Advanced oxidation of 4-chlorophenol via combined pulsed light and sulfate radicals methods: Effect of co-existing anions.

Pulsed light (PL) technology, which is based on photonic technology involves the application of broadband emission of light with short and high-power pulses is beginning to emerge for the treatment of wastes via advanced oxidation processes (AOP). The present work investigates the efficiency of PL as a light source for persulfate (PS) activation (PL/PS) and 4-chlorophenol)4-CP) degradation, an organic model pollutant. The influencing parameters on 4-CP degradation such as solution pH, reaction time, initial concentration of 4-CP, PS dose, pulse intensity and frequency, and distance from PL source are systematically investigated. With increasing pH from 3 to 9, the 4-CP degradation decreased from 49.79 ± 2.49 to 33.12 ± 1.66%. The 4-CP degradation followed the first order kinetics that was improved with increasing reaction time, PS dose, pulse intensity, frequency of pulse, and decreasing pH, initial 4-CP concentration and distance from the PL source. The presence of sulfate, chloride, and carbonate anions in the solution has the inhibitory effects on 4-CP degradation, while nitrate anion improved the performance of PL/PS system. In addition, presence of humic acid had an inhibitory effect on the PL/PS system, which led to a decrease of reaction rate constant and 4-CP degradation was performed in PL/PS system with OH, SO4-, O2- and 1O2 radicals. The contributions of OH and SO4- radicals were 46% and 51%, respectively for the 4-CP degradation and synergistic effect of PL/PS system showed a significant influence on 4-CP degradation while using a combination of PL and PS, suggesting that PL is an effective activator of PS.

Enhanced removal of humic acid from aqueous solution by combined alternating current electrocoagulation and sulfate radical.

Application of alternating current in electrocoagulation and activation of persulfate (AEC-PS) for the effective removal of humic acid (HA) from aqueous solution was evaluated. In order to optimize the removal efficiency HA by the AEC-PS process, several influencing parameters such as pH, reaction time, PS dose, current density (CD), concentration of NaCl, initial concentration of HA, and coexisting cations and anions influence were investigated. From the batch experiments, the highest HA removal efficiency obtained was 99.4 ± 0.5% at pH of 5, reaction time of 25 min, CD of 4.5 mA/cm2, PS dose of 200 mg/L, and NaCl concentration of 0.75 g/L for an initial HA concentration of 30 mg/L. When CD increased from 1.25 to 4.5 mA/cm2, the HA removal efficiency was improved from 88.8 ± 4.4% to 96.1 ± 1.5%. In addition, the type of coexisting cations and anions exerted a significant role, leading to a reduction in the removal efficiency of HA. To investigate the dominant free activated radical, radical scavengers such as tert-butyl alcohol and ethanol were employed. It was observed that both OH and SO4- radicals substantially contributed to the removal of HA, and the contribution of SO4- radical was higher than that of OH radical, suggesting that AEC-PS process could serve as a novel and effective treatment technique for the removal of organic matters from aqueous sources.

Fabrication of activated carbon from pomegranate husk by dual consecutive chemical activation for 4-chlorophenol adsorption.

In the present work, the fabrication of activated carbon (AC) from pomegranate husk (PHAC) by dual consecutive activation processes with ZnCl2 and NaOH as a chemical agent was studied. After that, the synthesized PHAC was used for adsorption of 4-chlorophenol (4CP) as a highly toxic compound for the human health and the environment. Different analytical techniques characterized the synthesized PHAC using ZnCl2/NaOH. The isotherms of N2 adsorption and desorption showed that total pore volume (Vtotal) and specific surface area (SBET) of PHAC were 0.404 cm3/g and 811.12 m2/g, respectively. The 4CP adsorption by PHAC studies revealed that the highest 4CP removal efficiency was 100% and obtained at 50, 100, and 150 mg/L of 4CP concentration with 2.5 g/L of PHAC. Based on the batch experiments, the highest 4CP removal was achieved at pH 6, 2.5 g/L of PHAC, and contact time of 60 min. The 4CP adsorption data of equilibrium and kinetics were successfully fitted to Langmuir's isotherm and Avrami fractional order.

Adsorption of 4-chlorophenol by magnetized activated carbon from pomegranate husk using dual stage chemical activation.

Separation under the influence of magnetic field has been widely explored to tackle environmental issues related to centrifuging and filtration. In this work, activated carbon produced from pomegranate husk (PHAC) using dual stage chemical activation was magnetized with iron salts and used for adsorption of 4-chlorophenol (4CP) from the synthetic wastewater. Adsorption experiments were conducted in batch mode to determine the removal efficiency of magnetized activated carbon pomegranate husk (MPHAC) as a function of initial 4CP concentration, solution pH, MPHAC dose, contact time, ionic strength, and temperature. The rough surface of MPHAC containing pores on the surface had a total pore volume of 0.623 cm3/g with a surface area of 1168 m2/g. The 4CP adsorption was highly dependent on ionic strength, solution pH, and temperature; the equilibrium was reached in 60 min of contact time. Kinetic models and equilibrium isotherms were employed to assess the fitness of adsorption data; results were fitted best with the Liu model giving maximum adsorption capacities of 446.89 ± 20.75 and 183.64 ± 17.85 mg/g for 1 and 2 g/L of MPHAC, respectively. For the investigation of the adsorption kinetics, Avrami fractionary-order model showed the best fit of the experimental data compared to other kinetic models.

Retention of atenolol from single and binary aqueous solutions by thin film composite nanofiltration membrane: Transport modeling and pore radius estimation.

The performance of a polyamide-based thin-film composite nanofiltration (NF) membrane (NF33) was investigated for the retention of atenolol, a pharmaceutical pollutant, from the single and binary aqueous solutions. The effect of pH, applied pressure, feed flux, initial atenolol (ATN) concentration, and different co-existing salts with varying concentrations were studied to test the performance of the membrane. The removal efficiency of ATN increased with increasing solution pH giving the highest retention (70.9 ± 3.1) at pH 9, which was slightly decreased with the increasing initial ATN concentration but increased with increasing applied pressure and feed flux. As per the uncharged solutes rejection concept, the average pore radius of NF membrane for slit-like and cylindrical pore geometries were, respectively 0.169 ± 0.003 and 0.264 ± 0.009 nm. The Spiegler-Kedem model could predict the performance of NF membrane by retaining ATN over the investigated range of feed flux. The calculated reflection coefficient (σ) was close to unity, demonstrating the convective transport. Addition of CaCl2 as a co-existing salt into the feed showed promoting effect on ATN retention, and its efficiency was lowered by the addition of NaCl and Na2SO4 salts. As per the cost analysis, the total annualized cost of treatment by the NF was found to be 0.53 $/m3.

Synergistic degradation of 4-chlorophenol by persulfate and oxalic acid mixture with heterogeneous Fenton like system for wastewater treatment: Adaptive neuro-fuzzy inference systems modeling.

The 4-chlorophenol (4-CP) is known to be a highly toxic compound having harmful effects on human health and the environment. Due to adverse effect of 4-CP, a new combination of persulfate (PS) and oxalic acid (OA) with heterogeneous Fenton like (HFL) system was developed and applied for 4-CP degradation as an emerging contaminant from synthetic wastewater. The individual (OA, PS, and HFL) and combined (HFL/OA, HFL/PS, and HFL/OA/PS) systems were investigated under various conditions to synergistic effects verification and determination of degradation mechanism of 4-CP. Compared to individual and combined systems, significant synergetic of 4-CP degradation efficiency was observed by HFL/OA/PS system. The highest 4-CP degradation efficiency by HFL/OA/PS system under optimal conditions (solution pH: 6, H2O2 dose: 275 mg/L, goethite dose: 125 mg/L, OA dose: 50 mg/L and PS dose: 100 mg/L) with an initial 4-CP concentration of 30 mg/L was 99.6 ± 4.9% after 35 min reaction time. 4-CP degradation by HFL/OA/PS system was followed with the first-order kinetic. The application of radical scavengers including ethanol (EtOH) and tert-butyl alcohol (TBA) revealed that the SO4•- radical was determined as primary produced radical species. The Cl- ions release was measured during degradation reaction at various 4-CP concentrations and indicating the complete 4-CP degradation. The developing of the adaptive neuro-fuzzy inference system (ANFIS) for 4-CP degradation efficiency prediction was revealed. These results show that prediction of 4-CP degradation efficiency using HFL/OA/PS system is possible by the ANFIS model with a high accuracy (R2: 0.98).