4@MIL-88@Alg) were prepared for the first time and then utilized as a new absorption system for the removal of COVID-19 drugs such as doxycycline (DOX), hydroxychloroquine (HCQ), naproxen (NAP), and dipyrone (DIP) from aqueous solutions by batch adsorption manner. The effects of different experimental factors, such as adsorbent dosage, contact time, pH, drug concentration, temperature, ionic strength, presence of an external magnetic field (EMF), and magnet distance from the adsorption flask were optimized for the removal of COVID-19 drugs. The adsorption equilibrium isotherm proved that the adsorption process of DOX, HCQ, NAP, and DIP drugs on GO@Fe3O4@MIL-88@Alg hydrogel beads conformed to the Langmuir model and followed the pseudo-second-order adsorption kinetics. The maximum adsorption capacities of DOX, HCQ, NAP, and DIP drugs obtained for GO@Fe3O4@MIL-88@Alg hydrogel beads with the Langmuir model were 131.57, 79.92, 55.55, and 49.26 mg/g at 298 K, respectively. The thermodynamic study suggested a spontaneous endothermic adsorption process. Also, the conclusion from this study confirmed the validity of GO@Fe3O4@MIL-88@Alg hydrogel beads for excellent removal of COVID-19 drugs from water samples. It was also found that the GO@Fe3O4@MIL-88@Alg hydrogel beads could be reused with satisfactory removal efficiency in six cycles. Based on the study, the GO@Fe3O4@MIL-88@Alg hydrogel beads could be considered a sustainable, simple, economical, environmentally friendly absorption system for the removal of pharmaceutical contaminants from water.