Optimization of anionic dye adsorption ontoMelia azedarachsawdust in aqueous solutions: effect of calcium cations

Study on the carbon source stability of constructed wetland prepared from modified aged straw

The low cost of biomass has made it an important option for providing carbon sources in the treatment of low carbon to nitrogen ratio (C/N) wastewater constructed wetland (CW). However, the unstable release of biomass carbon source reduces utilization and operation efficiency of CW. In this study, aged corn straw was used as raw material, and modification treatments with acid, alkali and oxidant were to optimize the conditions for stable carbon source release. The results showed that the modified straw exhibited three trends (stable release, continuous release, and short-term release) under water immersion conditions. The electrical conductivity (EC) of straw modified by HCl, H2SO4 and low-concentration KMnO4 (0.01 mol L-1) was low, so the supply of carbon sources in CW was obviously insufficient. The straw modified by HNO3 (1.5 or 2.5 mol L-1), KMnO4 (0.05 mol L-1), KMnO4 (0.05 mol L-1) + HCl (0.004 mol L-1) was continuously released chemical oxygen demand during the experiment, the increase in EC was significant, which could be used as an additional carbon source for CW. The research results will promote the improvement of biomass carbon source utilization in CW and improve the utilization value of straw.

Process and mechanism modeling of cefotaxime removal from hospital wastewater using pistachio shells based magnetic activated carbon nanoparticles

Antibiotic residues have been extensively identified in diverse aquatic environments, posing significant health risks to both humans and animals, while also presenting challenges to the environment. Consequently, the imperative need to effectively removal antibiotics from the environment has become a very importance issue. In this study, response surface methodology with central composite design was employed to systematically investigate the effects of key process parameters, on the removal of cefotaxime (CTX) from hospital wastewater using pistachio sells based activated carbon modified with FeCl3. The modified activated carbon was synthesized using a thermochemical method and characterized by analytical techniques including FE-SEM, FTIR, XRD, pHpzc, and BET analysis, which demonstrated its remarkable physicochemical properties. Maximum removal efficiency of 99.1% was obtained via the optimal values of 45 mg L- 1 of initial CTX concentration, solution pH 7, and 200 mg L- 1 of Fe@ACP dosage, 56 min of reaction time through adsorption process. According to the results, the non-linear Langmuir isotherm model (R2 = 0.9931) and non-linear second order kinetic model (R2 = 0.9934) are suitably described the monolayer and chemisorption of CTX adsorption. The maximum adsorption capacity of Fe@ACP is 651.6 mg g- 1. Consequently, the developed treatment process revealed successful performance for quick and efficient removal of CTX by Fe@ACP. The developed process introduced an economic and green approach for the comprehensive utilization of agricultural waste resources used for environmental pollution control.

Iron-modified activated carbon derived from agro-waste for enhanced dye removal from aqueous solutions

Background and aim

Finding a cost-effective adsorbent can be an obstacle to large-scale applications of adsorption. This study used an efficient activated carbon adsorbent based on agro-waste for dye removal.

Methods

Pistachio shells as abundant local agro-wastes were used to prepare activated carbon. Then, it was modified with iron to improve its characteristics. Acid red 14 was used as a model dye in various conditions of adsorption (AR14 concentration 20–150 mg L⁻¹, pH 3–10, adsorbent dosage 0.1–0.3 g L⁻¹, and contact time 5–60 min).

Results

A mesoporous adsorbent was prepared from pistachio shells with 811.57 m² g⁻¹ surface area and 0.654 cm³ g⁻¹ pore volume. Iron modification enhanced the characteristics of activated carbon (surface area by 33.3% and pore volume by 64.1%). Adsorption experiments showed the high effectiveness of iron-modified activated carbon for AR14 removal (>99%, >516 mg g⁻¹). The adsorption followed the pseudo-second kinetic model (k = 0.0005 g mg⁻¹ min⁻¹) and the Freundlich isotherm model (K_f = 152.87, n = 4.61). Besides, the reaction occurred spontaneously (ΔG⁰ = −36.65 to −41.12 kJ mol⁻¹) and was exothermic (ΔH⁰ = −41.86 kJ mol⁻¹ and ΔS⁰ = −3.34 J mol⁻¹ K⁻¹).

Conclusion

Iron-modified activated carbon derived from pistachio shells could be cost-effective for the treatment of industrial wastewater containing dyes.

Application of Cordia trichotoma sawdust as an effective biosorbent for removal of crystal violet from aqueous solution in batch system and fixed-bed column

In this work, for the first time, Cordia trichotoma sawdust, a residue derived from noble wood processing, was applied as an alternative biosorbent for the removal of crystal violet by discontinuous and continuous biosorption processes. The optimum conditions for biosorption of crystal violet were 7.5 pH and a biosorbent dosage of 0.8 g L^-1. The biosorption kinetics showed that the equilibrium was reached at 120 min, achieving a maximum biosorption capacity of 107 mg g^-1 for initial dye concentration of 200 mg L^-1. The Elovich model was the proper model for representing the biosorption kinetics. The isotherm assays showed that the rise of temperature causes an increase in the biosorption capacity of the crystal violet, with a maximum biosorption capacity of 129.77 mg g^-1 at 328 K. The Langmuir model was the most proper model for describing the behavior. The sign of ΔG⁰ indicates that the process was spontaneous and favorable, whereas the ΔH⁰ indicates an endothermic process. The treatment of the colored simulated effluent composed by dyes and salts resulted in 80% of color removal. The application of biosorbent in the fixed-bed system achieved a breakthrough time of 505 min, resulting in 83.35% of color removal. The Thomas and Yoon-Nelson models were able to describe the fixed-bed biosorption behavior. This collection of experimental evidence shows that the Cordia trichotoma sawdust can be applied for the removal of crystal violet and a mixture of other dyes that contain them.

A rapid and efficient removal approach for degradation of metformin in pharmaceutical wastewater using electro-Fenton process; optimization by response surface methodology

Presence of emerging contaminants such as pharmaceutical products in aquatic environments has received high concern due to their undesirable effect on wildlife and human health. Current work deals with developing a treatment model based on the electro- Fenton (EF) process for efficient removal of metformin (MET) from an aqueous medium. The obtained experimental results revealed that over the reaction time of 10 min and solution pH of 3, the maximum removal efficiency of 98.57% is achieved where the value of MET initial concentration, current density, and H₂O₂ dosage is set at 10 mg.L^-1, 6 mA.cm^-2, and 250 μL.L^-1, respectively, which is in satisfactory agreement with the predicted removal efficiency of 98.6% with the desirability of 0.99. The presence of radical scavengers throughout the mineralization of MET under the EF process revealed that the generation of ^•OH radicals, as the main oxidative species, controlled the degradation mechanism. The obtained kinetics data best fitted to the first order kinetic model with the rate constant of 0.4224 min^-1 (R² = 0.9940). The developed treatment process under response surface methodology (RSM) was employed for modeling the obtained experimental data and successfully applied for efficient removal of the MET contaminant from pharmaceutical wastewater as an adequate and cost-effective approach.

Comparison and Optimization of Reactive Dyes and Coating Performance on Fraxinus mandshurica Veneer

In this study, Fraxinus mandshurica veneer was dyed with reactive brilliant red X-3B, black KN-B and blue K-3R dyes. The dye concentration, bath ratio and dyeing time were selected for an orthogonal experiment. Analysis of variance showed that the dye concentration had the greatest effect on the dye uptake of F. mandshurica veneer. In the independent experiments, dye uptake increased at first and then decreased with increasing dye concentration; the chromatic aberration increased with the dye concentration and then remained steady. The infrared spectra were used to examine the dyeing behaviors before and after dyeing and the binding form between reactive dyes and F. mandshurica veneer was analyzed. Based on the optimization of process parameters, the optimal dyeing condition was considered to be 75 °C, the dye concentration to be 0.5–1.0%, the dyeing time to be 60 min and the bath ratio to be 20:1. The dye uptakes of reactive brilliant red X-3B, black KN-B and blue K-3R dyes were 75.0–75.4%, 50.0–64.6% and 32.0–66.0%, respectively. The chromatic aberration of F. mandshurica veneer dyed with reactive brilliant red X-3B, black KN-B and blue K-3R dyes was 53.0–59.0, which was a significant increase. After dyeing, the hardness and impact strength of the waterborne coating on the dyed F. mandshurica increased but adhesion was reduced. The coating films produced a matte glossiness.

Optimization of non-thermal plasma efficiency in the simultaneous elimination of benzene, toluene, ethyl-benzene, and xylene from polluted airstreams using response surface methodology

Treatment with a non-thermal plasma (NTP) is a new and effective technology applied recently for conversion of gases for air pollution control. This research was initiated to optimize the efficient application of the NTP process in benzene, toluene, ethyl-benzene, and xylene (BTEX) removal. The effects of four variables including temperature, initial BTEX concentration, voltage, and flow rate on the BTEX elimination efficiency were investigated using response surface methodology (RSM). The constructed model was evaluated by analysis of variance (ANOVA). The model goodness-of-fit and statistical significance was assessed using determination coefficients (R ² and R ²_adj) and the F-test. The results revealed that the R ² proportion was greater than 0.96 for BTEX removal efficiency. The statistical analysis demonstrated that the BTEX removal efficiency was significantly correlated with the temperature, BTEX concentration, voltage, and flow rate. Voltage was the most influential variable affecting the dependent variable as it exerted a significant effect (p < 0.0001) on the response variable. According to the achieved results, NTP can be applied as a progressive, cost-effective, and practical process for treatment of airstreams polluted with BTEX in conditions of low residence time and high concentrations of pollutants.