Degradation of tetracycline in aqueous media by ozonation in an internal loop-lift reactor

Batch Experimental Studies and Statistical Modeling for the Effective Removal of Tetracycline from Wastewater Using Bimetallic Zn-Cu-Metal-Organic Framework@Hydrogel Composite Beads

Antimicrobial resistance (AMR) is on an upsurge as more and more broad-spectrum antibiotics are being used haphazardly, resulting in imbalances in the ecosystem and disrupting common/systematic clinical protocols. To combat this issue, metal-organic framework embedded zinc-copper-benzenedicarboxylate@calcium alginate composite beads (Zn-Cu-BDC@CA CBs) were synthesized and utilized for the adsorption of tetracycline (TC) from water. The surface morphology, presence of functional groups, surface area, and thermal stability of Zn-Cu-BDC@CA CBs were evaluated by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and thermal gravimetric analysis (TGA), respectively. Batch adsorption experiments were also carried out to optimize the adsorption performance of Zn-Cu-BDC@CA CBs for TC by adjusting the key parameters, including pH of the solution, contact time, adsorbent dosage, temperature, and initial concentration of TC. From the RSM model, 96.8% removal of TC takes place under the optimum conditions (pH = 7.3, mass = 17.2 mg, concentration = 21.3 ppm, time = 3.4 h, and temperature = 31.8 °C), which aligns closely with the experimental batch study, where the addition of 20 mg of adsorbent to a 20 mL TC solution (20 mg/L) at a pH of 7 and a temperature of 27 °C yielded an impressive TC removal efficiency of 96.55% within 180 min. Zn-Cu-BDC@CA CBs possess homogeneous adsorption surfaces, and TC is adsorbed via monolayer chemisorption, according to the results derived from the Langmuir isotherm model and pseudo-second-order kinetic model. The thermodynamic analysis indicated that the adsorption process is both endothermic and spontaneous. In their entirety, the synthesized Zn-Cu-BDC@CA CBs exhibit certain operational advantages, such as simple separation, satisfactory adsorption performance, and decent recyclability, indicating their viability for industrial application of elimination of TC residues from aquatic environments.

Study on the degradation of tetracycline in wastewater by micro-nano bubbles activated hydrogen peroxide

Recently, the micro-nano bubble (MB) technology has attracted people's attention due to its special advantages. Here, we carried out the technology of combining MB and hydrogen peroxide (MB/H₂O₂) to achieve efficient degradation of tetracycline wastewater. The effect of MB/H₂O₂ technology on the degradation efficiency of tetracycline was deeply analysed by investigating the reaction time, H₂O₂ dosage, pH and MB inlet flow. The results showed that the degradation rate of tetracycline hydrochloride by MB/H₂O₂ technology can reach 92.43%, which is 9.44 and 3.94 times that of MB and H₂O₂ alone. Through electron spin resonance (ESR) analysis and free radical quenching experiments, a possible mechanism for MB/H₂O₂ technology to efficiently degrade TC was proposed. In the MB/H₂O₂ system, the high temperature and high pressure environment generated when MB ruptures can activate H₂O₂ to obtain a higher number of active oxygen species. •OH is the main reactive oxygen radical in the process of MB/H₂O₂ degradation of TC, followed by HO₂•/•O₂-. In addition, the possible intermediate products of the oxidation TC process were identified by HPLC-MS technology. Under the action of •OH and HO₂•/•O₂- free radicals, TC molecules undergo demethylation and hydroxylation, ring-opening reactions, isomerization, deethylation, deacylation, deamination and dehydration reactions to generate intermediate products and finally convert them into CO₂ and H₂O. The development of MB/H₂O₂ technology can potentially be used to efficiently remove TC substances in the water environment and provide a new method for water purification.

Cefotaxime removal enhancement via bio-nanophotocatalyst α-Fe2O3 using photocatalytic degradation technique and its echo-biomedical applications

The present paper evaluates the photocatalytic degradation (PCD) performance of the biofabricated hematite nanoparticles (α-HNPs) for the degradation approach of the Cefotaxime (Cfm). The optimum pH of the solution to achieve the best PCD was found to be 10.5. The kinetics study for the PCD of the Cfm via α-HNPs has been investigated and the reaction was found to be fellow pseudo-first-order at R² = 0.992. The mass loading impact of α-HNPs was investigated and estimated for the maximum degradation of Cfm 0.4 mg/mL. UV–Vis confirmed that α-HNPs had a direct transition bandgap at 3.78 eV at a maximum absorption wavelength of 362 nm with suspension stability for 7 days. The probable mechanism of the Cfm PCD via α-HNPs and the degradation pathway was conducted. The validation of the suspension stability of the α-HNPs (−68.6 ± 11.8 mV) was determined using the zeta potential investigation test. XRD investigation was conducted after Cfm PCD showing an average crystallite size of 27.0 nm. XRD, TEM, SEM, EDX, and FT-IR analyses have been conducted for the α-HNPs before and after Cfm PCD confirming the high efficiency for the reusability of the current biocatalyst α-HNPs for further use. TEM results of the particle sizes of α-HNPs were found at 19.2 ± 4.4 and 20.6 ± 7.4 nm respectively before and after Cfm PCD. The efficiency of the Cfm PCD was found to be 99.1% after 6 h. High potent as an antibacterial agent of α-HNPs was investigated either α-HNPs alone or after its PCD activity against Cfm. The antibacterial activity revealed high sensitivity, especially toward Gram-positive species indicating its promising ability against pathogenic issues. Interestingly, Cfm@α-HNPs showed superior anti-proliferative activity as tested by MTT assay and were able to induce apoptosis in MCF7 and HepG2 cell lines using the flow cytometry technique at 20.7% and 17% respectively. Also, The IC₅₀ of hydrogen peroxide scavenging was estimated and it was manifested that 635.8 and 665.6 μg/mL of α-HNPs before and after the PCD process of Cfm respectively.

Removal of Organic Compounds with an Amino Group during the Nanofiltration Process

The research covered the process of nanofiltration of low molecular weight organic compounds in aqueous solution. The article presents the results of experiments on membrane filtration of compounds containing amino groups in the aromatic ring and comparing them with the results for compounds without amino groups. The research was carried out for several commercial polymer membranes: HL, TS40, TS80, DL from various manufacturers. It has been shown that the presence of the amino group and its position in relation to the carboxyl group in the molecule affects the retention in the nanofiltration process. The research also included the oxidation products of selected pharmaceuticals. It has been shown that 4-Amino-3,5-dichlorophenol—a oxidation product of diclofenac and 4-ethylbenzaldehyde—a oxidation product of IBU, show poor separation efficiency on the selected commercial membranes, regardless of the pH value and the presence of natural organic matter (NOM). It has been shown that pre-ozonation of natural river water can improve the retention of pollutants removed.

A novel bio-electro-Fenton system with dual application for the catalytic degradation of tetracycline antibiotic in wastewater and bioelectricity generation

In this new insight, the potential application of the eco-friendly Bio-Electro-Fenton (BEF) system was surveyed with the aim of simultaneous degradation of tetracycline and in situ generation of renewable bioenergy without the need for an external electricity source. To shed light on this issue, catalytic degradation of tetracycline was directly accrued via in situ generated hydroxyl free radicals from Fenton's reaction in the cathode chamber. Simultaneously, the in situ electricity generation as renewable bioenergy was carried out through microbial activities. The effects of operating parameters, such as electrical circuit conditions (in the absence and presence of external resistor load), substrate concentration (1000, 2000, 5000, and 10 000 mg L⁻¹), catholyte pH (3, 5, and 7), and FeSO₄ concentration (2, 5, and 10 mg L⁻¹) were investigated in detail. The obtained results indicated that the tetracycline degradation was up to 99.04 ± 0.91% after 24 h under the optimal conditions (short-circuit, pH 3, FeSO₄ concentration of 5 mg L⁻¹, and substrate concentration of 2000 mg L⁻¹). Also, the maximum removal efficiency of anodic COD (85.71 ± 1.81%) was achieved by increasing the substrate concentration up to 2000 mg L⁻¹. However, the removal efficiencies decreased to 78.29 ± 2.68% with increasing substrate concentration up to 10 000 mg L⁻¹. Meanwhile, the obtained maximum voltage, current density, and power density were 322 mV, 1195 mA m⁻², and 141.60 mW m⁻², respectively, at the substrate concentration of 10 000 mg L⁻¹. Present results suggested that the BEF system could be employed as an energy-saving and promising technology for antibiotic-containing wastewater treatment and simultaneous sustainable bioelectricity generation.

In this new insight, the potential application of the Bio-Electro-Fenton system was surveyed with the aim of simultaneous degradation of tetracycline and in situ generation of renewable bioenergy without the need for an external electricity source.

Electrochemical Degradation of Tetracycline Using a Ti/Ta2O5-IrO2 Anode: Performance, Kinetics, and Degradation Mechanism

Tetracycline (TC) is widely used in production and in life. The high volume of its use and the difficulty of its disposal have become the most important causes of environmental pollution. A suitable method needs to be found to solve this problem. In this study, the Ti/Ta₂O₅-IrO₂ electrode was characterized for its surface morphology and crystal composition. The electrochemical catalytic ability of the Ti/Ta₂O₅-IrO₂ electrode was investigated using LSV and CV tests. The electrochemical degradation of tetracycline (TC) in water with a Ti/Ta₂O₅-IrO₂ anode was investigated. The main influence factors, such as current density (2.5–10 mA/cm²), electrode spacing (20–40 mm), initial TC concentration (20–80 mg/L) and initial solution pH (4.74–9.48) were analyzed in detail and their influences on reaction kinetics was summed up. The removal rate increased along with the increasing current density, decreasing initial TC concentration and decreasing of electrode distance under the experimental conditions. The optimum pH was 4.74. UV–vis, total organic carbon (TOC) and high-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses were used to reveal the mechanism of TC degradation. Nine main intermediates were identified, and the degradation pathways were proposed. A new insight has been postulated for the safe and efficient degradation of TC using the Ti/Ta₂O₅-IrO₂ electrode.

Removal of Tetracycline Oxidation Products in the Nanofiltration Process

The possibility of removing tetracycline (TRC) from water in an integrated advanced oxidation and membrane filtration process was investigated. Ozonation and UV/H2O2 photooxidation were applied for the destruction of TRC. Six oxidation products (OPs) retaining the structural core of TRC have been identified. One new TRC oxidation product, not reported so far in the literature, was identified—ethyl 4-ethoxybenzoate. All identified OPs were effectively retained on the membrane in the nanofiltration process. However, chemical oxygen demand (COD) measurements of the filtrates showed that in the case of UV/H2O2 oxidation, the OPs passed through the membrane into the filtrate. Various water matrices were used in the research, including the river water untreated and after ozone treatment. It has been shown that organic matter present in surface water can improve pharmaceutical retention, although it contributes to significant membrane fouling. Pre-ozonation of the river water reduced the membrane fouling. The XPS analysis was used to show ozone and H2O2 influence on the top polymer layer of the membrane. It was shown that the oxidants can damage the amide bond of the polyamide.

Photocatalytic Degradation of Tetracycline by a Novel (CMC)/MIL-101(Fe)/β-CDP Composite Hydrogel

Herein, we report a novel carboxymethyl cellulose (CMC)/MIL-101 (Fe)/poly(β-cyclodextrin) (β-CDP) hydrogel with high photocatalytic activity. β-CDP can significantly enhance the photoactivity of MIL-101(Fe) in the hydrogel prepared by a simple solvothermal method. The structure and property of this composite hydrogel were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Tetracycline was selected as a model pharmaceutical antibiotic to evaluate the photocatalytic activity of the composite hydrogel under visible light irradiation and darkness, respectively. This composite hydrogel shows excellent activity for degrading pharmaceutical antibiotics under visible light irradiation. The increased photocatalytic activity can be attributed to β-CDP, which acts as a promoter and affords an efficient separation of photogenerated electron-hole pairs of MIL-101(Fe). Moreover, the composite hydrogel is shown to have good water retainability. The hydrogel is inexpensive and shows high photocatalytic activity. Hence, it can be used as an efficient photocatalytic material.

The key factors and removal mechanisms of sulfadimethoxazole and oxytetracycline by coagulation

The effects of coagulant dosage, alkalinity, turbidity, ionic strength, and dissolved organic matter (DOM) on the removal of sulfadimethoxazole (SMZ) and oxytetracycline (OTC) by coagulation were studied and the reaction mechanisms of the coagulation process were revealed in this research. From our results, alkalinity, turbidity, ionic strength, and DOM had different effects on the removal of antibiotics. The SMZ and OTC removals were improved with increase in poly-aluminum chloride (PACl) dosage, whereas the turbidity had less influence on the removal of SMZ and OTC because the adsorption of SMZ and OTC to kaolin was low, confirmed by a control when no PACl added. The hydrolysate of PACl played a more important role than turbidity in SMZ and OTC removals. The SMZ and OTC removals were significantly increased with the increase in alkalinity, which provided a suitable condition in situ for coagulant to form more optimal species of hydrolysate. The ionic strength, which was adjusted by NaNO₃, also had a positive effect on the removal of SMZ but no obvious effect on the OTC removal. Furthermore, DOM had a higher effect on the removal of SMZ than that of OTC. In another word, if a water plant wants to improve the removal of SMZ and OTC by coagulation unit, PACl hydrolysate, alkalinity, and DOM are the three key factors to be considered primarily. Moreover, an experiment for the recovery of antibiotics from the flocs was done and the results showed that OTC and SMZ were removed by different mechanisms. The OTC was removed via complexation formed through the reaction between OTC and coagulant while the SMZ was removed through the pathway of adsorption and inter-particle bridging to the surface of coagulant hydrolysate.

Amino-functionalized mesoporous silica-magnetic graphene oxide nanocomposites as water-dispersible adsorbents for the removal of the oxytetracycline antibiotic from aqueous solutions: adsorption performance, effects of coexisting ions, and natural organic matter

The amino-functionalized mesoporous silica-magnetic graphene oxide nanocomposite (A-mGO-Si) was synthesized and used for oxytetracycline (OTC) removal from water. Various factors like the effects of initial concentration, contact time, and influence of pH were investigated. Selective adsorption experiments in connection with coexisting ions and dissolved organic matter (DOM) were also investigated. In this study, humic acid (HA) and tannic acid (TA) were representative of both hydrophobic and hydrophilic DOM, respectively. Results indicated that A-mGO-Si had an adsorption ability for OTC that was relatively greater than that of virgin magnetic graphene oxide (mGO), graphene oxide (GO), Fe₃O₄ particles, and SBA-15 mesoporous silica and also showed a better uptake removal capacity for OTC at low initial concentration in comparison with the other adsorbents. The adsorption behavior of OTC onto A-mGO-Si could be described by the pseudo-second-order kinetic model and the Freundlich isotherm model. The electrostatic interaction has no influence on the OTC absorbed when the OTC is in an aqueous medium in its zwitterion form (3.22 < pH < 7.46). At high pH, the weak π-π EDA interactions and hydrogen bonding may manifest themselves, hence causing a lower adsorption capacity. The main adsorption mechanisms were plausibly activated by H-bonding, and π-π EDA interactions, while the electrostatic interaction (cation-π interaction) might be the minor adsorption mechanism. Addition of individually exogenous ions (Na⁺, Mg²⁺, NO^-, and CO₃^2-) resulted in a decrease of OTC adsorption due to the emergence of a competitive effect. Considering the presence of HA and TA in mixed solute systems, the DOM was likely to form a stronger interaction system with mGO-Si, thereby resulting in an adsorption level which was more competitive in the process at low aqueous phase concentration of OTC. In contrast to the high aqueous phase, the coexistence of DOM could promote OTC adsorption. The phenomenon may reflect the result that a surface complexation mechanism could achieve in adsorptions.

Adsorption of chlortetracycline from aquaculture wastewater using modified zeolites

In this study, lanthanum modified zeolite (La-Z) was used to adsorb chlortetracycline (CTC) from aquaculture wastewater. La-Z was characterized by SEM, TEM, EDS, XRD, FTIR and BET. The effects various factors on the adsorption of CTC by La-Z were investigated, including the lanthanum modification concentration on zeolites, the dosage of La-Z, solution pH and reaction time. Orthogonal experiments were performed to determine the optimal adsorption conditions. Adsorption kinetics were studied by quasi-first-order model, quasi-second-order model, Weber-Morris, Boyd and Bangham models, while isotherms were analyzed by the Langmuir and Freundlich models. The removal rate reached 98.4%, when the modified concentration was 0.02 mol/L, the adsorbent dosage was 0.04 g, the initial concentration of CTC was 5 mg/L, the adsorption time was 20 min, and the pH was 7. The initial CTC concentration had the greatest influence on the adsorption process. The kinetic results showed a significant linear correlation between the experimental results and the quasi-second-order kinetic model. From the results of the internal diffusion model, it was found that the La-Z adsorption rate was controlled by both internal diffusion and external diffusion, in a multi-step process. The adsorption isotherm conforms to the Langmuir model, with the maximum adsorption quantity reaching 127.55 mg/g. Thermodynamic analysis showed that the adsorption process was an endothermic process of entropy increase, which occurs spontaneously.

Bacteria From the Multi-Contaminated Tinto River Estuary (SW, Spain) Show High Multi-Resistance to Antibiotics and Point to Paenibacillus spp. as Antibiotic-Resistance-Dissemination Players

Bacterial resistance to antibiotics is an ever-increasing phenomenon that, besides clinical settings, is generally assumed to be prevalent in environmental soils and waters. The analysis of bacteria resistant to each one of 11 antibiotics in waters and sediments of the Huelva’s estuary, a multi-contaminated environment, showed high levels of bacteria resistant mainly to Tm, among others. To further gain knowledge on the fate of multi-drug resistance (MDR) in environmental bacteria, 579 ampicillin-resistant bacteria were isolated tested for resistance to 10 antibiotics. 92.7% of the isolates were resistant to four or more antibiotic classes, indicating a high level of multi-resistance. 143 resistance profiles were found. The isolates with different MDR profiles and/or colony morphologies were phylogenetically ascribed based on 16S rDNA to phyla Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes, including 48 genera. Putative intrinsic resistance was detected in different phylogenetic groups including genera Altererythrobacter, Bacillus, Brevundimonas, Erythrobacter, Mesonia, Ochrobactrum, and Ponticaulis. Correlation of the presence of pairs of the non-intrinsic-resistances in phylogenetic groups based on the kappa index (κ) highlighted the co-habitation of some of the tested pairs at different phylogenetic levels. Maximum correlation (κ = 1.000) was found for pairs Cz^R/Tc^R in Betaproteobacteria, and Cc^R/Tc^R and Em^R/Sm^R in Sphingobacteriia at the class level, while at the genus level, was found for Cc^R/Tc^R and Nx^R/Tm^R in Mesonia, Cz^R/Tm^R and Em^R/Km^R in Paenibacillus, and Cc^R/Em^R and Rp^R/Tc^R in Pseudomonas. These results could suggest the existence of intra-class and intra-genus-transmissible genetic elements containing determinants for both members of each pair. Network analysis based on κ values higher than 0.4 indicated the sharing of paired resistances among several genera, many of them centered on the Paenibacillus node and raising the hypothesis of inter-genera transmission of resistances interconnected through members of this genus. This is the first time that a possible hotspot of resistance interchange in a particular environment may have been detected, opening up the possibility that one, or a few, bacterial members of the community could be important promoters of antibiotic resistance (AR) dissemination in this environment’s bacterial population. Further studies using the available isolates will likely give insights of the possible mechanisms and genetic elements involved.

Advanced oxidation processes on doxycycline degradation: monitoring of antimicrobial activity and toxicity

Advanced oxidation processes (AOPs) have been highly efficient in degrading contaminants of emerging concern (CEC). This study investigated the efficiency of photolysis, peroxidation, photoperoxidation, and ozonation at different pH values to degrade doxycycline (DC) in three aqueous matrices: fountain, tap, and ultrapure water. More than 99.6% of DC degradation resulted from the UV/H₂O₂ and ozonation processes. Also, to evaluate the toxicity of the original solution and throughout the degradation time, antimicrobial activity tests were conducted using Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria, and acute toxicity test using the bioluminescent marine bacterium (Vibrio fischeri). Antimicrobial activity reduced as the drug degradation increased in UV/H₂O₂ and ozonation processes, wherein the first process only 6 min was required to reduce 100% of both bacteria activity. In ozonation, 27.7 mg L^-1 of ozone was responsible for reducing 100% of the antimicrobial activity. When applied the photoperoxidation process, an increase in the toxicity occurred as the high levels of degradation were achieved; it means that toxic intermediates were formed. The ozonated solutions did not present toxicity.

Study of catalytic ozonation for tetracycline hydrochloride degradation in water by silicate ore supported Co3O4

Tetracycline hydrochloride (TCH) degradation by cobalt modified silicate ore (CoSO) catalytic ozonation in aqueous solution was investigated. CoSO catalyst was synthesized by an impregnation method using Co(NO₃)₂ as the precursor and natural silicon ore (SO) as the support. The key catalyst preparation conditions (i.e., impregnation concentration, calcination temperature and time) were optimized. The activity and stability of CoSO catalyst and its catalytic ozonation mechanism for TCH degradation were studied. The results showed that Co₃O₄ was successfully coated on the silicon ore and the CoSO catalyst was highly efficient in catalytic ozonation for TCH degradation. The TCH removal by CoSO/O₃ could reach 93.2%, while only 69.3% by SO/O₃ and only 46.0% by O₃ alone at 25 min. The reaction of TCH degradation followed pseudo-first order kinetics. TOC removal rate by CoSO/O₃ was 2.0 times higher than that by SO/O₃, and 3.5 times higher than that by O₃ alone. The reaction conditions (TCH initial concentration, catalyst concentration, pH and temperature) for catalytic ozonation were systematically investigated. The possible mechanism for the CoSO catalytic ozonation process was proposed, where hydroxyl radical oxidation mainly accounted for the substantial TCH degradation. Furthermore, CoSO showed great durability and stability after seven reaction cycles.

Antibiotic tetracycline hydrochloride was efficiently degraded by CoSO-catalytic ozonation and the catalytic oxidation mechanism was elucidated.

Optimization of sonochemical degradation of tetracycline in aqueous solution using sono-activated persulfate process

BACKGROUND

In this study, a central composite design (CCD) was used for modeling and optimizing the operation parameters such as pH, initial tetracycline and persulfate concentration and reaction time on the tetracycline degradation using sono-activated persulfate process. The effect of temperature, degradation kinetics and mineralization, were also investigated.

RESULTS

The results from CCD indicated that a quadratic model was appropriate to fit the experimental data (p < 0.0001) and maximum degradation of 95.01 % was predicted at pH = 10, persulfate concentration = 4 mM, initial tetracycline concentration = 30.05 mg/L, and reaction time = 119.99 min. Analysis of response surface plots revealed a significant positive effect of pH, persulfate concentration and reaction time, a negative effect of tetracycline concentration. The degradation process followed the pseudo-first-order kinetic. The activation energy value of 32.01 kJ/mol was obtained for US/S2O8 (2-) process. Under the optimum condition, the removal efficiency of COD and TOC reached to 72.8 % and 59.7 %, respectively. The changes of UV-Vis spectra during the process was investigated. The possible degradation pathway of tetracycline based on loses of N-methyl, hydroxyl, and amino groups was proposed.

CONCLUSIONS

This study indicated that sono-activated persulfate process was found to be a promising method for the degradation of tetracycline.

Performance of photocatalytic oxidation of tetracycline in aqueous solution by TiO2 nanofibers

The presence of pharmaceutical compounds in water and soil has become an environmental concern. The aim of this study was to evaluate the performance of TiO₂ nanofiber in the oxidation of the antibiotic tetracycline. TiO₂ nanofiber was fabricated by electro-spinning method, and then was calcined at 560°C for 2 h. Central composite design (CCD) statistic model was used to optimize tetracycline concentration, time and pH for TiO₂ catalyst. A tubular Pyrex glass reactor with diameter of 15 cm and height of 30 cm was designed and a 125W Philips HPLN lamp (UV, λ > 254 nm) was used as light source. Samples were measured by high-performance liquid chromatography (HPLC). Equation of model suggests a direct relationship between pH and time with efficiency of tetracycline removal. The observations indicated that time is the most significant (scaled estimate = + 28.04) parameter in efficiency of tetracycline removal. The application of response surface methodology yielded the equation of Y = 65.82 + 5.74 pH + 28.04 time + (−3.07)(pH)² + (−6.6)(time)², with R² = 0.986 which represents good reliability of model. Based on the response surface plots optimum conditions for degradation of tetracycline with maximum efficiency of around 95% was attained. These conditions are as follow; concentration: 50 mg/l, pH= 8.3, time= 15 min.