Heterogeneous degradation of amoxicillin in the presence of synthesized alginate-Fe beads catalyst by the electro-Fenton process using a graphite cathode recovered from used batteries.

Iron alginate beads (Fe-Alg) were prepared, characterized and implemented for the degradation of amoxicillin (AMX) by the heterogeneous electro-Fenton process using a graphite cathode recovered from used batteries. Scanning electron microscopy (SEM) showed that (Fe-Alg) beads have a spherical shape and the results of energy dispersive spectrometric (EDS) revealed the presence of iron in (Fe-Alg). Optimization of the operating parameters showed that a complete degradation of AMX was achieved within 90 min of heterogeneous electro-Fenton treatment by operating under these conditions: initial AMX concentration: 0.0136 mM, I = 600 mA, [Na2SO4] = 50 mM, pH = 3, T = 25 °C, ω = 360 rpm. The corresponding chemical oxygen demand (COD) abatement was 50%. Increasing the contact time increased the COD abatement to 85.71%, after 150 min of heterogeneous electro-Fenton treatment. The results of the kinetic study by using nonlinear methods demonstrated that the reaction of AMX degradation obeyed to a pseudo-second-order kinetic. Iron content of 4.63% w/w was determined by the acid digestion method. After 5 cycles of use, the Alg-Fe catalyst depletion was only 8%. Biodegradability was remarkably improved after electro-Fenton pretreatment, since it increased from 0.07 initially to 0.36. The heterogeneous electro-Fenton process had efficiently eliminated AMX and it increased the biodegradability of the treated solution.

Central composite design applied to paracetamol degradation by heat-activated peroxydisulfate oxidation process and its relevance as a pretreatment prior to a biological treatment.

In this study, the degradation of paracetamol (PCT) by thermo-activated peroxydisulfate (PDS) and the feasibility of coupling thermo-activated peroxydisulfate to activated sludge culture were examined. The effect of the relevant parameters on the thermo activated peroxydisulfate process, namely temperature, PDS concentration, initial pH and initial PCT concentration was investigated. As observed, the solution pH did not have a significant effect on the PCT degradation. The temperature increased the degradation of PCT, while an increase of the initial PCT concentration impacted negatively its degradation yield. The PDS concentration showed an optimal value of 8 mM. The operating parameters were then optimized by using a central composite design (CCD). After performing a screening of the various factors, response surface analysis led to the following optimal conditions for the yield of PCT degradation: 0.33, 5 mM, pH = 6 and 68°C for the initial PCT concentration, the initial peroxydisulfate concentration and the temperature respectively, leading to the removal of 94.2% of PCT. Under these conditions, the BOD5/COD ratio increased from 0.008 initially to 0.34 after 10 h. Showing a significant improvement of the biodegradability; consequently and even if the limit of biodegradability (0.4) was not achieved, a biological treatment could be promisingly considered.

Cotton textile waste valorization for removal of tetracycline and paracetamol alone and in mixtures from aqueous solutions: Effects of H3 PO4 as an oxidizing agent.

The use of waste and by-products locally available in large quantities and at low cost as adsorbents can be considered an appropriate approach for improving waste management and protecting the environment. Cotton textile waste was used to prepare adsorbents (MC) via pyrolysis followed by a chemical modification with H3 PO4 . MC samples were characterized by scanning electron microscopy, FTIR spectroscopy, and N2 adsorption-desorption isotherm. The results revealed that MC treated with 1 M H3 PO4 (MC1 ) showed an excellent adsorption performance. The single and binary adsorption of tetracycline (TC) and paracetamol (Pa) onto MC1 were studied. In a single system, TC was better adsorbed than Pa and maximum adsorption capacities qm are 87.7 mg/g and 62 mg/g, respectively. The adsorption follows the Langmuir and pseudo-second-order kinetic models. For a binary system, the experimental data indicate that Pa (44.04 mg/g) is better adsorbed than TC (24.13 mg/g). Adsorption equilibrium data of TC and Pa evaluated by the selectivity extended-Langmuir model in which selectivity factor was introduced provided good correlation results with the binary adsorption data. Cotton textile waste is potentially promising for the preparation of effective adsorbents for the removal of pharmaceutical residues in aqueous solutions. PRACTITIONER POINTS: Valorization of cotton textile waste into adsorbents. Adsorbents were prepared by pyrolysis at 600°C followed by chemical modification in the presence of H3 PO4 . Removal of tetracycline (TC) and paracetamol (Pa) alone or in mixtures by adsorption. Adsorbent showed high-capacity adsorption of the TC and Pa even in a mixture from solutions at low concentrations. The Langmuir and selectivity extended-Langmuir models describe the adsorption of TC and Pa alone and in mixtures, respectively.

Paracetamol degradation by photo-activated peroxydisulfate process (UV/PDS): kinetic study and optimization using central composite design.

In this study, peroxydisulfate (PDS) was successfully activated by UV-irradiation for the degradation of paracetamol (PCT) frequently detected in the environment. Results showed that increasing the initial PDS concentration from 5 to 20 mM promote the removal of PCT from 49.3% to 97.5% after 240 min of reaction time. As the initial PCT concentration increased from 0.066 to 0.132 mM, the degradation efficiency of PCT decreased from 98% to 73% after 240 min of reaction time, while the optimal pH was found to be 6. It is apparent that the degradation rate of PCT was favored by the lamp power regardless of the initial PCT concentration, for 0.132 mM of PCT, the degradation efficiency increased from 73% to 95% when the lamp power increased from 9 to 30 W, respectively. The kinetic of degradation of the PCT was described by a pseudo-second order kinetic model. The model obtained by central composite design led to the following optimal conditions for PCT degradation: 0.132 mM initial PCT concentration, 20 mM PDS dose, pH solution 6 and lamp power 30 W led to the removal of 92% of PCT at 25 °C within 240 min of reaction time.

Tetracycline hydrochloride degradation by heterogeneous photocatalysis using TiO2(P25) immobilized in biopolymer (chitosan) under UV irradiation.

TiO2(P25) has been widely used to treat wastewater; however, the elimination of TiO2(P25) suspended in the treated water causes running costs and induces secondary pollution, which greatly restricts its practical applications. Consequently, several methods have been implemented to immobilize TiO2(P25) on various substrates. This work deals with the immobilization of TiO2(P25) in chitosan film by using the cross-linking method. The prepared catalyst was characterized using X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), UV-Vis diffuse reflectance spectra (DRS) and scanning electron microscopy (SEM), and its catalytic activity in tetracycline hydrochloride (TC) degradation under UV light was explored. XRD, FTIR, DRS and SEM characterization indicated that TiO2(P25) was successfully immobilized on chitosan film, the chemical structure of TiO2(P25) did not change after the immobilization and the TiO2(P25) was uniformly dispersed in the composite. Chitosan/TiO2(P25) was used for the removal of TC by photocatalysis under UV irradiation. The effects of operational parameters such as amount of TiO2(P25), agitation speed and the initial TC concentration were investigated. An 87% removal efficiency of TC was obtained with 0.12 g of TiO2(P25) and TC removal was significantly enhanced by the agitation of the solution. The TC removal efficiency decreased from 72 to 44% when TC concentration increased from 30 to 40 mg/L after 60 min reaction time, the photocatalytic reactions followed the pseudo-second-order kinetic.

Agar-agar impregnated on porous activated carbon as a new adsorbent for Pb(II) removal.

This paper presents a new sorbent, agar-agar (AA), impregnated on porous activated carbon (AC) - and its Pb(II) sorption properties. The influence of impregnation ratio (AA/AC) on the Pb(II) ion sorption properties is studied in order to optimize this parameter. The developed AC-AA shows substantial capability to sorb Pb(II) ions from aqueous solutions and 75% represents the optimal impregnation ratio. The AC-AA sorbent with impregnation ratio of 75% was characterized by a liquid displacement method, point of zero charge pH (pHPZC), scanning electron microscopy and Fourier transform infrared spectroscopy. The effect of parameters such as sorbent dosage, pH, agitation time and initial Pb(II) concentration on Pb(II) removal were examined. In addition, sorption kinetics and sorption isotherms were determined. The maximum uptake of Pb(II) was about 242 mg/g at 25 °C, pH 5 and initial Pb(II) concentration of 100 mg/L. The kinetic data were fitted to the models of pseudo-first-order and pseudo-second-order, and the experimental results follow closely the pseudo-second-order model. The results also reveal that the experimental equilibrium is very close to those predicted by the Freundlich model. The developed AC-AA exhibits high Pb(II) sorption capacity, offering possibilities for future practical use.

Combination of the Electro/Fe3+/peroxydisulfate (PDS) process with activated sludge culture for the degradation of sulfamethazine.

In this paper, the major factors affecting the degradation and the mineralization of sulfamethazine by Electro/Fe3+/peroxydisulfate (PDS) process (e.g. current density, PDS concentration, Fe3+ ions concentration and initial sulfamethazine (SMT) concentration) were evaluated. The relevance of this process as a pretreatment prior to activated sludge culture was also examined. Regarding the impact on SMT degradation and mineralization, the obtained results showed that they were significantly enhanced by increasing the current density and the PDS concentrations in the ranges 1-40mAcm-2 and from 1 to 10mM respectively; while they were negatively impacted by an increase of the initial SMT concentration and the Fe3+ concentration, from 0.18 to 0.36mM and from 1 to 4mM respectively. The optimal operating conditions were therefore 40mAcm-2 current density, 10mM PDS concentrations, 1mM Fe3+, and 0.18mM SMT. Indeed, under these conditions the degradation of SMT and its mineralization yield were 100% and 83% within 20min and 180min respectively. To ensure a significant residual organic content for activated sludge culture after Electro/Fe3+/PDS pre-treatment, the biodegradability test and the biological treatment were performed on a solution electrolyzed at 40mAcm-2, 10mM PDS concentrations, 1mM Fe3+, and 0.36mM SMT. Under these conditions the BOD5/COD ratio increased from 0.07 to 0.41 within 6h of electrolysis time. The subsequent biological treatment increased the mineralization yield to 86% after 30days, confirming the relevance of the proposed combined process.

The electro/Fe3+/peroxydisulfate (PDS) process coupled to activated sludge culture for the degradation of tetracycline.

The removal of tetracycline (TC) by electro/Fe3+/peroxydisulfate process combined to the biological treatment is reported in this study. Effect of current density, peroxydisulfate (PDS) concentration, Fe3+ ions concentration and initial tetracycline concentration were investigated. The results indicated that the removal efficiency of TC increased with increasing current density and decreases with tetracycline initial concentration. This effect is attributed to the competition of TC and electrogenerated intermediate compounds for the consumption of oxidizing SO4- radicals. The TC degradation efficiency was improved significantly when the PDS and Fe3+ concentrations increased from 1 to 10 mM and 1-2 mM, respectively. Above 10 mM PDS and 2 mM Fe3+ concentrations, a decrease of TC degradation efficiency was observed. The optimal operating conditions were: 2 mM Fe3+, 0.06 mM TC, 10 mM PDS concentrations and 40 mA cm-2 current density. Under these conditions a total degradation of TC within only 40 min of reaction time and 98% of mineralization yield after 3 h electrolysis were obtained. The biodegradability of the solution after electro/Fe3+/peroxydisulfate pre-treatment showed that BOD5/COD ratio increased from 0.00 initially to 0.42, 0.46 and 0.83 after 4 h, 5 h and 6 h, respectively, namely above the limit of biodegradability (0.4). The enhancement of biodegradability initially from 0.00 to 0.42 and 0.46 after 4 h and 5 h of electrolysis respectively, was confirmed by the biological treatment, since 77.51% and 92.54% of the dissolved organic carbon was removed respectively by coupling Electro/Fe3 +/PDS pre-treatment and a biological treatment.

Removal of a mixture tetracycline-tylosin from water based on anodic oxidation on a glassy carbon electrode coupled to activated sludge.

The purpose of this study was first to examine the electrochemical oxidation of two antibiotics, tetracycline (TC) and tylosin (Tylo), considered separately or in mixture, on a glassy carbon electrode in aqueous solutions; and then to assess the relevance of such electrochemical process as a pre-treatment prior to a biological treatment (activated sludge) for the removal of these antibiotics. The influence of the working potential and the initial concentration of TC and Tylo on the electrochemical pre-treatment process was also investigated. It was noticed that antibiotics degradation was favoured at high potential (2.4 V/ saturated calomel electrode (SCE)), achieving total degradation after 50 min for TC and 40 min for Tylo for 50 mg L(-1) initial concentration, with a higher mineralization efficiency in the case of TC. The biological oxygen demand in 5 days (BOD5)/Chemical oxygen demand (COD) ratio increased substantially, from 0.033 to 0.39 and from 0.038 to 0.50 for TC and Tylo, respectively. Regarding the mixture (TC and Tylo), the mineralization yield increased from 10.6% to 30.0% within 60 min of reaction time when the potential increased from 1.5 to 2.4 V/SCE and the BOD5/COD ratio increased substantially from 0.010 initially to 0.29 after 6 h of electrochemical pre-treatment. A biological treatment was, therefore, performed aerobically during 30 days, leading to an overall decrease of 72% of the dissolved organic carbon by means of the combined process.