Fixed-bed adsorption of atrazine onto microwave irradiated Aegle marmelos Correa fruit shell: Statistical optimization, process design and breakthrough modeling

Degradation of Residual Herbicide Atrazine in Agri-Food and Washing Water

Atrazine, an herbicide used to control grassy and broadleaf weed, has become an essential part of agricultural crop protection tools. It is widely sprayed on corn, sorghum and sugar cane, with the attendant problems of its residues in agri-food and washing water. If ingested into humans, this residual atrazine can cause reproductive harm, developmental toxicity and carcinogenicity. It is therefore important to find clean and economical degradation processes for atrazine. In recent years, many physical, chemical and biological methods have been proposed to remove atrazine from the aquatic environment. This review introduces the research works of atrazine degradation in aqueous solutions by method classification. These methods are then compared by their advantages, disadvantages, and different degradation pathways of atrazine. Moreover, the existing toxicological experimental data for atrazine and its metabolites are summarized. Finally, the review concludes with directions for future research and major challenges to be addressed.

Adsorption mechanisms of atrazine isolated and mixed with glyphosate formulations in soil

In Brazil, the atrazine has been applied frequently to join with glyphosate to control resistant biotypes and weed tolerant species to glyphosate. However, there are no studies about atrazine's behavior in soil when applied in admixture with glyphosate. Knowledge of atrazine's sorption and desorption mixed with glyphosate is necessary because the lower sorption and higher desorption may increase the leaching and runoff of pesticides, reaching groundwaters and rivers. Thereby, the objective of this study was to evaluate the adsorption mechanisms of atrazine when isolated and mixed with glyphosate formulations in a Red-Yellow Latosol. The maximum adsorbed amount of atrazine in equilibrium (qe) was not altered due to glyphosate formulations. The time to reach equilibrium was shortest when atrazine was mixed with the Roundup Ready® (te = 4.3 hours) due to the higher adsorption velocity (k2 = 2.3 mg min-1) in the soil. The highest sorption of atrazine occurred when mixed with the Roundup WG®, with the Freundlich sorption coefficient (Kf) equal to 2.51 and 2.43 for both formulation concentrations. However, other glyphosate formulations did not affect the sorption of atrazine. The desorption of atrazine was high for all treatments, with values close to 80% of the initial adsorbed amount, without differences among isolated and mixed treatments. The change in the velocity and capacity of sorption for the atrazine mixed with some glyphosate formulations indicates that further studies should be conducted to identify the mechanisms involved in this process.

Comparative and Equilibrium Studies on Anionic and Cationic Dyes Removal by Nano-Alumina-Doped Catechol Formaldehyde Composite

Nano-alumina-doped catechol formaldehyde polymeric composite was prepared, characterized, and applied as an adsorbent for the removal of an anionic dye Congo red (CR) and a cationic dye SafraninO (SF), by adsorption process especially from aqueous solutions. Characterizations such as particle size distribution, zeta potential, BET, FTIR, and FESEM-EDAX were carried out for the adsorbent prepared. All experiments were conducted at the batch condition to study the effects of initial dye concentration (CR: 30–90 mg/L and SF: 10–50 mg/L), pH (2–11), temperature (25–55°C), and adsorbent dosage (0.05–0.3 g) on dye removal. The isotherm models (Langmuir, Freundlich, and Temkin) were analyzed for this adsorption work. The kinetic data obtained were analyzed by the pseudo-first-order, pseudo-second-order, Bangham, and Chien–Clayton equations. Dyes adsorption data were well fitted with the Freundlich isotherm equilibrium model and the pseudo-second-order kinetic model. Study results suggested that the nano-alumina-polymeric composite could be an effective adsorbent for anionic dye rather than cationic dye.

Removal of emerging pharmaceutical contaminants by adsorption in a fixed-bed column: A review

Pharmaceutical pollutants substantially affect the environment; thus, their treatments have been the focus of many studies. In this article, the fixed-bed adsorption of pharmaceuticals on various adsorbents was reviewed. The experimental breakthrough curves of these pollutants under various flow rates, inlet concentrations, and bed heights were examined. Fixed-bed data in terms of saturation uptakes, breakthrough time, and the length of the mass transfer zone were included. The three most popular breakthrough models, namely, Adams-Bohart, Thomas, and Yoon-Nelson, were also reviewed for the correlation of breakthrough curve data along with the evaluation of model parameters. Compared with the Adams-Bohart model, the Thomas and Yoon-Nelson more effectively predicted the breakthrough data for the studied pollutants.