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Microalgae for Removing Pharmaceutical Compounds from Wastewater
Published in Sreedevi Upadhyayula, Amita Chaudhary, Advanced Materials and Technologies for Wastewater Treatment, 2021
Eliana M. Jimenez-Bambague, Aura C. Ortiz-Escobar, Carlos A. Madera-Parra, Fiderman Machuca-Martinez
The fixation of micropollutants depends mainly on their physicochemical properties such as the octanol-water partition coefficient (log Kow), solid–water distribution coefficient (Kd), and acid dissociation constant (PKa) (Carballa et al. 2005). Log Kow is the affinity of a substance on the lipid fraction and determines the hydrophobicity (log Kow ≥ 3) and hydrophilicity (log Kow <3) of this substance. (The hydrophobic compounds are most effectively removed through sorption.) Pharmaceutical compounds that are more effective in removing their log Kow are above 4 (Matamoros et al. 2015). Non-polar compounds have a strong affinity to biosorbents due to hydrophobic interactions that can cross cell membranes and be absorbed into the organic matrix (Gadd 2009). Log Kd is determined by the ratio between the contaminant concentration and the amount of water in the soil. PKa defines the ionization level, the acceptance or the donation of protons under a pH value. Compounds with acid characteristics have better sorption.
Herbicides in the Environment
Published in Yeqiao Wang, Landscape and Land Capacity, 2020
Kim A. Anderson, Jennifer L. Schaeffer
In the environment, many herbicides are present in a charged state (not neutral). Charged species have different properties and reactivities as compared to their neutral counterparts. Therefore, the extent to which a compound forms ions in environmental ecosystems is important. The pKa is a measure of the strength of an acid relative to water. Strong organic acids (pKa ≅ 0–3) in ambient natural waters (pH 4–9) will be present predominantly as anions. Conversely, very weak acids (pKa ≥ 12) in ambient natural waters will be present in their associated form (neutral). In an analogous fashion, strong bases (pKa ≥ 11) will be present as ions.[5] Examples of weak acids are 2,4-D and triclopyr, and examples of weak bases are atrazine, dicamba, and simazine (Table 18.1).
Light-Driven Microfluidic Systems
Published in George K. Knopf, Kenji Uchino, Light Driven Micromachines, 2018
One type of pH-sensitive hydrogel that has incorporated in a variety of microsystems contains hydroxyethyl methacrylate-acrylic acid (HEMA-AA). This environmentally sensitive hydrogel undergoes abrupt volumetric changes when the pH of the surrounding medium increases slightly above the phase transition point pKa. Note that pKa is the negative of the base-10 logarithm of the acid dissociation constant (Ka) of a solution. If the networked gel is immersed in an ionic aqueous solution, then the polymer chains will absorb water and the association, dissociation, and binding of the various ions to the chains will cause the hydrogel material to swell producing a usable micro-force. The expansion and contraction of the hydrogel (Section 5.2) under environmental stimuli has been used to regulate the flow of liquids in a variety of microfluidic systems (Baldi et al. 2003; Liu et al. 2002a). The advantages of hydrogel over other smart material microactuator are relatively simple fabrication, no external power requirements, no integrated electronics, significant displacements (up to 185 μm), and relatively large force generation (~22 mN) (Al-Aribe and Knopf 2010).
Combined microfiltration and adsorption process applied to public water supply treatment: water quality influence on pesticides removal
Published in Environmental Technology, 2020
Alcione Aparecida de Almeida Alves, Giselle Louise de Oliveira Ruiz, Thyara Campos Martins Nonato, Catiane Pelissari, Adriana Dervanoski, Maurício Luiz Sens
The mean pH value (7.29) of the CSTW fortified with pesticides carbamates was lower than the value of pHZCP (7.49). For pH values of the solution lower than pHZCP there will be a positive charge on the surface of the adsorbent [34]. The carbamates studied are classified as acidic herbicides (pKa carbaryl = 10.4; pKa carbofuran = 12.28 and pKa methomyl = 13.27). The higher the value of pKa, the weaker the acidic strength [35]. Carbaryl is the carbamate that has the highest acid content, followed by carbofuran and methomyl. This may also explain the higher adsorption capacity and chemical affinity of this carbamate for the adsorbent surface studied. The higher the acidic strength, the greater the ability to form negatively charged ions. The removal of the carbamates can also be related to their adsorption on the surface of the GAC by dispersive iterations due to the small difference between the pH of the solution (7.29) and pHZCP (7.49). When the pH of the solution is less than pKa of the herbicide, concentration of the adsorbates in undissociated form will be greater than the dissociated or anionic form. Wibowo et al. [36] studied the influence of surface chemistry and pH of the solution on the adsorption of benzene and toluene on activated carbons treated with nitric acid and thermally with nitrogen flow. The adsorbent used was the commercial F-400 coal. The treatment with acid caused the introduction of a significant number of acid oxygenated surface groups on the surface of the adsorbent. In this case, dispersive iterations were predominant because of the attraction between the orbital over the basal carbon plane and the electron density in the aromatic ring of benzene and toluene (iterations ).
Emerging role of organic acids in leaching of valuable metals from refinery-spent hydroprocessing catalysts, and potential techno-economic challenges: A review
Published in Critical Reviews in Environmental Science and Technology, 2021
Ashish Pathak, Mari Vinoba, Richa Kothari
As protons are obtained from the dissociation of the acid, the higher strength acids are likely to provide greater H+ into the leaching media. Therefore, the strength of organic acid is an important criterion in selecting a particular organic acid for metal leaching. However, the strength of organic acids is generally based on several factors, such as the relative stability of the conjugate base of the acid and the corresponding pKa. The lower the pKa, the more strong acid (Theron & Lues, 2011).
Effect of brine type and pH on the interfacial tension behavior of carbonated brine/crude oil
Published in Journal of Dispersion Science and Technology, 2021
Saeed Zaker, Roohollah Parvizi, Ebrahim Ghaseminejad, Amin Moradi
In order to see the direct relationship of to pH in one equation, Ka is often presented as a logarithmic constant, pKa equal to