Adsorption of glyphosate and metabolite aminomethylphosphonic acid (AMPA) from water by polymer-based spherical activated carbon (PBSAC)

Glyphosate (GLY) is the most commonly used herbicide worldwide, and aminomethylphosphonic acid (AMPA) is its main metabolite. Their occurrence in ground and surface waters causes diseases in humans, while complex physico-chemical properties hinder detection and effective removal. Polymer-based spherical activated carbon (PBSAC) can adsorb many micropollutants efficiently and, hence, overcome the shortfalls of conventional treatment methods. The static adsorption of a mixture of GLY and AMPA by PBSAC was investigated with varying PBSAC properties and relevant solution chemistry. The results show that PBSAC can remove 95% GLY and 57% AMPA from an initial concentration of 1 µg/L at pH 8.2. PBSAC properties (size, activation level, and surface charge) have a strong influence on herbicide removal, where surface area plays a key role. Low to neutral pH favors non-charge interactions and results in good adsorption, while higher temperatures equally enhance GLY/AMPA adsorption by PBSAC. The work demonstrated the effective removal of GLY to meet the European guideline concentration (0.1 µg/L), while AMPA could not be removed to the required level.

Adsorption and desorption of flavonoids on activated carbon impregnated with different metal ions

In this study, four metal ions Mg²⁺, Al³⁺, Fe³⁺, and Zn²⁺ were loaded on the surface of activated carbon by an impregnation method coupled with high-temperature calcination to prepare modified activated carbon. Scanning electron microscopy, specific surface area and pore size analysis, X-ray diffraction, and Fourier infrared spectroscopy were used to evaluate the structure and morphology of the modified activated carbon. The findings show that the modified activated carbon had a large microporous structure and high specific surface area, both of which significantly improved absorbability. This study also investigated the adsorption and desorption kinetics of the prepared activated carbon for three flavonoids with representative structures. The adsorption amounts of quercetin, luteolin, and naringenin in the blank activated carbon reached 920.24 mg g^-1, 837.07 mg g^-1, and 677.37 mg g^-1, while for activated carbon impregnated with Mg, the adsorption amounts reached 976.34 mg g^-1, 963.39 mg g^-1, and 817.98 mg g^-1, respectively; however, the desorption efficiencies of the three flavonoids varied a lot. The differences in desorption rates of naringenin as compared with quercetin and luteolin in the blank activated carbon were 40.13% and 46.22%, respectively, and the difference in desorption rates increased to 78.46% and 86.93% in the activated carbon impregnated with Al. The differences provide a basis for the application of this type of activated carbon in the selective enrichment and separation of flavonoids.

The electro-Fenton regeneration of Granular Activated Carbons: Degradation of organic contaminants and the relationship to the carbon surface

Electrochemical regeneration of Granular Activated Carbon is an emerging treatment option to restore adsorption capacity in systems designed to remove organic contaminants from aqueous solutions. The electro-Fenton process is one such electrochemical process and it is reviewed along with other members of its family including Photoelectro-Fenton and Heterogeneous electro-Fenton and electro-Fenton like reactions, for its ability to regenerate Granular Activated Carbons contaminated with organics. The behaviour of critical operating parameter such as pH, current, catalyst concentration and initial contaminant concentration are reviewed to find optimal operating conditions. The relationship between electro-Fenton regeneration and the chemical and physical surface of the carbon is also explored. Understanding regeneration mechanisms and the optimal operating conditions enables these technologies to be used commercially and to be scaled-up and treat contaminated waters more efficiently.

Removal of paracetamol from aqueous solution by containment composites

Storage of wastes leads to severe problems of water pollution and neighboring matrices due to the infiltration of landfill leachate. Uncontrolled landfill and waste storage can lead to groundwater pollution, which can lead to serious health problems for the living. Engineered barriers can be a solution to these pollution problems. The purpose of this study was to develop novel composite materials – clay-based, activated carbon, cement, and PVA polymer. These composites were intended for the containment of waste in landfill. The clay (70–80%) and activated carbon (5–15%) contents were varied to obtain three different geomaterials – GM1, GM2, and GM3. In the preparation of GM3, the content of activated carbon used was higher than for GM1 and GM2, paracetamol removal capacity tested by adsorption, experiments were influenced by parameters such as the adsorbent mass, the initial solute concentration, contact time, temperature, and pH effect. The parameter of initial paracetamol concentrations was studied using a range of 50, 100, and 150 mg L−1. For a GM3 mass of 80 mg, the adsorbed amount is 14.67 mg g−1, and the contact time is 180 minutes. This study revealed that composites are efficient for the treatment of landfill leachates.

Batch Adsorption and Column Leaching Studies of Aniline in Chinese Loess Under Different Hydrochemical Conditions

Through batch adsorption and column leaching experiments, this study aimed to investigate the adsorption and transport behavior of aniline in loess and related mechanism under different hydrochemical conditions. Batch experiments results indicated that aniline adsorption reached equilibrium after about 120 min, and the adsorption fitted the pseudo-second-order kinetic and Freundlich models well. The adsorption was spontaneous and exothermic process, indicating the aniline adsorbed by inherent colloidal particles (ICPs) tended to transport. Low pH value, ionic strength and temperature benefitted the adsorption. Column experiments results under different ionic strengths (100, 10 and 1 mM) confirmed the potential transport of aniline. The FT-IR spectra have further suggested that aniline was adsorbed by the ICPs through hydrogen-bond, hydrophobic effect and cation exchange interactions. Low ionic strength was advantageous for the adsorption of aniline in loess and the stabilities of ICPs in solution, but enhanced the co-transport probability of ICPs with aniline in loess.

Evaluation of an activated carbon disposal system for safe disposal of model prescription sedative medications

Lack of a safe and convenient disposal method for expired and unused medications may lead to many problems such as accidental exposure, intentional misuse, and food and water contamination. Activated carbon can offer safe disposal of medications due to its highly porous structure, which exerts strong physical adsorption forces with chemicals. This study aimed to evaluate the efficiency of an activated carbon-based drug disposal system for deactivating three model sedative prescription medications. Deactivation was performed by mixing the medication, activated carbon, and tap water. Desorption was evaluated by exposing the deactivation system to wash-out solutions. Rapid, precise, accurate, and sensitive HPLC-UV method for each drug was successfully developed, validated and employed. Results of the 28-day deactivation study showed that on average, more than 94.00% of drugs were rapidly deactivated within 8 hours. All drugs reached more than 99.00% deactivation by the end of 28-day period. Desorption study demonstrated that all medications were retained by the system, with insignificant amount of drug (0.25%) leached into the washout solutions within 24 hours. In conclusion, activated carbon rapidly and successfully deactivated the medications tested, suggesting activated carbon-based drug disposal system provides a convenient, secure, and effective method for unused medication.

Development and validation of an HPLC-UV method for analysis of methylphenidate hydrochloride and loxapine succinate in an activated carbon disposal system

Unused medications have the possibility of being abused, causing serious harm to individuals who were not prescribed the drug. The Food and Drug Administration (FDA) recommends the proper disposal of unused prescribed medications to maintain safety and prevent environmental hazards. However, many of the current disposal techniques do not properly address safety. A drug disposal pouch containing granular activated carbon offers a unique disposal method to deactivate residual or expired medication in a convenient, effective, and safe manner. A robust and validated method for methylphenidate hydrochloride and loxapine succinate was developed using high-performance liquid chromatography (HPLC) and the deactivation efficiency of the disposal system was tested. Methylphenidate hydrochloride was analyzed on a C₁₈ analytical column (250 mm × 4.60 mm, 100Å) using acetonitrile-water (0.05% (v/v) trifluoroacetic acid) as the mobile phase at a flow rate of 1.0 mL/min with a run time of 15 min and retention time of 7.8 min. Loxapine succinate was separated on a C₈ 100Å (250 mm × 4.6 mm, 5 µm) column maintained at 25 °C using a flow rate of 1.0 mL/min. The run time was 10 min and the retention time of the drug was around 4.6 min. Mobile phase was composed of acetonitrile and water (0.3% triethylamine) at pH 3.0 as 40:60 (v/v). Reference standard solutions (100 µg/mL) for both drugs were prepared by dissolving in mobile phases. These methods provide good linearity (R² = 0.999) over the range of 5–100 µg/mL for methylphenidate hydrochloride and 0.1–100 µg/mL for loxapine succinate. The assay methods were successfully applied to study the deactivation of these drugs.

Ligninolytic enzymes: Versatile biocatalysts for the elimination of endocrine-disrupting chemicals in wastewater

Direct municipal wastewater effluent discharge from treatment plants has been identified as the major source of endocrine‐disrupting chemicals (EDC) in freshwaters. Consequently, efficient elimination of EDC in wastewater is significant to good water quality. However, conventional wastewater treatment approaches have been deficient in the complete removal of these contaminants. Hence, the exploration of new and more efficient methods for elimination of EDC in wastewater is imperative. Enzymatic treatment approach has been suggested as a suitable option. Nonetheless, ligninolytic enzymes seem to be the most promising group of enzymes for EDC elimination, perhaps, owing to their unique catalytic properties and characteristic high redox potentials for oxidation of a wide spectrum of organic compounds. Therefore, this paper discusses the potential of some ligninolytic enzymes (laccase, manganese peroxidase, and versatile peroxidase) in the elimination of EDC in wastewater and proposes a new scheme of wastewater treatment process for EDC removal.

Soluble hydrocarbons uptake by porous carbonaceous adsorbents at different water ionic strength and temperature: something to consider in oil spills

Nowadays, petrochemical operations involve risks to the environment and one of the biggest is oil spills. Low molecular aromatics like benzene, toluene, and naphthalene dissolve in water, and because of their toxicological characteristics, these produce severe consequences to the environment. The oil spill cleanup strategies are mainly designed to deal with the heavy fractions accumulated on the water surface. Unfortunately, very limited information is available regarding the treatment of dissolved fractions.A commercial (Filtrasorb 400) and modified activated carbons were evaluated to remove benzene, toluene, and naphthalene from water, which are the most soluble aromatic hydrocarbons, at different ionic strengths (I) and temperatures (0-0.76 M and 4-25 °C, respectively). This allowed simulating the conditions of fresh and saline waters when assessing the performance of these adsorbents. It was found that the hydrocarbons adsorption affinity increased 12 % at a I of 0.5 M, due to the less negative charge of the adsorbent, while at a high I (≃0.76 M) in a synthetic seawater, the adsorption capacity decreased 21 % that was attributed to the adsorbent's pores occlusion by water clusters. Approximately, 40 h were needed to reach equilibrium; however, the maximum adsorption rate occurred within the first hour in all the cases. Moreover, the hydrocarbons adsorption and desorption capacities increased when the temperature augmented from 4 to 25 °C. On the other hand, thermally and chemically modified materials showed that the interactions between adsorbent-contaminant increased with the basification degree of the adsorbent surface.

Degradation of atrazine from the riparian zone with a PEC system based on an anode of N–S–TiO2 nanocrystal-modified TiO2 nanotubes and an activated carbon photocathode

In this study, we developed a photoelectrochemical (PEC) system based on an anode of N–S–TiO₂ nanocrystal-modified TiO₂ nanotubes and an activated carbon photocathode to degrade atrazine from the riparian zone.

Separation Strategies for Processing of Dilute Liquid Streams

Processing of dilute liquid streams in the industries like food, agro-, biotechnology, pharmaceuticals, environment, and so forth needs special strategy for the separation and purification of the desired product and for environment friendly disposal of the waste stream. The separation strategy adopted to achieve the goal is extremely important from economic as well as from environmental point of view. In the present paper we have reviewed the various aspects of some selected universal separation strategies such as adsorption, membrane separation, electrophoresis, chromatographic separation, and electroosmosis that are exercised for processing of dilute liquid streams.