Acetaminophen removal by calcium alginate/activated hydrochar composite beads: Batch and fixed-bed studies.

The occurrence of acetaminophen in surface water has been reported worldwide, indicating the need of alternative wastewater treatments. Activated hydrochar (AHC) is efficient for pharmaceuticals removal. Powdered AHC presents challenges that hamper its expansion. However, these issues can be overcome by adding polymers, such as alginate, in composite beads. Therefore, the present study aimed to develop and characterize alginate/brewer's spent grain AHC beads, applying them to acetaminophen adsorption in batch and fixed-bed experiments. The adsorbent presented a high surface area (533.42 m2 g-1) and Fourier-transform infrared spectroscopy (FTIR) showed that alginate assigned new functional groups to the composite. Batch studies revealed an endothermic behavior and maximum adsorption capacity of 165.94 mg g-1, with an equilibrium time of 240 min. The fixed-bed maximum adsorption capacity was 127.01 mg g-1, with a mass transfer zone of 5.89 cm. The importance of alginate for the adsorbent development has been successfully proven.

Physico-chemical and electrostatic surface characterisation of mica mineral and its applicability on the adsorption of Safranin Orange and Reactive Black 5 dyes.

ABSTRACTThe combined approach of specific surface area (SSA), porosity, microprobe analysis (EMPA), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with EDX and infrared spectroscopy (FTIR) provided the mica mineral physico-chemical and morphological characterisation. The electrostatic surface properties were assessed through the determination of the Point of Zero Charge (pHPZC) by the drift method and the electrokinetic mica mineral features represented by the Isoelectric Point (pHIEP) which was carried out through zeta potential measurements. Adsorption tests were performed to correlate the surface charge behaviour of the mica mineral and its influence on the adsorption efficiency of two different dyes, namely: Safranin Orange (SO), as a cationic dye and Reactive Black 5 (RB5), as an anionic dye. The higher adsorption capacity SO dye was observed at pH 9 and achieved almost 83% of removal, while RB5 dye adsorption on mica surface had the highest result, about 45% of removal efficiency, on pH of 3. In both cases, the main mechanism identified that drove this results is the electrostatic force of attraction between the adsorbent edge surface charge (pH-dependent) and the ionic nature (anionic or cationic) of the pollutant dyes particles. The preliminary adsorption experiments demonstrated that the raw grounded mica mineral has a greater potential associated with its application on cationic dye removal in wastewater. The present study aimed to detail the main characteristics of the mica mineral in order to evaluate the potential use of such mineral residues in the removal efficiency of contaminated wastewater.

Adsorption of Safranin-O dye by copper oxide nanoparticles synthesized from Punica granatum leaf extract.

The development of new technologies for water and wastewater treatment is a growing need due to the occurrence of micropollutants, such as dyes, in water resources. In this sense, green-synthesized nanoparticles are being extensively studied, due to their low cost, non-toxicity, and high efficiency in adsorption processes. Thus, the present study reports the green synthesis of copper oxide nanoparticles (CuO-NP), obtained from pomegranate (Punica granatum) leaf extract, employed for the removal of Safranin-O (SO) dye. CuO-NP was characterized by physicochemical analysis. These analyzes suggested that the redox process occurred efficiently. Also, the material presented interesting elements for the removal of cationic dyes such as negative surface charge, high specific surface area, and predominance of mesopores. The kinetic data fitted the pseudo-second-order model, reaching equilibrium in 480 min. The equilibrium study resulted in a maximum adsorption capacity of 189.54 mg g-1 at 298 K and the experimental data best fitted the Langmuir model. The effect of pH and ionic strength did not present significant changes, which demonstrates an advantage of this adsorbent over other materials. The regeneration study allowed to verify the possibility of reuse CuO-NP, since after 4 cycles the adsorption capacity was 44% of the initial value. Considering the results found, CuO-NP has a high potential for applicability in the treatment of water contaminated by dyes.

Modified Moringa oleifera Lam. Seed husks as low-cost biosorbent for atrazine removal.

Atrazine is an herbicide which is widely applied in sugarcane and corn crops. Its frequent use has resulted in environmental impacts, and its traces have been verified in surface and groundwater. Thus, it is necessary to remove this pollutant, and an alternative is the adsorption due to its universal nature, low-cost and ease of operation. Therefore, the objective of the present work was to study the adsorption capacity of atrazine by modified Moringa oleifera Lam. seed husks, a low-cost adsorbent. The biosorbent was subjected to c hemical and thermal treatment and was characterised by structural, morphological and textural analysis, which showed porous and heterogeneous characteristics, with a specific surface area of 5.77 m2 g-1. The kinetic study demonstrated equilibrium at 1200 min, with an adsorption capacity of 1.90 mg g-1 and the best fit was for the pseudo-second-order model. The isotherms were obtained at 298, 308 and 318 K. The Freundlich, Temkin and Langmuir models were applied to the experimental data, the latter being the best. The values of the thermodynamic parameters indicated that the biosorption was spontaneous, endothermic and reversible. The highest adsorption capacity obtained was 10.32 mg g-1, which was higher than several values found in the literature. The biosorbent was regenerated over three cycles, indicating its potential of atrazine removal from surface water.

Chitosan, alginate and other macromolecules as activated carbon immobilizing agents: A review on composite adsorbents for the removal of water contaminants.

Activated carbon (AC) is widely used in water treatment, however, it has some technical disadvantages, such as its high cost and difficulty to recover. To overcome these drawbacks, AC particles have been encapsulated within a polymeric support, mainly chitosan and alginate-based. The use of these biological macromolecules results in composites with lower-cost, superior mechanical properties, and higher number of functional groups, advantages that have been attracted the attention of the scientific community. However, the number of publications is relatively low, demonstrating an important research gap yet to be investigated. Thus, this paper aims to review the recent studies concerning the use of chitosan, alginate and other macromolecules as AC immobilizing agents, describing the synthesis methods, characterization analyses and adsorption studies, focusing on the main advantages, disadvantages, gaps and future perspectives. Throughout the review it was verified that the composites were able to remove several water contaminants, mainly dyes and heavy metals, with high efficiency. Synergistic effects were detected, indicating the role of both polymers and AC, which increased the spectrum of contaminants capable of being adsorbed. Finally, it was observed a gap in column experiments, suggesting that future studies are essential to elucidate the applications in the industrial perspective.

Activated hydrochar produced from brewer's spent grain and its application in the removal of acetaminophen.

Acetaminophen has shown a gradual increase in detection in surface waters. Although present in low concentrations, it should be removed to prevent deleterious effects. Thus, adsorption onto activated carbon is emphasized. Adsorbents may be produced by hydrothermal carbonization (HTC), an environmental-friendly process. Therefore, this work aimed to investigate the use of HTC, verifying its application in acetaminophen removal. Brewer's spent grain (BSG), its hydrochar (HC-BSG) and its activated hydrochar (AHC-BSG) were characterized. HTC provided material with high carbon content. Lignocellulosic breakdown has been demonstrated in HC-BSG and AHC-BSG, but in the latter it was more intense as a result of activation with KOH. Also, a high surface area was found in AHC-BSG (1512.83 m2 g-1), resulting in an adsorption of 318.00 mg g-1. The pseudo-second-order and Langmuir models were fitted to the experimental data. Therefore, HTC was effective as a pretreatment for AHC-BSG, resulting in significant acetaminophen removals.

Development of a new low-cost adsorbent functionalized with iron nanoparticles for removal of metformin from contaminated water.

An adsorbent was developed from the residues of Moringa oleifera Lam. seed husks functionalized with iron nanoparticles for subsequent application to the removal of metformin from contaminated water. The material, MOM-Fe3O4, was characterized using TEM, SEM imaging, and EDX analysis, which revealed that iron nanoparticles were retained in the pores. The application of MOM-Fe3O4 to waste water resulted in a 93.9% reduction in the metformin content, demonstrating the efficacy of the material. Kinetic and equilibrium data were fitted to the pseudo-first-order and Langmuir models, respectively. The thermodynamic parameters indicated an exothermic and reversible process. A high adsorption capacity, 65.01 mg g-1 at 298 K, demonstrated the potential of using the new material as a low-cost adsorbent for the removal of pharmaceuticals such as metformin.

Surface water pollution by pharmaceuticals and an alternative of removal by low-cost adsorbents: A review.

Micropollutants, also called emerging contaminants, consist of an extensive group of synthetic and natural substances, including pharmaceuticals, personal care products, steroid hormones, and agrochemicals. Currently, the monitoring of residual pharmaceuticals in the environment has been highlighted due to the fact that many of these substances are found in wastewater treatment plants effluents and surface waters, in concentrations ranging from ng L-1 to µg L-1. Most of these compounds are discharged into the environment continuously through domestic sewage treatment systems. In the present work, it is presented an overview of water pollution by these pollutants, as well as a review of the recent literature about the use of low-cost adsorbents for the removal of the main pharmaceuticals found in surface water, focusing on municipal and agroindustrial wastes as precursors. It was possible to observe several examples of high adsorption capacities of these compounds with such materials, however other aspects must be considered in order to evaluate the real applicability in water and wastewater treatment, such as competition, recyclability and production cost.