Adsorptive removal of arsenic from drinking water using KOH-modified sewage sludge-derived biochar

© 2024 The Authors. Published by Elsevier B.V. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.clwat.2024.100022This paper reveals a green chemistry approach to remove arsenic (As+3) from water using potassium hydroxide (KOH) modified sewage sludge-derived biochar (SSDB-KOH). Characterisation of the morphology, particle size and composition of the SSDB-KOH pre- and post-adsorption confirmed porous and heterogenous surface favouring adsorption. At ambient temperature (20 °C), the SSDB-KOH dose of 20 g/l achieved 98 % arsenite removal at nearly neutral solution pH (8). This compared favourably with pristine SSDB, where the performance was limited to 41.6 % removal. The enhanced arsenite adsorption of SSDB-KOH was informed by several mechanisms, including ionic interactions, pore filling and metal-pi interactions. The experimental data fits closely with the Langmuir isotherm and pseudo-second-order kinetic models, revealing monolayer adsorption and the chemical interaction between adsorbents and the adsorbate. The spontaneous and endothermic nature of the process was confirmed by the negative value of ΔG and the positive value of ΔH, respectively. The performance of the biochar was evaluated for four-cycle regeneration. Finally, a cost analysis was performed to demonstrate the economic feasibility of using SSDB-KOH to remove arsenic from water.Accepted versio

Extraction-Resistant Composition Containing Activated Charcoal for Deterring Opioid Drugs Abuse.

Objective: Examine the resistance efficiency of activated charcoal against opioid drugs extraction in different aqueous solutions. Background: Activated charcoal is a porous material with large surface area and high capacity for adsorbing different molecules. In this study, we evaluated the efficiency of charcoal in adsorbing dextromethorphan HBr (DEX) in different aqueous solutions, minimizing the amount of the drug that could be extracted for abuse by injection. Methods: In 1:8 weight ratio, DEX and charcoal were mixed in 10 mL aqueous extracting solvents, most commonly used by abusers. The samples were centrifuged at 1500 rpm for 5 min. The supernatant was separated from the sediment and analyzed by UV-Vis spectroscopy (276 nm) to determine the % of the drug extracted by the different solvents. The sediment was analyzed by DSC (heating from 25 to 350 °C @ 10 °C/min.) to confirm the drug adsorption on the charcoal. Results: Drug extraction varied across the different solvents. Minimal drug extraction (\u3c 20%) was achieved in water, 0.1% sodium bicarbonate, and saline solutions. Modest extraction (~ 25%) was achieved in 0.83 M acetic acid, and the highest drug extraction (~ 60%) was achieved in 40% ethanol. The DSC thermograms confirmed the adsorption of the drug on the charcoal particles. Conclusion: Activated charcoal-based compositions could effectively reduce opioid drugs extraction in most of the extracting solvents. Further work is required to improve the deterrence efficiency of such compositions in the hydroalcoholic solutions. Grants: NSU Grant 335081

Impact of Drug Nature and Solvent Type on Charcoal Adsorption Efficiency

Objective: Investigate the effects of the ionic nature of the drug and the type of solvent on the adsorption efficiency of charcoal. Background: Activated charcoal is widely used as a detoxifying agent for its efficient adsorption of various molecules. In this study, we evaluated the effect of the drug ionic nature and the effect of solvent type on the charcoal’s adsorption efficiency. Methods: Cationic dextromethorphan HBr, anionic diclofenac sodium, and non-ionic acetaminophen were separately mixed with charcoal (1:8 ratio) in 10 mL different solvents. The samples were centrifuged, and the supernatant was analyzed for drug content (UV-Vis spectroscopy). The % of the adsorbed drug was calculated from mass balance. The sediment was analyzed (DSC, 25–350 °C @ 10 °C/min.) to confirm the drug adsorption onto charcoal. Results: \u3e90% drug adsorption in HCl. The results in the other solvents varied among the drug molecules. For dextromethorphan, \u3e90% adsorption in saline and NaHCO3, ~70–80% in water and vinegar, and ~40% in 40% ethanol. For diclofenac, \u3e90% adsorption in water and vinegar, ~70% in ethanol and saline, and minimal adsorption (6%) in NaHCO3. For acetaminophen, \u3e90% adsorption in water, ethanol, and NaHCO3, ~80% in vinegar, and ~40% in saline. The DSC results confirmed the drugs’ adsorption on the charcoal. Conclusion: Charcoal has in general an effective adsorption capacity in water and acidic solutions for all drugs regardless of their nature. The charcoal adsorption capacity in other solvents is affected by other drug properties (e.g., lipophilicity). Grants: NSU Grant 335081

Batch adsorption study of Congo Red dye using unmodified Azadirachta indica leaves: isotherms and kinetics

A low-cost adsorbent developed from unmodified Azadirachta indica leaves was used for adsorptive removal of the Congo Red dye from an aqueous medium. The adsorbent was characterized by the Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM) techniques. For optimization of operational parameters such as dye concentration, solution pH, adsorbent dose, contact time, and temperature, batch adsorption experiments were performed. It was found that for neem leaves powder (NLP), the optimum conditions were as follows: adsorbent dose of 0.8 g, contact time of 100 min having a solution with pH value of 5, adsorbate initial concentration of 40 ppm at temperature 60 °C where maximum amount of dye, i.e., 84%, removal was observed. The process followed pseudo-first-order kinetics, which reveals physical adsorption. According to isothermal investigations, sorption data were best fit with the Freundlich isotherm model. Thermodynamically, the adsorption of the Congo Red dye by the neem leaf powder was exothermic. Furthermore, the mechanistic removal of the Congo Red dye by the NLP has been explored with the help of the surface complex formation (PHREEQC) mechanism. Overall, the results of the study explore the promising nature of NLP for Congo Red dye removal. HIGHLIGHTS Providing clean water to the population is one of humanity's main challenges.; Adsorption is one of the most cost-effective and promising techniques for dye removal from polluted water.; 84% of Congo Red dye removal takes place at optimized conditions.; Isotherm, kinetic, and thermodynamics were studied.; The promising nature of the developed system was checked with tap water.