Tetracycline Complex Research Articles

Transforming contaminant ligands at water–solid interfaces via trivalent metal coordination

In environmental matrices, the migration and distribution of contaminants at water–solid interfaces play a crucial role in their capture or dissemination. Scientists working in environmental remediation and wastewater treatment are increasingly aware of metal–contaminant coordination; however, interfacial behaviors remain underexplored. Here, we show that trivalent metal ions (e.g. Al3+ and Fe3+) mediate the migration of pollutant ligands (e.g. tetracycline (TC) and ofloxacin) to the organic solid interface. In the absence of Al3+, humic acid (HA) colloids (50 mg/L) capture 26.1 % of the TC in water (initial concentration: 10 mg/L) via weak intermolecular interactions (binding energy: −5.71 kcal/mol). Adding Al3+ (2.5 mg/L) significantly enhances the binding of TC to an impressive 94.2 % via Al3+ mediated coordination (binding energy: −84.89 kcal/mol). The significant increase in binding energy results in superior interfacial immobilization. However, excess free Al3+ competes for TC binding via direct binary coordination, as confirmed based on the unique fluorescence of Al3+–TC complexes. Density functional theory calculations reveal the intricate process of HA–Al3+ binding via carboxyl and phenolic hydroxyl sites. The HA–Al3+ flocs then leverage the remaining coordination capacity of Al3+ to chelate with TC. As well as providing insights into the pivotal role of metal ion on the self-purification of natural water bodies, our findings on the interfacial behavior of metal–contaminant coordination will propel coagulation technology to the capture of microscale pollutants.

Illuminating tetracycline: The role of metal coordination in fluorescence emission and its optical detection potential

Rapid on-site detection of antibiotics such as tetracycline (TC) is crucial for understanding their elusive environmental fate. Fluorescence-based strategies are promising owing to their sensitivity and ease of use. This study demonstrates that Al3+–TC coordination significantly enhances the intrinsic fluorescence of TC at excitation/emission wavelengths of 395/490 and 270/490 nm. The fluorescence emission intensity is proportional to the TC concentration between 0.005 and 7.5 μmol/L TC, which increases the detection sensitivity by 40 times compared with the commonly used absorption signals. Density functional theory calculations, when combined with the independent gradient model, indicate that the six-membered chelate ring in the octahedral Al3+–TC complex restricts molecular motion, along with two intramolecular hydrogen bonds formed between TC and water ligands. These factors lead to a narrowing of the energy gap between the highest occupied and lowest unoccupied molecular orbitals upon complexation with Al3+. Consequently, the enhanced molecular rigidity and facilitated electron transfer result in a significant increase in the fluorescence quantum yield. This captivating fluorescence response significantly enhances the proficiency of optical signals in detecting TC, thereby enriching future environmental monitoring systems with greater diversity and adaptability.

Performance test and analysis of tetracycline degradation using a Micro-Nano Bubble system

Antibiotics and organic residues from Tetracycline (TC) and other pharmaceuticals administered to aquatic living organism have negative impacts on aquatic environment by killing-off non-target living organisms and developing antibiotic-resistant bacteria. In this study, Micro-Nano Bubble (MNB) system was used to remove TC residues. MNB system demonstrated good level of degradation efficiency, as resulted in experiment where in time of 100 min, the TC degraded at rate of 82.66% from its initial concentration of TC when the initial concentration was 1 mg/L. When the initial concentration was increased to 10 mg/L, MNB system degraded TC at 64.35% of their initial, this means MNB system demonstrated good level of efficiency for TC removal and indicated that it is more efficient in TC degradation under the conditions of low initial TC concentration and high availability of dissolved oxygen (DO). In the system as the temperature increased there was a significant decrease in DO saturation which was related to the TC complex structure that contain multiple function groups such as amino groups, hydroxyl and carboxyl which possess high strong affinity with oxygen that leads to their adsorption onto bubble surface. This study provides significant insights into the application of MNB system for the removal of organic residues within aquatic ecosystem and underscores the need for further exploration of MNB technology for environmental remediation.

Regional differences in lead (Pb) and tetracycline (TC) binding behavior of sediment dissolved organic matter (SDOM): Effects of DOM heterogeneity and microbial degradation

Lake Nansi, primarily dominated by macrophytes, faces threats from heavy metals and antibiotics due to human activity. This study investigated sediment dissolved organic matter (SDOM) characteristics and complexation of lead (Pb) and tetracycline (TC) in barren zone (BZ) and submerged macrophytes zone (PZ). Additionally, a microbial degradation experiment was conducted to examine its impact on the regional variations in complexation. SDOM abundance and protein-like materials in PZ was significantly greater than in BZ, indicating a probable contribution from the metabolism and decomposition of submerged macrophytes. Both zones exhibited a higher affinity of SDOM for Pb compared to TC, with all four components participating in Pb complexation. Protein-like materials in PZ had a higher binding ability (LogKPb=4.19 ± 1.07, LogKTC=3.89 ± 0.67) than in BZ (LogKPb=3.98 ± 0.61, LogKTC=3.69 ± 0.13), suggesting a potential presence of organically bound Pb and TC due to the higher abundance of protein-like materials in PZ. Although microbial communities differed noticeably, the degradation patterns of SDOM were similar in both zones, affecting the binding ability of SDOM in each. Notably, the fulvic-like component C4 emerged as the dominant binding material for both Pb and TC in both zones. Degradation might increase the amount of organically bound TC due to the increase in the LogKTC.

Influence of surfactant molecular features on tetracycline transport in saturated porous media of varied surface heterogeneities

This study aims to understand how surfactants affect the mobility of tetracycline (TC), an antibiotic, through different aquifer media. Two anionic and cationic surfactants, sodium dodecylbenzene sulfonate (SDBS) and cetyltrimethyl ammonium bromide (CTAB), were used to study their influence on TC mobility through clean sand and humic acid (HA)-coated sand. HA coating inhibits TC mobility due to its strong interaction with TC. Both surfactants promoted TC mobility at pH 7.0 due to competitive deposition, steric effect, and increased hydrophilicity of TC. CTAB had a more substantial effect than SDBS, related to the surfactants' molecular properties. Each surfactant's promotion effects were greater in HA-coated sand than in quartz sand due to differences in surfactant retention. CTAB inhibited TC transport at pH 9.0 due to its significant hydrophobicity effect. Furthermore, in the presence of Ca2+, SDBS enhanced TC transport by forming deposited SDBS-Ca2+-TC complexes. On the other hand, CTAB increased TC mobility due to its inhibition of cation bridging between TC and porous media. The findings highlight surfactants' crucial role in influencing the environmental behaviors of tetracycline antibiotics in varied aquifers.

Aggregation-induced emission carbon dots as Al3+-mediated nanoaggregate probe for rapid and selective detection of tetracycline

Worldwide abuse of tetracycline (TC) seriously threatens environmental safety and human health. Metal-TC complexes formed by residual TC in the environment can also contribute to the spread of antibiotic resistance. Therefore, monitoring of TC residues is still required. Here, we report novel aggregation-induced emission carbon dots (AIE-Cdots) as nanoaggregate probes for the rapid and selective detection of TC residue. Riboflavin precursors with rotational functional groups led to the development of AIE-Cdots. The aggregation of AIE-Cdots was induced selectively for Al3+, amplifying the fluorescence signals owing to the restricted rotation of the side chains on the AIE-Cdot surface. The fluorescence signal of such Al3+-mediated nanoaggregates (Al3+-NAs) was further triggered by the structural fixation of TC at the Al3+ active sites, suggesting the formation of TC-coordinated Al3+-NAs. A linear correlation was observed in the TC concentration range of 0–10 μM with a detection limit of 42 nM. In addition, the strong Al3+ binding affinity of AIE-Cdots produced similar NAs and enhanced fluorescence signals in Al3+–TC mixtures. These AIE-Cdots-based nanoplatforms have a rapid response, good selectivity, and reliable accuracy for detecting TC or aluminum complexes, meeting the requirements for hazardous substance monitoring and removal in environmental applications.

Cu(II) inhibited the transport of tetracycline in porous media: role of complexation.

Tetracycline (TC) and Cu(II) coexist commonly in various waters, which may infiltrate into the subterranean environment through runoff and leaching, resulting in substantial ecological risks. However, the underlying mechanisms why Cu(II) affects the transport of TC in porous media remain to be further explored and supported by more evidence, especially the role of complexation. In this study, the transport of TC with coexisting Cu(II) was comprehensively explored with column experiments and density functional theory (DFT) calculation. At natural environmental concentrations, Cu(II) significantly inhibited the transport of TC in the quartz sand column. Cu(II) augmented the retention of TC in the column mainly via electrostatic force and complexation. The interaction between TC and TC-Cu complexes on the surface of SiO2 was investigated with first-principles calculations for the first time. There were strong van der Waals forces and coordination bonds on the surface of complexes and SiO2, leading to higher adsorption energy than that of TC and inhibiting its penetration. This study offers novel insights and theoretical framework for the transport of antibiotics in the presence of metal ions to better understand the fate of antibiotics in nature.

Fabrication and optimization of paper chips from calcinated Fe-MOFs for rapid and in situ visual detection of tetracyclines in water environments

Antibiotics such as tetracyclines (TCs) have become a major threat to ecosystem safety and human health, as their abuse has caused the occurrence and proliferation of antibiotic-resistant bacteria and genes. Currently, there is still a lack of convenient in situ methods for the detection and monitoring of TC pollution in actual water systems. This research reports a paper chip based on the complexation of iron-based metal organic frameworks (Fe-MOFs) and TCs for rapid and in situ visual detection of representative oxytetracycline (OTC) pollution in water environments. The optimized complexation sample NH2-MIL-101(Fe)− 350 obtained by calcination at 350 °C exhibited the highest catalytic activity and was then used for paper chip fabrication by printing and surface modification. Notably, the paper chip demonstrated a detection limit as low as 17.11 nmol L−1 and good practicability in reclaimed water, aquaculture wastewater, and surface water systems, with OTC recovery rates of 90.6–111.4%. More importantly, the presence of dissolved oxygen (9.13–12.7 mg L−1), chemical oxygen demand (0.52–12.1 mg L−1), humic acid (< 10 mg L−1), Ca2+, Cl–, and HPO42– (< 0.5 mol L−1) had negligible interference on the detection of TCs by the paper chip. Therefore, this work has developed a promising method for rapid and in situ visual monitoring of TC pollution in actual water environments.

Reevaluation for UV photolysis of Fe(III) inducing tetracycline abatement: Overlooked significance of complexation-assistance in environmental fates of antibiotics

Interaction of antibiotics with metal ions in aquatic environments, commonly occurring to form complexes, may affect the migration, transformation and reactivity of residual antibiotics. This study demonstrates the photolysis of Fe(III) by UV irradiation at pH 3.5, as an advanced oxidation process, to produce •OH for the abatement of a common broad-spectrum antibiotic compound, tetracycline (TET). The dimethylamino (-N(CH3)2) and hydroxyl (-OH) groups of TET were determined as the binding sites for the complexation with Fe(III) via a series of novel characterization approaches. The complexation stoichiometry of Fe(III)-TET complexation, including the complexation ratio, constants and percentages, was determined via a complexometric titration based on the UV differential spectroscopy. The complexation constant was determined to be 21,240 ± 1745 L·mol−1 under the designed conditions. Complexation of TET with Fe(III) enhanced its degradation in the UV/Fe(III) process, through the promotion of the •OH generation by inhibiting hydrolysis-precipitation process of Fe(III) and enhancing Fe(III)/Fe(II) cycle and the acceleration of mass transfer between •OH and TET. This finding provides new insights into the role of complexation in the fate of residual antibiotics in the UV/Fe(III) process. The reduced overall ecotoxicity during the TET abatement, evaluated by the toxicity variation through ECOSAR program, provides the UV/Fe(III) process with a theoretical feasibility for water decontamination in actual applications.

Construction of core-shell Fe3O4@MoS2 activates peroxymonosulfate for the degradation of tetracycline: Structure-activity relationship, performance and mechanisms

Peroxymonosulfate (PMS) is an excellent oxidant that can produce multiple radicals. A novel core-shell composite Fe3O4 @MoS2-x (F@M-x) heterostructure was synthesized to degrade tetracycline (TC) by PMS activation. In F@M/PMS catalytic system, more Fe(III) is reduced into Fe(II) by doping MoS2 nanoflowers formed core-shell structure, resulting in the catalytic process being significantly enhanced. Due to the strong complexation tendency of TC towards Fe(II), the Fe(II)-TC complexes* accumulated between the core and shell, which significantly accelerates the PMS activation and TC abatement compared to free Fe(II). The EPR and quenching experimental results revealed that O2•− and 1O2 were detected as the main active species for TC degradation in the F@M/PMS system. Furthermore, the possible TC degradation pathways were proposed and the toxicity estimation of intermediates was evaluated by Toxicity QSAR prediction. These results will be useful for the improvement of PMS-based AOPs activation and expand the application of Fe(II)/PMS systems in the treatment of water containing new organic micro-pollutants.

Elucidation of the binding behavior between tetracycline and bovine casein by multi-spectroscopic and molecular simulation methods

Bovine casein was used as a model protein to explore the binding behavior of food matrix with residual antibiotics. The interaction mechanism between casein and tetracycline (TC) was characterized by fluorescence quenching and isothermal titration calorimetry. Through forming the non-fluorescent ground-state complex, TC effectively quenched the endogenous fluorescence of casein. The formed casein-TC complex was maintained by hydrogen bonding, electrostatic and hydrophobic interactions (ΔH < 0, ΔS > 0). Circular dichroism and infrared spectroscopic studies indicated that the complexation of TC did not affect the secondary structure of casein. Molecular docking further theoretically validated the main interaction forces and deciphered the amino acid residues surrounding the antibiotic in the casein binding pocket. Interestingly, 1H NMR results demonstrated the π-π stacking interaction formed between PHE-189 and the benzene ring of TC, which was consistent with the docking findings. Besides, saturation transfer difference (STD) NMR revealed that the binding of TC engages its –N(CH3)2 group. This study sheds new light on the transition of residual antibiotics from the free to the bound state in foodstuffs.

Complexation determines the removal of multiple tetracyclines by ferrate

Complexation of tetracyclines with Fe species can be expected during oxidation by ferrate and be part of the complicated reactions that lead to the transformation of tetracyclines. Herein, we focused on the role of complexation in four tetracyclines removals by ferrate. The quenching experiment, desorption experiment, total organic carbon detection, and UV absorbance characterization demonstrated that, for the removal of tetracyclines, the complexation of tetracyclines with Fe3+ (derived from the reduction and decomposition of ferrate) contributed ∼79 %, followed by ∼11 % oxidation and ∼10 % adsorption/flocculation. Density functional theory calculations rationalized the formation of Fe-tetracyclines complexes and reactions of ferrate and hydroxyl radicals with each tetracycline. Thermodynamic and kinetic calculations indicated that complexation reactions between Fe3+ and tetracyclines were more likely to occur than oxidation reactions between ferrate and hydroxyl radicals. The complexation rate was highest for tetracycline and lowest for chlortetracycline, and the order of complexation rates was consistent with the experimental removal ratios of four tetracyclines. Complexation rates of tetracyclines with Fe3+ determine the removal of multiple tetracyclines by ferrate rather than oxidation rates. Insights based on forming Fe-tetracyclines complexes differed from the reported oxidation mechanisms, and complexation cannot be negligible in removing pollutants due to the potential secondary release.

Complexation and degradation of tetracycline by activation of molecular oxygen with biochar-supported nano-zero-valent copper composite.

Nano-zero-valent copper (nZVC) is a superior molecular oxygen (O2) activator for the abatement of organic pollutants due to its high electron utilization rate. However, the activation efficiency of O2 is compromised by the agglomeration tendency of nZVC particles and the concomitant reduction of the available active sites. To address this problem, the biochar (BC) with porous structure and abundant surface functional groups is utilized to disperse and stabilize nZVC for O2 activation (simplified as the nZVC/BC/O2 system) for efficient removal of tetracycline (TC). The nZVC/BC composite possesses a high specific area with well-distributed nZVC particles on the BC surface, which guarantees the superior dispersion and high reactivity in the activation of O2. The efficacy of the nZVC/BC/O2 system for TC abatement is evaluated and the underlying mechanism is elucidated. The results show that nZVC/BC/O2 system can achieve excellent removal of TC with the efficiencies of more than 85% in the pH range of 4.0-9.0, which originated from the combined action of complexation and degradation. The degradation is dominated by reactive oxygen species (ROS) including •OH, •O2- and 1O2 generated by Cu0/Cu+ activated O2 while the generation of Cu2+ via oxygen oxidation on the surface of nZVC/BC can remove TC by complexation adsorption. This study highlights the complexation and degradation in the removal of TC and can be expected to exhibit application prospects in the water and wastewater treatment.

Zinc Ion-Based Switch-on Fluorescence-Sensing Probes for the Detection of Tetracycline

Tetracycline (TC) is an antibiotic that has been widely used in the animal husbandry. Thus, TC residues may be found in animal products. Developing simple and sensitive methods for rapid screening of TC in complex samples is of great importance. Herein, we demonstrate a fluorescence-sensing method using Zn2+ as sensing probes for the detection of TC. Although TC can emit fluorescence under the excitation of ultraviolet light, its fluorescence is weak because of dynamic intramolecular rotations, leading to the dissipation of excitation energy. With the addition of Zn2+ prepared in tris(hydroxymethyl)amino-methane (Tris), TC can coordinate with Zn2+ in the Zn2+-Tris conjugates to form Tris-Zn2+-TC complexes. Therefore, the intramolecular motions of TC are restricted to reduce nonradiative decay, resulting in the enhancement of TC fluorescence. Aggregation-induced emission effects also play a role in the enhancement of TC fluorescence. Our results show that the linear dynamic range for the detection of TC is 15-300 nM. Moreover, the limit of detection was ~7 nM. The feasibility of using the developed method for determination of the concentration of TC in a complex chicken broth sample is also demonstrated in this work.

Tetracycline adsorption trajectories on aged polystyrene in a simulated aquatic environment: A mechanistic investigation

Microplastics (MPs) have attracted widespread attention as an organic class of pollutants as well as pollutant carriers in recipient aquatic ecosystems. In this study, tetracycline (TC) adsorption by polystyrene (PS), with multiple aging-based temporal changes in the adsorption mechanism, was observed. The results revealed that the pseudo-second-order model accurately predicted the TC adsorption kinetics for different types of PS. In addition, the isothermal adsorption processes fit the Freundlich model; however, their interactions were drastically weakened at lower temperatures or increasing salinities. Corresponding to the electrostatic interactions, adsorption TC was largely pH-dependent, with the maximum adsorbed TC content on the PS surface at a pH of 5 in an aqueous environment. More importantly, mechanistic studies have revealed that, compared to virgin PS, TC complexes with aged PS are principally controlled by hydrogen bonding and ionic interactions, followed by π–π, polar-polar, and van der Waals interactions. These findings will aid in understanding the insights of TC and aged PS interactions and the underlying interactive molecular forces, which will be advantageous for comprehending the real case scenario of inter-pollutant interactions and related environmental pollution.

Adsorption behavior of aged polybutylece terephthalate microplastics coexisting with Cd(II)-tetracycline.

Microplastics (MPs) are one of the emerging classes of pollutants that can be infiltrated into any aqueous solutions from disposed toxic metals and antibiotics, further exacerbating the potential biotoxicity of MPs. However, the research on the interaction between MPs and various pollutants is limited. Therefore, in this study, the changes in toxicity of polybutylece terephthalate (PBT) MPs were assessed following adsorption of heavy metals and antibiotics. The adsorption behavior of Cd(II) and tetracycline (TC) on ultraviolet (UV) light-aged PBT was investigated. The results demonstrated that the Cd(II) adsorption behavior could be described by the pseudo-second-order kinetic and Langmuir isothermal models, while the TC adsorption behavior has well fitted using Elovich and Sips models. The whole adsorption process occurred via either external diffusion or internal diffusion. The interactions between aged PBT and pollutants were evaluated under different environmental conditions, such as solution pH and the concentrations of dissolved organic matter and cations. The amounts of Cd(II) and TC adsorbed were higher in the competitive systems than the single solution, which might attribute to the formation of Cd(II)-TC complexes and aged PBT functional group changes. The results of two-dimensional correlation spectroscopy (2D-COS) describes the sequence of functional group transformation during the uptake of Cd(II)-TC by aged PBT in binary systems. These findings identify a strong interaction between aged PBT and contaminants, establishing the potential fate of aged MPs under natural aquatic environment conditions.

Microsecond-resolved smartphone time-gated luminescence spectroscopy.

Time-gated luminescence spectra are usually measured by laboratory instruments equipped with high-speed excitation sources and spectrometers, which are always bulky and expensive. To reduce the reliance on expensive laboratory instruments, we demonstrate the first, to the best of our knowledge, use of a smartphone for the detection of time-gated luminescence spectra. A mechanical chopper is used as the detection shutter and an optical switch is placed at the edge of the wheel to convert the chopping signal into a transistor-transistor logic (TTL) signal which is used to control the excitation source and achieve synchronization. The time-gated luminescence spectra at different delay times of Eu(TTA)3 powder and the solutions of Eu-tetracycline complex are successfully detected with a temporal resolution of tens of microseconds by the proposed approach. We believe our approach offers a route toward portable instruments for the measurement of luminescence spectra and lifetimes.

Antibacterial nanofibers of pullulan/tetracycline-cyclodextrin inclusion complexes for Fast-Disintegrating oral drug delivery

Tetracycline is a widely used antibiotic suffering from poor water solubility and low bioavailability. Here, hydroxypropyl-beta-cyclodextrin (HPβCD) was used to form inclusion complexes (IC) of tetracycline with 2:1 M ratio (CD:drug). Then, tetracycline-HPβCD-IC was mixed with pullulan- a non-toxic, water-soluble biopolymer - to form nanofibrous webs via electrospinning. The electrospinning of pullulan/tetracycline-HPβCD-IC was yielded into defect-free nanofibers collected in the form of a self-standing and flexible material with the loading capacity of ∼ 7.7 % (w/w). Pullulan/tetracycline nanofibers was also generated as control sample having the same drug loading. Tetracycline was found in the amorphous state in case of pullulan/tetracycline-HPβCD nanofibers due to inclusion complexation. Through inclusion complexation with HPβCD, enhanced aqueous solubility and faster release profile were provided for pullulan/tetracycline-HPβCD-IC nanofibers compared to pullulan/tetracycline one. Additionally, pullulan/tetracycline-HPβCD-IC nanofibers readily disintegrated when wetted with artificial saliva while pullulan/tetracycline nanofibers were not completely absorbed by the same simulate environment. Electrospun nanofibers showed promising antibacterial activity against both gram-positive and gram-negative bacteria. Briefly, our findings indicated that pullulan/tetracycline-HPβCD-IC nanofibers could be an attractive material as orally fast disintegrating drug delivery system for the desired antibiotic treatment thanks to its promising physicochemical and antibacterial properties.

The effect of complexation with metal ions on tetracycline degradation by Fe2+/3+ and Ru3+ activated peroxymonosulfate

The possible effect of complexation of tetracycline (TC) with metal ions on the degradation of TC by homogeneous activated peroxymonosulfate (PMS) was investigated. The oxidation kinetics of TC indicated the differences in PMS activation ability by Fe2+/3+ and Ru3+. Fe2+/3+ could activate PMS to generate HO• and SO4-• as is known, while Ru3+promoted the generation of 1O2 from PMS, though 1O2 may be not the only and dominant oxidant. The stronger complex ability of Ru3+ and Fe3+ with TC than Fe2+ contributed to the enhanced oxidation of TC in Fe3+/PMS and Ru3+/PMS systems. The complexation facilitated TC degradation possibly due to the electron reconfiguration of metal ions and TC, such as reduce the stability of -C–C- double bands in TC structures and made it more vulnerable. The complexation reactions were commonly occurred but ignored in metal species activated PMS systems, the findings in this study suggested that the interaction between metal ions and organic contaminants should be reconsidered and utilized in the development of AOPs.

Removal characteristics and mechanism of microplastics and tetracycline composite pollutants by coagulation process

Water composite pollution is an increasingly severe challenge in the field of water treatment. Especially, microplastic is an emerging concerned pollutant in recent years for its persistent eco-environmental influence. Therefore, investigating the composite pollution effect and developing effective removal technology surrounding microplastic is an urgent task for future need. In this aspect, the removal of composite pollutants, microplastics (PET/weathered PET) and tetracycline (TC), was procedurally studied by coagulation with AlCl3. Based on the analysis of variance (ANOVA) and correlation of experimental data, the characterization of fourier transform infrared spectroscopy (FTIR), solid-state 27Al nuclear magnetic resonance (27Al NMR), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) computation, the removal mechanism for coagulation was well discussed and proposed. It shows that the removal performance of individual PET and TC were mainly influenced by coordination reaction in forming Al-PET and Al-TC, corresponding to the removal rate of 100% and 28%, respectively. Charge neutralization and sweeping flocculation played an auxiliary role for PET removal. However, the weathered PET (WPET) exhibited worse removability (92%) than PET due to a sharp decrease in the hydrodynamic diameter of WPET. The poor removal of TC was induced by the formation of Al-TC which was difficult to transform into solid flocs. In regard to composite pollutants, the removal rate of PET was significantly decreased (91%) due to the low activity of TC in forming flocs and the complexation competition, while the removal of TC was greatly enhanced (41%). In this process of multilayered reaction among PET, TC and Al3+, Al3+ preferentially interacted with TC to form Al-TC, which was subsequently combined to PET to form the ternary complexes PET-Al-TC, thus realizing the transformation from dissolved TC complexes to solid TC composites. This work is of great significance in understanding the interaction mechanism of composite pollutants in coagulation process.