Direct red 81 adsorption on iron filings from aqueous solutions; kinetic and isotherm studies

Adsorption characteristics and applications of andesite in removing some pollutants from wastewater

Andesite was employed to effectively extract mercury(II) in an aqueous solution. After evaluating its characteristics, andesite was characterized by applying modern techniques such as BET and TGA methods. The study employed SEM and TEM measurements to analyze the variation in the surface shape and crystallinity of the metal due to adsorption. Using the EDX process, the chemical composition, weight, and atomic percentage of each element of andesite were determined. FTIR techniques were also used to confirm the TEM-EDX findings. Zeta potential was estimated. Cycles of regeneration and desorption have been examined. 99.03% was the highest uptake percentage. Adsorbent quantity (0.0025-0.05) g/L, contact time (5-60) min, pH (2-10), temperature (25-60) °C, and dose (0.0027, 0.0044, 0.0125, 0.0155, and 0.0399) mg/L all affect the amount of removal that increases with the increase in contact time, pH, dose, and temperature but drops as the metal ion concentration rises. The ideal values for contact time, pH, metal ion concentration, dose, and temperature were found to be, respectively, 30 min, 0.0155 mg/l, 0.02 g/l, and 40 °C. The calculation of thermodynamic parameters, including ΔH, ΔG, and ΔS, was imperative in establishing that the mechanism of heavy metal adsorption on andesite was endothermic, exhibiting a physical nature that escalated with temperature rise. The Freundlich adsorption equation's linear form is matched by the adsorption of mercury(II) on andesite; constant n was 1.85, 1.06, 1.1, and 1.1, whereas the Langmuir constant qm was found to be 1.85, 2.41, 3.54, and 2.28 mg/g at 25-60 °C. Furthermore, adsorption follows a pseudo-second-order rate constant of (3.08, 3.24, 3.24, and 13) g/mg/min under identical temperature conditions, as opposed to a first-order rate constant of 4, 3, 2.6, and 2. Hg2+, NH4+, Cl-, Br-, NO3-, SO42-, Na+, K+, H2S, and CH3SH were all extracted from wastewater by this application.

Photocatalytic degradation of 2,4-dichlorophenoxyacetic acid from aqueous solutions by Ag3PO4/TiO2 nanoparticles under visible light: kinetic and thermodynamic studies

Between the countless chemical substances applied in agriculture, 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide is considered as a toxic and carcinogenic pollutant which is difficult to remove from water due to its biological and chemical stability and high solubility. The goal of this study was photocatalytic degradation of 2,4-D, using Ag₃PO₄/TiO₂ nanoparticles under visible light. The Ag₃PO₄/TiO₂ nanoparticles were characterized using XRD, FESEM and EDS analysis to investigate its crystal structure and elemental compounds. The effect of operating parameters such as pH, contact time, catalyst dose, and initial concentration of herbicide on the efficiency of the process was studied. Increasing the pH and initial concentration of herbicide led to the reduction of the efficiency of removing the herbicide, while increasing contact time and catalyst dose increased the efficiency. The best result (98.4% removal efficiency) was achieved at pH = 3, 1 g/L catalyst dose, 60 min contact time, and 10 mg/L initial concentration of 2,4-D. According to the results, 2,4-D removal efficiency with Ag₃PO₄/TiO₂ photocatalyst reached 96.1% from 98.4% after 5 cycles of reaction. The pseudo-first-order kinetics was the best fit for the 2,4-D degradation by Ag₃PO₄/TiO₂ with correlation coefficients (R² = 0.9945). The results demonstrated that the photocatalytic process using Ag₃PO₄/TiO₂ nanoparticles in the presence of visible light had a relatively good efficiency in removing 2,4-D. Moreover, Ag₃PO₄/TiO₂ can be used as a reusable photocatalyst for the degradation of such toxins from polluted water and wastewater.

Removal of Acid Blue 62 textile dye from aqueous solutions by cerium reagents

The removal of Acid Blue 62 (AB62) dye which is known as a pollutant agent and contains in wastewater of textile industry has been studied in this work by using five various cerium compounds as the oxidizing agents. The parameters involved in the oxidation reaction such as pH, initial dye concentration and the oxidizing agent dosage have been investigated using both batch and semi-batch reactors at ambient temperature. The results indicated that the rate of oxidation for various cerium reagents is in the following order: CeF₄ > (NH₄)₂Ce (NO₃)₆> Ce (SO₄)₂ > CeCl₃ > Ce (CH₃COO)₃, where cerium fluoride (CeF₄) had the highest removal yields, 99.9% and 95%, for dye de-colouration and COD (chemical oxygen demand), respectively. The analysis of the dye removal was done by using UV-VIS spectrometry, GC-MS and HPLC methods which indicated the aromatic ring cleavage of AB62 dye by CeF₄. The half-life measurement was employed to evaluate the reaction rate model for decomposition of AB62 dye by CeF₄.

Process optimization for effective bio-decolourization of reactive orange 16 using chemometric methods

Azo group containing reactive dyes are most commonly used in textile and tannery industries due to its bright appearance and stable color. This study aims to investigate the decolourization of reactive orange 16 (RO16) dye by Pseudomonas aeruginosa 23N1 along with removal of chromate (Cr(VI)) and evaluation of optimal process condition. The regular two-level factorial design is used to screen out operational parameters and selects their levels for further optimization process through central composite design (CCD) based response surface methodology (RSM). The result revealed that glucose and peptone have a negative effect on the performance of dye decolourization. Bacteria exhibit high decolourization potential in yeast extract supplemented culture medium with no addition of external carbon sources. The percentages of decolourization obtained in model validated experiments are obtained as 95.0 ± 0.4% and 95.1 ± 0.5% for initial dye 50 mg/L and 150 mg/L, respectively, which exhibit satisfactory correlation with model predicted response. The simultaneous dye and Cr(VI) removal has been explored in this study. The decolourization of dye is only affected due to presence of high Cr(VI) concentration (>120 mg/L). Bacteria have shown satisfactorily decolourization for RO16 contaminated industrial wastewater. The strain 23N1 could be a good biological agent for decolourization of RO16 dye.