1 Introduction

Human activities appear to be the major contributor to water pollution, for instance, agricultural, industrial, and municipal activities (Rashed & Arfien, 2020). Ammonia was found in industrial wastewater in high rate as a result of use it in industry fields such as agriculture fertilizers, plastic productions, and explosives (Dr. Rakesh Govind, 2017; Kim et al., 2010). Wastewater comes from manufactories, agriculture drainage, homes, and ground waters that contain usually ammonia (NH3+) and nitrogen derivatives.

Over 2 × 1011 kg of ammonia is produced globally per year by the Haber–Bosch process which combines molecular hydrogen and nitrogen to synthesize ammonia as reported by Bock (2016). Most is used for fertilizer and agriculture while the remaining is used for other purposes including industrial processes and explosives (Bock, 2016; Madeira et al., 2020). Ammonia percentage from total nitrogen (TN) in wastewater is 40–50% (Guštin & Marinšek-Logar, 2011; Bernal et al., 2016). The excessive amount of ammonia presents in water streams has led to serious potable water scarceness worldwide. The existence of these contaminants in drinking water is toxic to human (Karadag et al., 2006; Taddeo et al., 2017; Wu et al., 2008). Therefore, it was necessary to find novel methods and economically at the same time for removal of ammonia and the contaminants present in the water. Indeed, many researchers have begun to investigate and work on removal of ammonia and many other types of contaminants in the past. The application of conventional methods in removing ammonia suffers from many drawbacks (Adam et al., 2019). Therefore, several methods were used to remove ammonia such as biological nitrification, air-stripping, ion exchange, and adsorption. The biological nitrification–denitrification process is a widely used method in ammonia removal (Junaidi & Sitinjak, 2020; Kuai & Verstraete, 1998). Phytoremediation has been used as environmentally friendly and effective methods, such as using Pistia stratiotes to remove NH4+ from water and Eichhornia crassipes to remove nitrate (Pourfadakari & Enayat, 2023). However, such process is not appropriate for industrial wastewater, because it contains high value of ammonia (Lee et al., 2000; Simm et al., 2006). Other methods are suitable in case of high ammonia content (Karri et al., 2018), such as precipitation (Quan et al., 2010), breakpoint chlorination (Zaghouane-Boudiaf & Boutahala, 2011), air-stripping (Hasanoĝlu et al., 2010; Limoli et al., 2016; Liu et al., 2015), ion exchange (Jorgensen & Weatherley, 2003; Rahmani et al., 2004), and adsorption (Cheng et al., 2019; Santoso et al., 2020; Seruga et al., 2019). Adsorption is a surface phenomenon that occurs by an adsorbent that attracts pollutant atoms to the surface of its molecules (Cai et al., 2019; Soliman et al., 2023). Several previous studies presented this technique and studied adsorbent efficiency (Erdoǧan & Ülkü, 2011). Chemical and engineering researchers dealt with the use of activated carbon as adsorbent and tried to develop its performance (Anfar et al., 2020). For example, zeolite was used as adsorbent medium for ammonia removal (Huang et al., 2010, 2015). Another study used bentonite as adsorbent and reached to accepted results (de Luna et al., 2018; Malamis & Katsou, 2013; Mohajeri et al., 2018). Biochar as adsorbent is cheaper and simpler to produce than activated carbon; it does not need any chemicals as some types of activated carbon (Kinnunen & Laurén, 2023). Its ability to adsorb metals and decrease acidity in soil drainage water has been studied (Kinnunen et al., 2021). Likewise, the use of metal oxides such as nickel oxide in the adsorption process (gomaa et al., 2021). It is worth noting that natural minerals may have high cost and are exposed to annihilation. Furthermore, synthetic minerals need difficult conditions to be produced, so the need for adsorbent medium generally appears. Metakaolin geopolymer MK-GP was used by researchers for work as adsorbent in ammonia removal (Luukkonen et al., 2016, 2017, 2018; Samarina & Takaluoma, 2019) and tried to optimize MK-GP preparation for achieving the best efficiency. The efficiency of titan yellow (TY) supported on thiourea-formaldehyde resin (TF) was studied, and it is found efficient for Mg(II) removal with adsorption capacity of 19.45 mg g−1 (Elwakeel & Arabia, 2020). This study presents a preparation of a new adsorbent medium, its characterization, and work efficiency. In the current work, novel adsorbing materials (oxide glasses) are used for removing ammonia and nitrogen derivatives. The presence of dangling bond defects in oxide glasses makes them strong candidates for adsorption process. Based on the glass oxide former, there are four common types of oxide glasses including borate (B2O3) glasses, phosphate (P2O5) glasses, silicate (SiO2) glasses, and germinate (Ge2O3) glasses. A large amount of ammonia and other contaminant molecules or atoms can be attracted and pulled by the banding bond defects in the oxide glasses. Glasses were made by man from 4000 years; its structure was potentially studied only in the 1920s after X-ray diffraction (XRD) technique development as reported by Vedishcheva and Wright (2014). Oxide glass properties make them useful in many applications and suitable for solving special problems (Axinte, 2011). Glasses have amorphous form (Axinte, 2012) and are formed by the conventional melt quenching technique to solid case without crystallization (Camilo et al., 2013; Jiménez et al., 2011). Glass formation needs critical cooling rates, depending on the chemical composition of the glass (Yadav & Singh, 2015). The aim of the present study is to investigate the efficiency of some oxide glasses (as adsorbing materials) with different glass formers in removing contaminants from wastewater. The chemical compositions of these glasses with mole percent (mol%) are 45 GFO–5 CuO–5 Al2O3–45 Na2O; GFO (glass-forming oxide) is B2O3, P2O5, SiO2, and GeO2, respectively. The amorphous nature of such glasses is confirmed by XRD analysis (Ahmed et al., 2022). The influence of important parameters including temperature, contact time, and initial adsorbent dosage on the adsorption process is also demonstrated.

2 Materials and Methods

2.1 Materials and Wastewater

  • Boron oxide (98%), silicon oxide (99.5%), germanium oxide (99.9%), phosphor oxide (99%), aluminum oxide (99.9%), copper(II) oxide (99%), and sodium carbonate (99.5%) were obtained from Alfa Aesar. Alfa Aesar is a leading manufacturer and supplier of chemicals for scientific applications and researches.

  • Wastewater was used as a sample in this study; it was collected from the drainage of agricultural fertilizer manufactory and chemical industry at the first experiment, which was collected 1 day before the experimental work. Synthetic samples have been used in the subsequent experiments, which have the same properties of manufactory sample, in order to save the same conditions in all experiments. The wastewater samples have been collected or synthesized 1 day before adsorption experiment, and the samples were kept at 5 °C to experimental time (Torfs et al., 2016).

2.2 Adsorbent (Oxide Glass) Preparation and Characterization

Oxide glasses were prepared in this experimental work by the conventional melt quenching technique. The chemical composition quantity in each oxide glass system was measured depending on its molecular weight by Eq. (1):

$$The\;quantity\;of\;oxide=\frac{M.W. \times P}F$$
(1)

M.W. is the molecular weight of each component; it was calculated from the molecular weight of each chemical element in the periodic table, P is the percentage of the component in glass composition. F is a factor used to make component value applicable.

The prepared glasses have the chemical formula of 45 GFO–5 CuO–5 Al2O3–45 Na2O; GFO (glass forming oxide) is B2O3, P2O5, SiO2, and GeO2, labeled A, B, C, and D, respectively. Sodium carbonate is used as a precursor of Na2O for reducing the melting point. Hybrid borate and silicate (borosilicate) glasses with the chemical composition of 25 B2O3–20 SiO2–5 CuO–5 Al2O3–45 Na2O (labeled E) are also prepared. After determination of the weight of each component in composition of each type of oxide glass, all components of one glass type were mixed and milled together in porcelain mill. Porcelain crucible has been used to contain the mixture, and then it was put in a muffle furnace at 1000 °C for 1 h. Once the melt comes out from furnace to room temperature, the glass is formed as a piece with its properties. Grinding machine was used to grind glass pieces to small particle size, and then particles were sieved. The particle size obtained in this study was 63–125 µm. A structural composition of oxide glasses used was investigated by X-ray diffraction analysis (XRD) to confirm the amorphous structure of the prepared glasses.

2.3 Wastewater Sample Preparation and Characterization

Wastewater samples used in this study were made by adding required quantity of ammonium hydroxide NH4OH and ammonium nitrate NH4NO3 into drinking water; this is to simulate the same total nitrogen (TN), ammonia (NH3+), and nitrate (NO3) values in the initial sample of industrial wastewater. Table 1 explains the properties of wastewater samples. Analysis was carried out according to Standard Methods (APHA, 2002; Federation 1999).

Table 1 Properties of collected or synthesized wastewater samples
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2.4 Adsorption Process

The processes were run to determine the efficiency of each oxide glass in total nitrogen, ammonia, and nitrate removal. All oxide glasses were examined in the adsorption process at the same boundary conditions. Then, the influence of boundary conditions of adsorption process is studied. The initial dosage of adsorbent was 0.75 mg to each 100-ml wastewater sample. Then, the mixture of the sample and the oxide glass dosage was stirred at 300 rpm for 60 min at 40 °C. The sample was filtrated after stirring by Buchner funnel. Filter paper used was qualitative filter paper. After adsorption process, the samples were kept at 5 °C to analysis time. Spectrophotometer was used for parameter sample analysis. Analysis is carried out to estimate the value of removal efficiency and adsorption capacity of each used oxide glass. Figure 1 summarizes experimental setup steps. Adsorption capacity is the unit weight of contaminant quantity which is adsorb on per gram of used adsorbent.

Fig. 1
figure 1

Experimental setup step summary

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Oxide glass removal efficiency (E%) and its adsorption capacity (Qt) of the investigated contaminants (adsorbate) were calculated by Eqs. (2) and (3) respectively:

$$E\%=100 \frac{{C}_{0}-{C}_{f}}{{C}_{o}}$$
(2)
$$Qt= \frac{{C}_{0}-{C}_{t}}{V}/ m$$
(3)

C0 is the initial concentration of adsorbate (mgA/L), Ct is the concentration of adsorbate (mgA/L) at time t, Cf is the final concentrations of adsorbate (mgA/L), V is the volume of wastewater sample (L), m is the adsorbent mass (g), and Qt is adsorption capacity of adsorbate per gram of oxide glass (mgA/gG) at a time t.

3 Results and Discussion

3.1 XRD Analysis of As-Prepared Glasses

X-ray diffraction analysis (XRD) is carried out for all oxide glasses (adsorbents) using Bucker D8 Advance Diffractometer in the two theta range from 10° to 80°. Figure 2 shows the XRD pattern of adsorbents. It is observed that no crystalline peaks appeared in all XRD patterns, indicating the amorphous nature of all glasses.

Fig. 2
figure 2

X-ray diffraction pattern of oxide glasses (adsorbents)

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3.2 Water Treatment (Adsorption Process)

Oxide glasses are composed of the former cations embedded in an oxygen network. The incorporation of modifier cations into the glass network breaks the linkages between former cations and oxygen anions and forms vacant cavities for other doping ions (contaminants in the wastewater). Addition of modifiers causes a formation of non-bridging oxygen groups by disrupting the glass network (Sołtys et al., 2018). Furthermore, modifiers play a vital role in the creation of the dangling bonds and non-bridging oxygen (NBOs) (Ramesh Babu & Yusub, 2020). The presence of the dangling bonds and NBOs is strongly beneficial for adsorption process, and their numbers depend on the kind of glass former and glass modifier as well as their concentration. In the following, we will report the influence of contact time, adsorption temperature, and adsorbent dosage on the contaminant removal efficiency.

3.3 Effect of Oxide Glass Chemical Composition

Here, we investigate the effect of glass former variation on the contaminant removal to determine the glass type, giving optimum efficiency. The most common oxide glasses including borate A, phosphate B, silicate C, and germinate D glasses (with the above mentioned chemical compositions) are used as adsorbing materials. The influences of each on the total nitrogen TN, ammonia NH3+, and nitrate No3 removal efficiency are depicted in Fig. 3. It is observed that lower efficiencies are detected for the phosphate and germinate glasses, as the removal efficiency of total nitrogen, ammonia, and nitrate is around 48%, 29%, and 17%, respectively, for phosphate glass and around 44%, 20%, and 2%, respectively, for germinate glass. While borate and silicate glasses exhibit the highest removal efficiency, as the removal efficiency of total nitrogen, ammonia, and nitrate is around 53%, 37%, and 31%, respectively, for borate glass and around 52%, 33%, and 32%, respectively, for silicate glass. This may indicate that the tendency of borate and silicate glasses to form dangling bonds and non-bridging oxygen by network modification is higher than that of phosphate and germinate glasses. Perhaps another reason is that the surface area of borate and silicate glasses is larger than that of phosphate and germinate glasses that leads to larger active sites, which can adsorb contaminant molecules by larger quantity (Coulombe et al., 2023; Yang et al., 2023). Therefore, it is suggested to add a hybrid borate and silicate glass (borosilicate glass) in the adsorption treatment process.

Fig. 3
figure 3

TN, NH3+, and NO3 removal efficiency of oxide glass types

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3.4 Effect of Boundary Conditions

Boundary conditions are of great importance, not less than the importance of adsorbent used type, as they have an impact on the efficiency of adsorption process, even if it has been covered in many previous studies. In this study, some boundary conditions were surveyed, and their impact on the performance of adsorption process was studied.

3.4.1 Effect of Contact Time

Based on the above investigation for determining the glass formers giving best adsorption performance, three glass compositions are used to study the dependence of contaminant removal efficiency on the adsorption contact time. These glasses are borate (A), silicate (C), and borosilicate (E) glasses. Studies have been done in same boundary condition dosage of 0.75 mg/100ml and temperature of 40 °C except contact time. The effect of contact time is investigated using five periods including of 30, 60, 90, 120, and 150 min. The performance of borate, silicate, and borosilicate glass in the adsorption process in different contact times is depicted in Fig. 4.

Fig. 4
figure 4

TN, NH3+, and NO3 removal efficiency of different adsorbents (A: borate glass, C: silicate glass, and E: borosilicate glass) in different contact times

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Dependence of the concentration and removal efficiency data of total nitrogen, ammonia, and nitrate on the contact time ranging from 30 to 150 min is depicted in Fig. 4. The figure shows the different performances of oxide glass types in different contact time periods. In Fig. 4a, it is observed that borosilicate glass gives the best efficiency in removal of total nitrogen compared to other glasses. In addition to total nitrogen removal, the efficiency of borosilicate glass is getting improved over the time of examination; it is 50% at 30 min and reaches 60% at 150 min, which attributed to active sites in the surface area of borosilicate glass attracting nitrogen molecules by more power with time. Total nitrogen removal efficiency of borate glass is increasing slowly from around 49% at 30 min to around 51% at 120 min, then decreasing from around 51% to around 45% at 150 min. In case of silicate glass adsorbent, total nitrogen removal efficiency is increasing from around 49% at 30 min to around 54% at 120 min, and then it is decreases to around 49% at 150 min. It is possible that this behavior is due to the saturation of active sites with nitrogen molecules, which leads to a decrease in its efficiency (Zhao et al., 2016). Haldorai et al. (2015) reported that the removal efficiency is decreasing with contact time increasing due to desorption after equilibrium point. Silicate glass sample exceeds ammonia removal as shown in Fig. 4b; ammonia removal efficiency is increasing from around 34% at 30 min to around 50% at 150 min. The efficiency of borate glass and borosilicate glass is close in ammonia removal; ammonia removal efficiency is around 33% and 36% at 30 min and around 45% and 46% at 150 min for borate glass and borosilicate glass adsorbents, respectively. That means the adsorption capacity of ammonia on silicate glass is higher than that on borate and borosilicate glasses that may be attributed to the power of active sites in the silicate glass surface area to attract ammonia molecules stronger than it in borate and borosilicate glass. Another explanation is that active sites that are ready to receive ammonia molecule and which turn into occupied sites in silicate glass are higher than those in the surface area of borate and borosilicate glasses. It is worth observing that the ammonia removal efficiency increases with contact time rising, that with three types of the glasses. It was concluded that the relation between ammonia removal efficiency and contact time is direct, regardless of adsorbent structure. As pointed in previous study (Alshameri et al., 2014; Seruga et al. 2019), the ammonia removal efficiency increases with adsorption time prolongation. Figure 4c shows nitrate removal efficiency of borate glass increasing from around 34% at 30 min to around 39% at 90 min, and then it decreased to around 37% and 33% at 120 and 150 min respectively. Nitrate removal efficiency of silicate glass increases from 36% at 30 min to around 38% at 120 min, and then it is decreases to 36% at 150 min, and it is observed that the increase and decrease are slowly over the time of examination. That attributed to the nitrate removal efficiency attained the equilibrium point after contact time of 90 min (Ashour et al., 2017). The nitrate removal efficiency of borosilicate glass decreases over the time of the adsorption process. It is around 39% at 30 min and reached to 40% at 60 min and then started to decrease till around 38% at 150 min; it might be that nitrogen dissolved in water was oxidizing and then turned into nitrates, after 60 min of adsorption with borosilicate glass. In another point of view, the behavior is attributed to desorption after 60 min (Haldorai et al., 2015) or reaching to equilibrium in 60 min (Zhao et al., 2016). The best removal efficiency of nitrate was achieved with adsorbent borosilicate, as shown in Fig. 4c. In most cases, the removal efficiency of borosilicate glass was better. In some cases, other adsorbents exceed, but the difference was very little. In most cases, the removal efficiency of total nitrogen and nitrate decreased at time 120 min, efficiency was close at 90 min and at 120 min whether by increase or decrease. In a few cases, the time 120 min gives removal efficiency higher than at 90 min, but with very little difference. The superiority was mostly in favor of the contact time 90 min.

3.4.2 Effect of Temperature

After determining the best adsorbent composition (borosilicate glasses) and contact time (90 min) that give the proper removal performance, the effect of adsorption temperature on contaminants removal will be investigated. The temperature effect on total nitrogen, ammonia, and nitrate using the borosilicate glass as adsorbent at constant contact time 90 min is depicted in Fig. 5.

Fig. 5
figure 5

Effect of temperature on TN, NH3+, and NO3 removal efficiency

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It is observed from Fig. 5 that total nitrogen removal efficiency was around 56% at 30 °C; it increased to around 63% at 70 °C. Ammonia removal efficiency appeared in Fig. 5; it is around 34% at 30 °C; it increased to around 53% at 70 °C. The similar trend appeared for nitrate removal efficiency; it is around 32% at 30 °C; it is increasing to around 46% at 70 °C. It is observed that the temperature had a direct effect on total nitrogen, ammonia, and nitrate removal by borosilicate glass adsorbent. This means that the solution temperature mainly influences on the expansion nature of adsorbent and decreases the thickness of its boundary layer, thus reducing the resistance of interacting adsorbate ions with adsorbent active sites (Iftekhar et al., 2018a, b). Other studies indicated that removal efficiency improvement with temperature increasing implies that the adsorption is an endothermic chemical process (Moussavi et al., 2011; Zheng et al., 2008). Another explanation is reported in a previous study (Alkan et al., 2008); temperature increasing leads to a decrease in water viscosity, which leads to an increasing in the spread rate of adsorbate molecules in addition to supplying them with the energy needed to increase their interaction with active sites on the surface area of adsorbent. Therefore, a temperature of 70 °C is chosen to study the effect of the adsorbent dosage.

3.4.3 Effect of Adsorbent Dosage

The effect of borosilicate glass dosage in the range 0.25–1.5 g/100ml was examined on adsorption efficiency of total nitrogen, ammonia, and nitrate, and the results are depicted in Fig. 6, with contact time of 90 min and temperature of 70°C.

Fig. 6
figure 6

Effect of the glass dosage on TN, NH3+, and NO3 removal efficiency

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As shown in Fig. 6, the increase in adsorbent dosage leads to improvement of adsorption process efficiency. It is attributed to the fact that increased adsorbent dose leads to an increase in active sites in adsorbent surface area, which in turn leads to increase in contaminant molecule adsorption (Iftekhar et al., 2018a, 2018b). At this study, initial concentration of total nitrogen, ammonia, and nitrate was 361 mg/l, 170.6 mg/l, and 169.9 mg/l, respectively. As shown in Fig. 6, in the case of adsorbent dosage 0.25 g/100 ml, the removal efficiency of total nitrogen, ammonia, and nitrate reached to 49.86%, 28.546%, and 23.719% respectively. Figure 6 shows that the removal efficiency is increasing with increasing adsorbent dosage; it reached to around 84%, 80%, and 64% for total nitrogen, ammonia, and nitrate respectively, in the case of adsorbent dosage 1.5 g/100 ml. Previous studies reported the same behavior with increasing removal efficiency with adsorbent dosage; they pointed that it was attributed to adsorption increasing following the increase in the dosage of adsorbent due to availability of adsorbent active sites (Das & Das, 2013; Esposito et al., 2001; Xie et al., 2015). One of the studies (Kütahyali et al., 2010) found that the adsorption performance improved with the increased adsorbent dosage. They used different dosages of Pinus brutia leaf, which was used as an adsorbent material in the study. The dosage was extended from 0.05 to 0.45 g, and they reported that the increase in the removal efficiency is achieved with the increase in adsorbent dosage. In another study, it was observed the optimum adsorption results reported when using the highest dose of adsorbent (Gasser & Aly, 2013). Researchers reported that MgFe-LDH-CYanex72 and hydroxyapatite achieved the best adsorption results with 10 g/l dosage.

3.5 Adsorption Isotherms

Adsorption isotherms are necessary to describe the interaction of contaminant concentration with borosilicate glass, and they are important to improve the use of adsorbent. Therefore, empirical equations (Langmuir and Freundlich isotherm model) are essential for explanation of adsorption data. Both Langmuir and Freundlich models were used to evaluate the adsorption process and explain the data of equilibrium isotherm (Armbruster & Austin, 1938). The Langmuir theory (monolayer adsorption — Eq. 4) is based on assumptions:

  1. 1.

    Dynamic equilibrium (rate of desorption is the same of adsorption rate at equilibrium point)

  2. 2.

    Surface of adsorbent material is homogenous

  3. 3.

    Neglect the interaction between adsorbate molecules and adsorbent surface

    $$\frac{{C}_{t}}{{Q}_{t}}= \frac{1}{{K}_{eq}}+ \frac{{C}_{t}}{{Q}_{max}}$$
    (4)

Freundlich theory supports that the adsorbent surface is not homogenous (Eq. 5). The theory works on the assumption that adsorption sites of adsorbent surface have different adsorption energy.

$$\mathrm{log\;}{Q}_{t}=\mathrm{ log }{K}_{F} + \frac{1}{n }\mathrm{log}{C}_{t}$$
(5)

The parameter Keq is Langmuir constant; the parameters KF and n are Freundlich constants; Ct is the adsorbate concentration at time t (mg/l); Qt is the adsorption capacity at time t (mg/g); Qmax is the maximum adsorption capacity (mg/g).

The results from contact time study were analyzed by Langmuir and Freundlich isothermal adsorption models. The linear plot of Langmuir and Freundlich is shown in Figs. 7 and 8 respectively, and the adsorption data of both isotherm models determined from the slope and the intercept of the plots are collected in Table 2.

Fig. 7
figure 7

Linear plot of Langmuir isotherm of TN, NH3+, and NO3 on borosilicate glass

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Fig. 8
figure 8

Linear plot of Freundlich isotherm of TN, NH3+, and NO3 on borosilicate glass

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Table 2 Fitted parameters determined for the adsorption isotherms
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As show in Figs. 7 and 8 and Table 2 data, the data from experimental work correspond to the Langmuir and Freundlich model linear form as well. That means the adsorption process can be carried out chemical or physical for borosilicate glass.

3.6 Adsorption Capacity of Ammonia on Adsorbent

In this study, the maximum adsorption capacity of ammonia reached to 9.12 mg/g with adsorption contact time of 90 min, temperature of 70°C, initial concentration of ammonia of 170.6 mg/l, and borosilicate glass dosage of 1.5 mg/100ml, where the ammonia concentration reached to 33.8 mg/L in solution sample after the adsorption process is finished (Eq. 3). The adsorption capacity is considered a measure of adsorbent efficiency, but after adsorption capacity, saturation is the start of desorption and instability (Cheng et al., 2019). The adsorption capacity of ammonia in the current study was compared with previous studies in Table 3; to explain the efficiency of borosilicate glass compared to others, adsorbents were used in previous studies. The adsorption capacity value of this study is superior and accepted compared with some studies, but other studies have outperformed, attributed to that the initial concentration of ammonia is less than in this study or adsorbent is stronger in attracting contaminant molecules.

Table 3 Comparison between current study and previous studies
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4 Conclusions

The findings of this study pointed that borosilicate glass with AL2O3 (as a glass co-former) and CuO (as a glass network modifier) achieved noteworthy success in adsorption process. The boundary conditions affect adsorption process performance such as contact time, temperature, and adsorbent dosage.

  1. 1.

    Total nitrogen removal efficiency increased with increasing contact time when borosilicate glass is used. In the case of using borate and silicate glasses, total nitrogen removal efficiency is increased until contact time reaches 120 min, then it exhibits a decreasing trend. Moreover, the total nitrogen removal efficiency increases with increasing adsorption process temperature and adsorbent dosage.

  2. 2.

    Ammonia removal efficiency is improved with increasing contact time when using borate glass, silicate glass, or borosilicate glass as adsorbent. Ammonia removal efficiency is also enhanced by increasing temperature and adsorbent dosage.

  3. 3.

    Nitrate removal efficiency is approximately constant with increasing contact time when the used adsorbent is silicate glass. In case of borate glass and borosilicate glasses, it is improved until contact time reaches 90 min, and then it got worse. Nitrate removal efficiency is increased with temperature and adsorbent dosage increasing.

  4. 4.

    To get effective adsorption process, the appropriate contact time is 90 min when adsorbent was borosilicate glass.

  5. 5.

    Performance of adsorption process with borosilicate glass adsorbent increasing with temperature increasing until 70 °C.

  6. 6.

    Performance of adsorption process increases with increasing borosilicate glass dosage until 1.5 mg/l. It is recommended to study the behavior with dosages more than 1.5 mg/l.