**3. The antibiotics photodecomposition products**

The electrospray ionization mass spectrometry (ESI-MS) analytical technique measures the EPs methylene blue (MB) photodecomposition. Before the photodecomposition reaction, the methylene blue compound was m/z 284 (**Figure 1(a)**), and after 1 day of photodecomposition, there are several peaks (**Figure 1(b)**). Those peaks were MB fragment degradation compounds with m/z values of 109, 129, and 165. Those peaks have the relative intensity of 37.3, 44.2, and 40.5% considering the original MB peak of 100% with m/z 284 (**Figure 1(a)**).

The EPs dye photosensitization process involves the dye initial electronic excitation D to D\* induced by hν incident radiation energy which ejects one electron in the semiconductor (SC) conduction band [8, 16, 17]. The emitted electron reacts with the environment oxygen oxidizing the radial D\*o, and the total process results in colorless products, Eq. (6).

the MB adsorbs little in the UVA region. The elimination of the photogenerated holes by the

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The colorless species identified as Leuco methylene blue (LMB) is readily re-oxidized to MB

ble, **Figure 2**. This environmental condition also ensures that the traditional dye-sensitized

The MB is excited under the red region of the light source and received electrons to the excited MB which produces an anion which abstracts a proton from water to provide LMB; the LMB is very readily re-oxidized back to MB if there is any oxygen in the solution [9, 10, 21]. The CG results showed no change in the MB concentration for the first few minutes of reaction, but if the reaction progresses, efficiently all molecules of MB will be converted to LMB. Subsequently, the visual observation indicates that the intense blue color of the solution starts to disappear as the reaction progresses as an effect of the photoreduction of the MB to LMB at the adsorption band of MB. Experimental results indicated the irradiation of the MB at 365 nm in the absence, and the presence of glycerol electron donor occurs, and the MB rapidly photobleached via an oxidative route with LMB primary production in 15 min. The air pres-

ence also quickly reduced the LMB to MB, gaining 92% of the original color.

**Figure 2.** Scheme for photodecomposition mechanism of MB and the Leuco MB (LMB) production [9, 10].

and has to be produced and maintained in anaerobic conditions to be sta-

(5)

85

(6)

glycerol, which acts as an SED, followed the reduction reaction.

Photocatalyzed MB redox reaction:

bleaching reaction cannot occur [19, 20].

by ambient O2

**Figure 1.** ESI-MS spectra of methylene blue photodecomposition (a) before and (b) after degradation of 1 day (adapted from Kobzi et al. [27]) [8].

The study provides some example of dye sensitization, and the photosensitized bleaching occurring under visible light and an aerated aqueous dispersion of TiO2 . The light absorbed by the dye alone was able to promote its rapid and complete photobleaching. The photonic efficiency η for the visible photobleaching of the MB is already known, and it is a function of the incident radiation wavelength. The spectrum η versus λ plot was similar in shape to the diffuse reflectance spectrum (DRS) of the MB adsorbed on TiO<sup>2</sup> with a peak at 665 nm which is the wavelength of the maximum adsorption for MB.

By contrast, the dye photolysis involves the electronically excited state of the dye which is either unstable and quenched by ambient O2 to produce singlet oxygen which oxidizes the dye. Considering only the equation, it is not surprising if the rate of dye bleaching due to photolysis is often unchanged in the absence of the semiconductor. When the photolysis and photosensitization are examined, the presence of SC enhances the production of the bleached product.

$$\mathbf{D} + \mathbf{h}\mathbf{v}^{\cdot} \xrightarrow{\cdot} \mathbf{D}^{\ast} \left( \mathbf{\dot{\bullet}} \mathbf{O}\_{2} \right) \xrightarrow{\cdot} \mathbf{\dot{\bullet}} \mathbf{B} \text{leached products} \tag{4}$$

The rapid and irreversible reduction of the photogenerated holes by glycerol followed the reduction reaction and the molar absorptivity of 4.7000 M−1 cm−1 at 620 nm. The glycerol behaves as an SED which is also present in the ink film. The MB photocatalytic process runs as follows:

The use of photocatalyst indicator (paiis) helps to measure the electron generation efficiency of the TiO2, changing from blue redox dye Resazurin (Rz) to pink Resorufin (Rf). The Rz as the MB adsorbs little in the UVA region. The elimination of the photogenerated holes by the glycerol, which acts as an SED, followed the reduction reaction.

Photocatalyzed MB redox reaction:

The study provides some example of dye sensitization, and the photosensitized bleaching

**Figure 1.** ESI-MS spectra of methylene blue photodecomposition (a) before and (b) after degradation of 1 day (adapted

by the dye alone was able to promote its rapid and complete photobleaching. The photonic efficiency η for the visible photobleaching of the MB is already known, and it is a function of the incident radiation wavelength. The spectrum η versus λ plot was similar in shape to the

By contrast, the dye photolysis involves the electronically excited state of the dye which is

dye. Considering only the equation, it is not surprising if the rate of dye bleaching due to photolysis is often unchanged in the absence of the semiconductor. When the photolysis and photosensitization are examined, the presence of SC enhances the production of the

D + hv" D<sup>∗</sup> (+O2)Bleached products (4)

The rapid and irreversible reduction of the photogenerated holes by glycerol followed the reduction reaction and the molar absorptivity of 4.7000 M−1 cm−1 at 620 nm. The glycerol behaves as an SED which is also present in the ink film. The MB photocatalytic process runs

The use of photocatalyst indicator (paiis) helps to measure the electron generation efficiency of the TiO2, changing from blue redox dye Resazurin (Rz) to pink Resorufin (Rf). The Rz as

. The light absorbed

with a peak at 665 nm which

to produce singlet oxygen which oxidizes the

occurring under visible light and an aerated aqueous dispersion of TiO2

diffuse reflectance spectrum (DRS) of the MB adsorbed on TiO<sup>2</sup>

84 Emerging Pollutants - Some Strategies for the Quality Preservation of Our Environment

is the wavelength of the maximum adsorption for MB.

either unstable and quenched by ambient O2

bleached product.

from Kobzi et al. [27]) [8].

as follows:

$$\begin{aligned} \text{(\text{Gylcercol} + \text{Rx} &= \underbrace{\text{LSC}}\_{\text{Hy} < \text{= END}} \times \text{Gly} \\\\ \text{(\text{Gylcercol} + \text{MBS} &= \text{LSC})} \\\\ \text{(\text{Gylcercol} + \text{MBS} &= \underbrace{\text{LSC}}\_{\text{Hy} < \text{= Edg}} \times \text{Gby} \\\\ \text{(\text{Gylcercol} + \text{MBS} &= \text{LSC})} \end{aligned} \tag{\text{(\text{Gylcercol} + \text{MBS} = \text{LSC})} $$

The colorless species identified as Leuco methylene blue (LMB) is readily re-oxidized to MB by ambient O2 and has to be produced and maintained in anaerobic conditions to be stable, **Figure 2**. This environmental condition also ensures that the traditional dye-sensitized bleaching reaction cannot occur [19, 20].

The MB is excited under the red region of the light source and received electrons to the excited MB which produces an anion which abstracts a proton from water to provide LMB; the LMB is very readily re-oxidized back to MB if there is any oxygen in the solution [9, 10, 21]. The CG results showed no change in the MB concentration for the first few minutes of reaction, but if the reaction progresses, efficiently all molecules of MB will be converted to LMB. Subsequently, the visual observation indicates that the intense blue color of the solution starts to disappear as the reaction progresses as an effect of the photoreduction of the MB to LMB at the adsorption band of MB. Experimental results indicated the irradiation of the MB at 365 nm in the absence, and the presence of glycerol electron donor occurs, and the MB rapidly photobleached via an oxidative route with LMB primary production in 15 min. The air presence also quickly reduced the LMB to MB, gaining 92% of the original color.

**Figure 2.** Scheme for photodecomposition mechanism of MB and the Leuco MB (LMB) production [9, 10].

The photocatalytic dye bleaching process using the λ = 617 nm is much slower than the reaction mediated by TiO2 and λ = 365 nm light. The MB/glycerol has the potential as the dye-based test for UV presence, and visible absorbing photocatalytic materials provided by photocatalyst test.

The redox potential for the reduction of MB at pH 7 to LMB is 0.011 v, whereas for oxygen it depends on electron transference and how many are present. For 4e-, O2 /H2 O (0.815 v) and for 1 electron O2 /O2 - (−0.33 v). It is not obvious that an SC is capable of reducing MB to LMB and also will be able to reduce O2 . The oxi-reduction indicator dyes are important to visualize the redox chemistry and measure the dye environmental oxidation/reduction.

The environmental antibiotics resistance to widely used medical and veterinary medicine is a serious problem and poses a significant threat to the health of humans and livestock infected with resistant bacterial strains. The alarming fact is that resistant genes can be mobilized between various environmental compartments and transferred into the food chain. The conventional processes associated with sewage treatment, hydrolysis, biodegradation, and sorption are ineffective for the removal of many antibiotics, and thus the photodegradation may be the predominant transformation pathway for antibiotics deactivation in the environment.

The UV spectra of amoxicillin (AMX) and the amoxicillin decomposition products (ADPs) as ADP1,2, ADP4,5, and ADP8,9 consisted of two peaks at λ = 230 and 275 nm, similar with AMX. This effect is due to the para-substituted phenolic group, which do not change in the AMX and ADPs skeleton (**Figures 3** and **4**) and is the primary contributor to the observed UV spectra. Those peaks enable a quantitative calculation of these ADPs in the environment based on the assumption that the UV RF is relatively similar for AMX and its ADPs at λ = 230 nm.

> On the other hand, the compound ADP¨6 has conjugated double bonds (**Figure 3**), and thus, its UV spectrum consists of two different peaks at λ = 240 and 250 nm. The calculation and quantification of ADP could not be in the environment due to the incompatibility of the AMX

> **Figure 4.** UV spectra of (a) amoxicillin and degradation products ADP1,2, ADP4,5, and ADP8,9 and (b) the degradation

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The confirmation of the proposed AMX DP structures was by comparison of the H NMR spectra of the AMX and those of purified ADP. **Figure 4** presents the degradation schematics of the AMX to its ADPs, the products ADP1,2, ADP4,5, and ADP8,9 are epimers, and preparative

The penicilloic acid epimers (ADP4,5) are rapidly isomerized and become stable at an isomer ratio of 3:2, so the NMR spectra could not be obtained separately, **Table 1**. The isomers spectrum showed that H in the AMX spectrum is δ = 5.44 ppm, consisting of two hydrogen atoms, which shift to a higher field and become H-6a and H6b δ = 5.18 and 4.46 ppm, the ADP3 and

In recent years, the water-quality monitoring results indicated the presence of antibiotics and antibiotics residues in aquatic environments in many countries, including Europe, North America, and Asia. In addition, the antibiotic-resistant bacteria have become a serious problem worldwide, caused by the excessive use and incorrect discharge of antibiotics into the environment. The use of ampicillin (AMP) is worldwide, as an essential antibiotic but this organic molecule rapidly decomposes in water containing bivalent cations as Ca2+ and Mg2+ and their

and ADP6 UV spectrum at λ = 230 nm.

ADP 8,9.

product ADP6 [11].

purification was carried out separately for each.

**Figure 3.** Suggested photodegradation pathway of amoxicillin in an aqueous medium (adapted from Gozlan et al., 2010) [7].

The photocatalytic dye bleaching process using the λ = 617 nm is much slower than the reaction

for UV presence, and visible absorbing photocatalytic materials provided by photocatalyst test. The redox potential for the reduction of MB at pH 7 to LMB is 0.011 v, whereas for oxygen it

The environmental antibiotics resistance to widely used medical and veterinary medicine is a serious problem and poses a significant threat to the health of humans and livestock infected with resistant bacterial strains. The alarming fact is that resistant genes can be mobilized between various environmental compartments and transferred into the food chain. The conventional processes associated with sewage treatment, hydrolysis, biodegradation, and sorption are ineffective for the removal of many antibiotics, and thus the photodegradation may be the predominant transformation pathway for antibiotics deactivation in the environment. The UV spectra of amoxicillin (AMX) and the amoxicillin decomposition products (ADPs) as ADP1,2, ADP4,5, and ADP8,9 consisted of two peaks at λ = 230 and 275 nm, similar with AMX. This effect is due to the para-substituted phenolic group, which do not change in the AMX and ADPs skeleton (**Figures 3** and **4**) and is the primary contributor to the observed UV spectra. Those peaks enable a quantitative calculation of these ADPs in the environment based on the assumption that the UV RF is relatively similar for AMX and its ADPs at λ = 230 nm.

**Figure 3.** Suggested photodegradation pathway of amoxicillin in an aqueous medium (adapted from Gozlan et al.,

depends on electron transference and how many are present. For 4e-, O2

86 Emerging Pollutants - Some Strategies for the Quality Preservation of Our Environment

redox chemistry and measure the dye environmental oxidation/reduction.

and λ = 365 nm light. The MB/glycerol has the potential as the dye-based test


. The oxi-reduction indicator dyes are important to visualize the

/H2

O (0.815 v) and for

mediated by TiO2

1 electron O2

2010) [7].

/O2

also will be able to reduce O2

**Figure 4.** UV spectra of (a) amoxicillin and degradation products ADP1,2, ADP4,5, and ADP8,9 and (b) the degradation product ADP6 [11].

On the other hand, the compound ADP¨6 has conjugated double bonds (**Figure 3**), and thus, its UV spectrum consists of two different peaks at λ = 240 and 250 nm. The calculation and quantification of ADP could not be in the environment due to the incompatibility of the AMX and ADP6 UV spectrum at λ = 230 nm.

The confirmation of the proposed AMX DP structures was by comparison of the H NMR spectra of the AMX and those of purified ADP. **Figure 4** presents the degradation schematics of the AMX to its ADPs, the products ADP1,2, ADP4,5, and ADP8,9 are epimers, and preparative purification was carried out separately for each.

The penicilloic acid epimers (ADP4,5) are rapidly isomerized and become stable at an isomer ratio of 3:2, so the NMR spectra could not be obtained separately, **Table 1**. The isomers spectrum showed that H in the AMX spectrum is δ = 5.44 ppm, consisting of two hydrogen atoms, which shift to a higher field and become H-6a and H6b δ = 5.18 and 4.46 ppm, the ADP3 and ADP 8,9.

In recent years, the water-quality monitoring results indicated the presence of antibiotics and antibiotics residues in aquatic environments in many countries, including Europe, North America, and Asia. In addition, the antibiotic-resistant bacteria have become a serious problem worldwide, caused by the excessive use and incorrect discharge of antibiotics into the environment.

The use of ampicillin (AMP) is worldwide, as an essential antibiotic but this organic molecule rapidly decomposes in water containing bivalent cations as Ca2+ and Mg2+ and their


The β-lactams antibiotics such as ampicillin, penicillins, cephalosporins, and oxicephalosporins inhibit biosynthesis of the bacterial cell wall by acylating and thereby inactivating transpeptidases. The antibacterial activity depends on the β-lactams rings, and some complex

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**Figure 6.** The photodecomposition scheme for ampicillin and its by-products.

**Figure 7.** The complex formation with Cu-ampicillin chemical structure as a complex ligand.

**Table 1.** The RMN results for amoxicillin photodecomposition and byproducts [11].

detection in the environment is difficult. The development of analytical technique allows the identification and quantification of the ampicillin and ampicillin degradation by-products as 2-hydroxy-3-phenylpyrazine (HPP) in the environment. The results indicate their presence in 42–79% of the monitored rivers and household ponds but they were not detected in aquaculture ponds. In these locations, the HPP concentrations were in the range of 1.3–413.3 ngL−1.The research results indicate the HPP presence as a promising marker for AMP presence and other β-lactam antibiotics with AMP substructure into the environment [22, 24, 25] (**Figures 5** and **6**).

**Figure 5.** Amoxicillin chemical structure.

The β-lactams antibiotics such as ampicillin, penicillins, cephalosporins, and oxicephalosporins inhibit biosynthesis of the bacterial cell wall by acylating and thereby inactivating transpeptidases. The antibacterial activity depends on the β-lactams rings, and some complex

**Figure 6.** The photodecomposition scheme for ampicillin and its by-products.

**Figure 7.** The complex formation with Cu-ampicillin chemical structure as a complex ligand.

**Figure 5.** Amoxicillin chemical structure.

(**Figures 5** and **6**).

detection in the environment is difficult. The development of analytical technique allows the identification and quantification of the ampicillin and ampicillin degradation by-products as 2-hydroxy-3-phenylpyrazine (HPP) in the environment. The results indicate their presence in 42–79% of the monitored rivers and household ponds but they were not detected in aquaculture ponds. In these locations, the HPP concentrations were in the range of 1.3–413.3 ngL−1.The research results indicate the HPP presence as a promising marker for AMP presence and other β-lactam antibiotics with AMP substructure into the environment [22, 24, 25]

**Hydrogen AMX ADP1 ADP2 ADP3 ADP4 ADP5 ADP6 ADP7 ADP8** CH3 136 0.95 1.33 1.20 1.37 1.26 131 1.28

H-4 4.09 3.97 3.67 4.31 4.00 4.09 3.69 3.69 H-17 5.07 5.18 5.10 4.99 5.09 5.09 4.91 4.95 H-2 5.44 5.17 5.37 5.25 4.95 5.05 5.17 5.15 H-6a 5.44 5.18 4.46 5.90 3.54 3.70 3.90 4.39

H-21,23 6.92 6.96 6.96 6.94 6.96 6.96 6.81 6.82 6.82 H-20,24 7.31 7.40 7.40 7.31 7.35 7.35 8.13 7.18 7.18

H-6b 3.87 3.83

88 Emerging Pollutants - Some Strategies for the Quality Preservation of Our Environment

ADP6 7.24 ADP6 7.45

**Table 1.** The RMN results for amoxicillin photodecomposition and byproducts [11].

1.37 1.53 1.39 1.57 1.53 1.62 1.65 1.66

compounds are responsible for their deactivation. There are several possible sites of the coordination for the metal ions on penicillin. The nitrogen and the double oxygen bonding are the most probable [13, 24, 26].

attractive. Two or more antibiotics always coexist in the polluted aquatic environment. Thus,

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Published works related a variety of antibiotics in polluted soil and water environment. Therefore, it is of great significance to explore the ecological risk of the combined exposure to various antibiotics. The mixture of different types of antibiotics may lead to varying joint

Some published works indicate that antibiotics mixtures present synergetic effects and others antagonistic effects. The presence of sulfonamides (SA), as potentiator effects (SAP), and tetracycline's (TC) was investigated for binary and tertiary mixture toxicity. The mixtures of SA-SAP and SA-SAP-TC presented a synergetic impact on bacteria tests, while SA-TC and SAP-TC showed antagonistic effects. The TC presence in ternary mixtures altered the toxic ratio of SA and SAP, which lead to the various joint effects of the ternary mixtures on different

Since the beginning, the powder biocarbon in Brazil was considered a worthless material, always related to airborne pollution, infant and slavery condition work, and work-related disease. Nowadays, a group of researchers is trying to restore the biocarbon industrial use as an essential additive for agroindustry on soil amendment with possibility of enhancing the

The biocarbon (biochar) has been used to increase the amount of organic matter in the agricultural soil. There are many benefits in this application, resulting in improved soil fertility, nutrient content, water retention, better physical structure, and improved microbial activity. Intense agricultural operation tends to reduce the amount of organic matter present in

The application of biocarbon can be decisive in the semi-arid region of the northeast region with low rainwater retention, and such water source is scarce and used in a short period of the year. Soon, the agriculturists of these areas will be able to produce the own bio-carbon

The biocarbon organic matter composition allows its use as a slow-release fertilizer such as adsorbent properties promoting the addition, retaining and the release of nutrients. The addition of some plastic agents like stack gel and bentonite clay helps the nutrient releasing rate control during the pellets formation. The biocarbon is a renewable organic matter source and provides phosphate and nitrate from wastewater adsorption treatment with nutrient reten-

Biocarbon produced in a high-temperature pyrolysis application on heavy metals retention such as cadmium and zinc is studied. In some cases, it has been used in the recovery of soils with different levels of cadmium, zinc, and leads contaminated by the mining industry,

it is essential and meaningful to discuss the multicomponent antibiotics solution.

effects on the bacteria's, synergistic, additive, and some antagonistic effects.

bacteria populations.

the soil.

**5. The biocarbon: adsorbent uses**

organic matter and water content retention.

utilizing the agriculture biomass.

tion for further agriculture use as slow-release fertilizer.

reducing the concentration of toxic metals in plants such as beans.

The amoxicillin and many antibiotics can act as a complex ligand with several possible sites for metal ions like Cu (II), Zn (II), and Cd(II) for coordination on penicillin. In the study, the kinetics and thermodynamics calculations are easy to find and how the neighboring group affects the probable complexation sites, of metals and the C=O of the antibiotic β-lactamic group and the NH amido penicillin group. The two most probable structures are shown in **Figure 7**. They are not excluding each other. For cephalexin and Cu2+, the interaction takes place through the side chain, the same as expected for ampicillin structure.

The metal ligand binary constants at temperature 37°C and ionic strength for ampicillin and Co2+ are = 3.12, for Ni2+ = 3.66, for Cu2+ = 4.79 and for Zn2+ = 2.98. Usually, the complex constants with Cooper are more stable [14, 23].
