Preparation of Activated Carbon from the Wood of Paulownia tomentosa as an Efficient Adsorbent for the Removal of Acid Red 4 and Methylene Blue Present in Wastewater

Study on the structure characterization and swelling properties of the Fe3O4/CMS composite membrane

In order to improve the functionality of cellulosic materials research and development of high performance soluble materials. Therefore, the Fe3O4/CMS composite membrane was prepared by using carboxymethyl salix powder (CMS) and Fe3O4 as raw materials, 1-propenyl-3-methylimidazolium chloride and dimethyl sulfoxide as dissolution system. The effects of swelling time, swelling temperature, pH and ionic strength on the swelling performance of Fe3O4/CMS composite membranes and the swelling kinetics of the composite membranes were studied. The structure of the composite membrane was characterized by SEM, FT-IR, XRD and TG. The results showed that the swelling degree reached 5.54 g·g-1, when the swelling time was 45 min, the swelling temperature was 65°C, the pH was 5 and the ionic strength was 0.08 mol·L-1. The initial phase of dissolution of the composite membrane fits well with the Fickian diffusion model, and the whole dissolution process belongs to the Schott model, indicating that the main role of the dissolution process is the diffusion of water molecules, while the composite membrane can be preserved for a long time at high temperature, which provides sustainability for the composite membrane. The characterization results showed that the surface of Fe3O4/CMS composite film was rough with small grooves. The O-H effect was enhanced and the Fe-O absorption peak appeared at 600 cm-1, indicating that Fe3O4 had been successfully loaded onto the cellulose membrane. The Fe3O4/CMS composite membrane belonged to cellulose type II structure, meanwhile, the composite membrane had good thermal stability.

Exploring the superior adsorption capacity of multi-layer graphene/alginate granules for the removal of methylene blue dye from water

Graphene-based materials are gaining increasing attention towards their use in manufacturing and environmental applications. In this context, multi-layer graphene (MG) has been recently applied for the adsorption of contaminants from water resulting in promising results. However, the extreme lightness of this material often makes it difficult to handle due to its potential dispersion in the surrounding environment as well as to its transport and loss with the effluent. In this study, a novel granular material was synthesized by embedding MG into an alginate matrix, resulting in the so-called granular MG (GMG). This material was tested for the adsorption of methylene blue (MB) from water, which is a typical dye used in textile industries and must be removed from the effluent. GMG materials with different MG contents (5 and 20 %) were compared with MG and a commercial adsorbent to assess their adsorption capacity and the most performing material was selected for in-depth physical and chemical characterization. The structural, surface, kinetic, isotherm, and thermodynamic properties, the pH and temperature dependence, as well as the regeneration and reuse of GMG 5% were investigated through batch adsorption tests under different operating conditions. The study reveals that GMG 5% has a superior adsorption capacity compared to the tested materials and can be considered as a promising alternative to commercial carbon-based materials according to techno-economic considerations.

Biomass-based activated carbons produced by chemical activation with H3PO4 as catalysts for the transformation of α-pinene to high-added chemicals

In the era of ecology and careful care for the environment, it becomes important to use renewable raw materials of plant origin, which are often more easily available and cheaper. One of the important and rapidly developing directions of research are works related to the use of waste plant biomass; an example of this trend is the production of activated carbons from food industry waste. One of the examples of the application of derived from biomass activated carbons can be using them as catalysts for the isomerization of terpene compounds. Carbons based on waste biomass are characterized by the minimal amount of waste formation during their manufacture, and their use in the isomerization reaction allows to obtain high conversion of organic raw material and high selectivities of transformation to the desired products, making these carbons environmentally friendly substitutes for the catalysts used usually in this process. In this work, obtained carbonaceous catalysts were tested in the process of isomerization of α-pinene to high value chemicals (mainly camphene and limonene). Under the most favorable conditions (activated carbon from sunflower husks content in reaction mixture 5 wt%, temperature 180 °C, and reaction time 100 min), α-pinene was completely converted (conversion 100 mol%) with high selectivity towards camphene (54 mol%). To prepare activated carbons, biomass precursors (orange peels, sunflower husks, spent coffee grounds) were activated with 85% H3PO4 through the chemical activation. The obtained materials were characterized by such methods as sorption N2 at - 196 °C, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and X-ray fluorescence (XRF) to determine the relationship between their textural-chemical properties and catalysts activity in isomerization process. The synthesized materials were characterized by a specific surface area in the range of 930-1764 m2, total pore volume in the range of 0.551-1.02 cm3/g, and total acid-site concentrations in the range of 1.47-2.33 mmol/g. These results showed that textural parameters of the obtained activated carbons have the important role in the isomerization of α-pinene.

Optimization of hydrothermal synthesis conditions of Bidens pilosa-derived NiFe2O4@AC for dye adsorption using response surface methodology and Box-Behnken design

The presence of stable and hazardous organic dyes in industrial effluents poses significant risks to both public health and the environment. Activated carbons and biochars are widely used adsorbents for removal of these pollutants, but they often have several disadvantages such as poor recoverability and inseparability from water in the post-adsorption process. Incorporating a magnetic component into activated carbons can address these drawbacks. This study aims to optimizing the production of NiFe2O4-loaded activated carbon (NiFe2O4@AC) derived from a Bidens pilosa biomass source through a hydrothermal method for the adsorption of Rhodamine B (RhB), methyl orange (MO), and methyl red (MR) dyes. Response surface methodology (RSM) and Box-Behnken design (BBD) were applied to analyze the key synthesis factors such as NiFe2O4 loading percentage (10-50%), hydrothermal temperature (120-180 °C), and reaction time (6-18 h). The optimized condition was found at a NiFe2O4 loading of 19.93%, a temperature of 135.55 °C, and a reaction time of 16.54 h. The optimum NiFe2O4@AC demonstrated excellent sorption efficiencies of higher than 92.98-97.10% against all three dyes. This adsorbent was characterized, exhibiting a well-developed porous structure with a high surface area of 973.5 m2 g-1. Kinetic and isotherm were studied with the best fit of pseudo-second-order, and Freundlich or Temkin. Qmax values were determined to be 204.07, 266.16, and 177.70 mg g-1 for RhB, MO, and MR, respectively. By selecting HCl as an elution, NiFe2O4@AC could be efficiently reused for at least 4 cycles. Thus, the Bidens pilosa-derived NiFe2O4@AC can be a promising material for effective and recyclable removal of dye pollutants from wastewater.

Advances in understanding entire process of medium chain carboxylic acid production from organic wastes via chain elongation

Chain elongation is an environmentally friendly biological technology capable of converting organic wastes into medium chain carboxylic acids (MCCAs). This review aims to offer a comprehensive analysis of MCCA production from organic wastes via chain elongation. Seven kinds of organic wastes are introduced and classified as easily degradable and hardly degradable. Among them, food waste, fruit and vegetable waste are the most potential organic wastes for MCCA production. Combined pretreatment technologies should be encouraged for the pretreatment of hardly degradable organic wastes. Furthermore, the mechanisms during MCCA production are analyzed, and the key influencing factors are evaluated, which affect the MCCA production and chain elongation efficiency indirectly. Extracting MCCA simultaneously is the most important way to improve MCCA production efficiency, and technologies for sequentially extracting different kinds of MCCAs are recommended. Finally, some perspectives for future chain elongation researches are proposed to promote the large-scale application of chain elongation.

Production of AC from Bamboo, Orange, and Paulownia Waste-Influence of Activation Gas and Biomass Maturation

The production of agricultural waste is associated with environmental problems and risks to public health. The general interest demands, as an ecological alternative, the proper management of waste generated by industrial activity through its transformation into value-added products. Carbonization/activation (2 h/2 h) at 700 °C in a vertical furnace (20 K/min), to produce biochar and activated carbon (AC) from bamboo, orange, and paulownia residue, was carried out in a laboratory facility with physical activation by CO₂ and steam. The characterization of the carbonaceous material obtained was based on the determination of the N₂ adsorption-desorption isotherms at 77 K, the specific surface area with the BET procedure, and its internal structure by means of SEM images. The BET surface area values obtained as a function of the CO₂/steam agent used were 911/1182 m²/g, 248/388 m²/g, and 800/1166 m²/g for bamboo, orange, and paulownia, respectively. The range of variation of porosity in paulownia residue generated after steam activation was 485-1166 m²/g, varying depending on the degree of maturity of the biomass used. Research has shown that both the type of activation agent used to produce AC and the degree of plant maturation of the precursor residue affect the quality and characteristics of the final product.

Pseudomonas alcaliphila NEWG-2 as biosorbent agent for methylene blue dye: optimization, equilibrium isotherms, and kinetic processes

In comparison to physicochemical and chemical methods, microbial dye biosorption is regarded as an eco-effective and economically viable alternative and is a widely applied method due to its high efficiency and compatibility with the environment. Therefore, the idea of this study is to clarify to what extent the viable cells and the dry biomass of Pseudomonas alcaliphila NEWG-2 can improve the biosorption of methylene blue (MB) from a synthetic wastewater sample. The array of Taguchi paradigm has been conducted to ascertain five variables affecting the biosorption of MB by broth forms of P. alcaliphila NEWG. The data of MB biosorption were familiar to the predicted ones, indicating the precision of the Taguchi model's prediction. The maximum biosorption of MB (87.14%) was achieved at pH 8, after 60 h, in a medium containing 15 mg/ml MB, 2.5% glucose, and 2% peptone, with sorting the highest signal-to-noise ratio (38.80). FTIR spectra detected various functional groups (primary alcohol, α, β-unsaturated ester, symmetric NH2 bending, and strong C-O stretching) on the bacterial cell wall that participated in the biosorption of MB. Furthermore, the spectacular MB biosorption ability was validated by equilibrium isotherms and kinetic studies (the dry biomass form), which were derived from the Langmuir model (qmax = 68.827 mg/g). The equilibrium time was achieved in about 60 min, with 70.5% of MB removal. The biosorption kinetic profile might be adequately represented by pseudo-second order and Elovich models. The changes in the bacterial cells before and after the biosorption of MB were characterized using a scanning electron microscope. As realized from the aforementioned data, the bacterium is a talented, effective, eco-friendly, and low-cost bio-sorbent for the decolorization and remedy of an industrial effluent containing MB from an aqueous environment. The current outcomes in the biosorption of MB molecules promote the use of the bacterial strain as viable cells and/or dry biomass in ecosystem restoration, environmental cleanup, and bioremediation studies.

Preparation and characterization of activated carbon from agricultural wastes and their ability to remove chlorpyrifos from water

Chlorpyrifos is an organophosphate insecticide linked to neurological dysfunctions, endocrine disturbance, cardiovascular illness, genotoxicity, histopathological abnormalities, immunotoxicity, and oxidative stress. Therefore, the aim of this study was to prepare activated carbon from agricultural waste to adsorb and remove chlorpyrifos from aqueous solutions, as well as to study the physicochemical characteristics of the prepared activated carbon.Activated carbon was prepared from agricultural waste (banana peels, orange peels, pomegranate peels and date stones). The activated carbon prepared showed an exterior surface that was irregular and full of cavities with Brunauer-Emmett-Teller(BET) surface areas of 94.26, 111.75, 183.89, and 289.86 m²/g for activated carbon prepared from orange peels, date stone, pomegranate peels, and banana peels respectively. The Scanning Electron Microscope (SEM) image revealed that the activated carbon's exterior surface was irregular and full of various shapes and sizes of cavities.The Energy Dispersive X-Ray (EDX) indicated the existence of carbon, oxygen, silicon and potassium in banana peels-derived activated carbon, whereas carbon, oxygen, silicon and potassium, in addition to aluminium, were detected in the pomegranate peels-derived activated carbon. The Fourier-Transform Infrared Spectroscopy (FTIR) analysis of prepared activated carbon revealed several functional groups, including carboxylic acid, carbon dioxide, and aromatic compounds. Results also showed that the activated carbon significantly removed chlorpyrifos from water, recording 97.6%, 90.6%, 71.48%, and 52.00 % for activated carbon prepared from pomegranate peels, banana peels, date stones and orange peels, respectively. The study concluded that agricultural waste-derived activated carbon could be employed as an alternative pesticide adsorbent.

Adsorption and Kinetics Studies of Cr (VI) by Graphene Oxide and Reduced Graphene Oxide-Zinc Oxide Nanocomposite

In this work, graphene oxide (GO) and its reduced graphene oxide-zinc oxide nanocomposite (rGO-ZnO) was used for the removal of Cr (VI) from aqueous medium. By employing a variety of characterization techniques, morphological and structural properties of the adsorbents were determined. The adsorption study was done by varying concentration, temperature, pH, time, and amount of adsorbent. The results obtained confirmed that rGO-ZnO is a more economical and promising adsorbent for removing Cr (VI) as compared to GO. Kinetic study was also performed, which suggested that sorption of Cr (VI) follows the pseudo-first-order model. For equilibrium study, non-linear Langmuir was found a better fitted model than its linearized form. The maximum adsorption capacity calculated for GO and rGO-ZnO nanocomposite were 19.49 mg/g and 25.45 mg/g, respectively. Endothermic and spontaneous nature of adsorption was detected with positive values of ΔS (change in entropy), which reflects the structural changes happening at the liquid/solid interface.

Removal of Safranin-T and Toluidine from Water through Gum Arabic/Acrylamide Hydrogel

Hydrogels as “smart sorbents” for wastewater treatment have attracted much attention due to their facile fabrication, rapid regeneration, environment friendly nature, and strong interaction with pollutants. In this study, gum arabic/acrylamide (GA/AM) hydrogel was developed via the free radical polymerization method by employing acrylamide (AM) (monomer), gum arabic (GA) (grafting backbone), N,N-methylenebisacrylamide (MBA) (chemical crosslinker), and tetramethylethylenediamine (TEMED) (accelerator). The fabricated adsorbent was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and surface area analyzer. The adsorption properties of the subject hydrogel were explored against cationic safranin and toluidine dyes in aqueous media. The point of zero charge (PZC) for the GA/AM sorbent was found to be $\text{p}{\text{H}}_{\text{PZC}}=7.1$ whereas maximum sorption occurred at pH 11. Different kinetic and isotherm models were applied to evaluate the adsorption mechanism and estimate values of different adsorption parameters. The adsorption isotherm and kinetics were better explained by the Langmuir isotherm and pseudo-second-order kinetic model whereas the adsorption thermodynamics depicted the endothermic, spontaneous, and favorable nature of the process. The adsorbent was regenerated with acetone and reused for the selected dyes for many cycles. After the 5th cycle, the hydrogel retained safranin/toluidine removal $\text{capacity}\ge 60\%$ which pointed toward the reusability of the prepared adsorbent for cycles without appreciable reduction in its adsorption capacity. Hence, the GA/AM sorbent can be applied as an alternative of activated carbon to treat dye-contaminated waters.

Editorial to Efficient Catalytic and Microbial Treatment of Water Pollutants

Several industries produce products and release waste compounds that can be very carcinogenic, and furthermore, can cause trouble for water organisms, such as algae and plants which rely on photosynthesis [...]

Nitrate removal under low carbon to nitrogen ratio by modified corn straw bioreactor: Optimization and possible mechanism

ABSTRACTThe removal of nitrate (NO₃^--N) from water bodies under the conditions of poor nutrition and low carbon to nitrogen (C/N) ratio is a widespread problem. In this study, modified corn stalk (CS) was used to immobilize Burkholderia sp. CF6 with cellulose-degrading and denitrifying abilities. The optimal operating parameters of the bioreactor were explored. The results showed that under the hydraulic retention time (HRT) of 3 h and the C/N ratio of 2.0, the maximum nitrate removal efficiency was 96.75%. In addition, the organic substances in the bioreactor under different C/N ratios and HRT were analyzed by three-dimensional fluorescence excitation-emission mass spectrometry (3D-EEM), and it was found that the microorganisms have high metabolic activity. Scanning electron microscope (SEM) showed that the new material has excellent immobilization effects. Fourier transform infrared spectrometer (FTIR) showed that it has potential as a solid carbon source. Through high-throughput sequencing analysis, Burkholderia sp. CF6 was observed as the main bacteria present in the bioreactor. These research results showed that the use of waste corn stalks waste provides a theoretical basis for the advanced treatment of low C/N ratio wastewater.

The Synthesis of Magnetic Nitrogen-Doped Graphene Oxide Nanocomposite for the Removal of Reactive Orange 12 Dye

Herein, we report the nanofabrication of magnetic calcium ferrite (CaFe2O4) with nitrogen-doped graphene oxide (N-GO) via facile ultrasonication method to produce CaFe2O4/N-GO nanocomposite for the potential removal of reactive orange 12 (RO12) dye from aqueous solution. The successful construction of the nanocomposite was confirmed using different characterization techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The magnetic properties were studied using vibrating sample magnetometer (VSM) indicating ferromagnetic behavior of the synthesized materials that facilitate their separation using an external magnetic field after adsorption treatment. The addition of N-GO to CaFe2O4 nanoparticles enhanced the BET surface area from 24 to 52.93 m2/g as resulted from the N2 adsorption-desorption isotherm. The adsorption of the synthesized nanomaterials is controlled by several parameters (initial concentration of dye, contact time, adsorbent dosage, and pH), and the RO12 dye removal on the surface of CaFe2O4 nanoparticles and CaFe2O4/N-GO nanocomposite was reached through the chemisorption process as indicated from the kinetic study. The adsorption isotherm study indicated that the adsorption process of RO12 dye was best described through the Langmuir isotherm approving the monolayer adsorption. According to the Langmuir model, the maximum adsorption capacity for RO12 was 250 and 333.33 mg/g for CaFe2O4 nanoparticles and CaFe2O4/N-GO nanocomposite, respectively. The adsorption capacity offered by CaFe2O4/N-GO nanocomposite was higher than reported in the literature for adsorbent materials. Additionally, the regeneration study indicated that CaFe2O4/N-GO nanocomposite is reusable and cost-effective adsorbent. Therefore, the nanofabricated CaFe2O4/N-GO hybrid material is a promising adsorbent for water treatment.

Recovery of Waste Polyurethane from E-Waste. Part II. Investigation of the Adsorption Potential for Wastewater Treatment

This study explored the performances of waste polyurethane foam (PUF) derived from the shredding of end-of-life refrigerators as an adsorbent for wastewater treatment. The waste PUF underwent a basic pre-treatment (e.g., sieving and washing) prior the adsorption tests. Three target pollutants were considered: methylene blue, phenol, and mercury. Adsorption batch tests were performed putting in contact waste PUF with aqueous solutions of the three pollutants at a solid/liquid ratio equal to 25 g/L. A commercial activated carbon (AC) was considered for comparison. The contact time necessary to reach the adsorption equilibrium was in the range of 60-140 min for waste PUF, while AC needed about 30 min. The results of the adsorption tests showed a better fit of the Freundlich isotherm model (R2 = 0.93 for all pollutants) compared to the Langmuir model. The adsorption capacity of waste PUF was limited for methylene blue and mercury (Kf = 0.02), and much lower for phenol (Kf = 0.001). The removal efficiency achieved by waste PUF was lower (phenol 12% and methylene blue and mercury 37-38%) compared to AC (64-99%). The preliminary results obtained in this study can support the application of additional pre-treatments aimed to overcome the adsorption limits of the waste PUF, and it could be applied for "rough-cut" wastewater treatment.

Biodegradation of Brown 706 Dye by Bacterial Strain Pseudomonas aeruginosa

Dyes are the most challenging pollutants for the aquatic environment that are not only toxic, but also interfering photosynthesis as light penetration into deep water is changed. A number of methods are used for the water reclamation, however, among them biological methods are preferably used due to their compatibility with nature. In the present research, 15 different bacterial strains were used to decolorize Brown 706 dye. Among the bacterial strains, Pseudomonas aeruginosa showed maximum decolorization activity; hence in the subsequent experiments Pseudomonas aeruginosa was used. First the decolorization activities were carried out under different physicochemical conditions to obtain the optimum decolorization benefits of the selected microorganism. The optimum conditions established were 37°C, pH of 7 and operation cycle time 72 h. In the subsequent experiment all optimum conditions were combined in a single experiment where 73.91% of decolorization efficiency was achieved. For the evaluation of metabolites formed after decolorization/degradation the aliquots containing bacteria were homogenized, filtered and then subjected to extraction. The extracted metabolites were then subjected to the silica gel column isolation. UV–Vis, FTIR, and NMR techniques were used to elucidate structures of the metabolites. Out of the collected metabolites only P-xylene was identified, which has been formed by cleavage of azo linkage by azo reductase enzyme of bacteria following the deamination and methylation of nitro substituted benzene ring.

Adsorption Kinetics and Isotherm Study of Basic Red 5 on Synthesized Silica Monolith Particles

The Silica monolith particles (SMP) were prepared from Tetra-Methyl-Ortho-Silicate (TMOS) and characterized by Fourier transforms infrared (FTIR), Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and surface area analyzer. FTIR analysis showed the Si−O stretching confirming SMP formation. SEM analysis provided information about the mean diameter of SMP (1−5 µm). EDX confirmed the presence of silicon and oxygen in the SMP. Moreover, the calculated surface area for SMP was found to be around 367 m2/g, whereas BJH pore size distributed particles were 87.15 along with the total pore volume and pore radius of 0.073 cm3/g and 16.627 Å, respectively. Besides, the removal efficiency was found to be about 96%. Various kinetic equations were used to calculate the adsorption parameters. Overall, the results show that the most appropriate model for the kinetics data was the pseudo-second order kinetics model while the mechanism of adsorption was best explained by the Langmuir isotherm. The highest removal of Basic Red 5 dye after 120 min at 298 K was 576 mg/g. Moreover, the thermodynamics parameters (Enthalpy, Gibb’s energy, and Entropy) were also estimated. The ΔH° (0.995 kJ/mol) value depicted the endothermic nature of the process. The non-spontaneous aspect of the process was evident from the ΔG° values which were 60.431, 328.93, and 339.5 kJ/mol at 293, 303, and 313 K, respectively. From the high removal efficiency value, it can be concluded that the prepared adsorbent can be a potential adsorbent in the reclamation of dyes from wastewater.

Activated Ailanthus altissima Sawdust as Adsorbent for Removal of Acid Yellow 29 from Wastewater: Kinetics Approach

In this study, Ailanthus altissima sawdust was chemically activated and characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR), Energy Dispersive X rays (EDX), and surface area analyzer. The sawdust was used as an adsorbent for the removal of azo dye; Acid Yellow 29 (AY 29) from wastewater. Different kinetic and equilibrium models were used to calculate the adsorption parameters. Among the applied models, the more suitable model was Freundlich with maximum adsorption capacities of 9.464, 12.798, and 11.46 mg/g at 20 °C, 30 °C, and 40 °C respectively while R2 values close to 1. Moreover, the kinetic data was best fitted in pseudo second order kinetic model with high R2 values approaching to 1. Furthermore, adsorption thermodynamics parameters such as free energy, enthalpy, and entropy were calculated and the adsorption process was found to be exothermic with a value of ∆H° = −9.981 KJ mol−1, spontaneous that was concluded from ΔG° values which were negative (−0.275, −3.422, and −6.171 KJ mol−1 at 20, 30, and 40 °C respectively). A positive entropy change ∆S° with a value of 0.0363 KJ mol−1 indicated the increase disorder during adsorption process. It was concluded that the activated sawdust could be used as a suitable adsorbent for the removal of waste material, especially dyes from polluted waters.

Use of Aloe vera as an Organic Coagulant for Improving Drinking Water Quality

The coagulation–flocculation–sedimentation process is widely used for removal of suspended solids and water turbidity reduction. The most common coagulants used to conduct this process are aluminum sulfate and ferric sulfate. In this paper, the use of Aloe vera as a natural-based coagulant for drinking water treatment was tested. The bio-coagulant was used in two different forms: powder as well as liquid; the latter was extracted with distilled water used as a solvent. The obtained results showed that the use of the natural coagulant (Aloe vera) in both powder (AV-Powder) and liquid (AV-H2O) forms reduced the water turbidity at natural pH by 28.23% and 87.84%, respectively. Moreover, it was found that the use of the two previous forms of bio-coagulant for drinking water treatment had no significant influence on the following three parameters: pH, alkalinity, and hardness. The study of the effect of pH on the process performance using Aloe vera as a bio-coagulant demonstrated that the maximum turbidity removal efficiency accounted for 53.53% and 88.23% using AV-Powder and AV-H2O, respectively, at optimal pH 6.

Diversity of Synthetic Dyes from Textile Industries, Discharge Impacts and Treatment Methods

Natural dyes have been used from ancient times for multiple purposes, most importantly in the field of textile dying. The increasing demand and excessive costs of natural dye extraction engendered the discovery of synthetic dyes from petrochemical compounds. Nowadays, they are dominating the textile market, with nearly 8 × 105 tons produced per year due to their wide range of color pigments and consistent coloration. Textile industries consume huge amounts of water in the dyeing processes, making it hard to treat the enormous quantities of this hazardous wastewater. Thus, they have harmful impacts when discharged in non-treated or partially treated forms in the environment (air, soil, plants and water), causing several human diseases. In the present work we focused on synthetic dyes. We started by studying their classification which depended on the nature of the manufactured fiber (cellulose, protein and synthetic fiber dyes). Then, we mentioned the characteristics of synthetic dyes, however, we focused more on their negative impacts on the ecosystem (soil, plants, water and air) and on humans. Lastly, we discussed the applied physical, chemical and biological strategies solely or in combination for textile dye wastewater treatments. Additionally, we described the newly established nanotechnology which achieves complete discharge decontamination.

Effective Poly (Cyclotriphosphazene-Co-4,4'-Sulfonyldiphenol)@rGO Sheets for Tetracycline Adsorption: Fabrication, Characterization, Adsorption Kinetics and Thermodynamics

The development of excellent drug adsorbents and clarifying the interaction mechanisms between adsorbents and adsorbates are greatly desired for a clean environment. Herein, we report that a reduced graphene oxide modified sheeted polyphosphazene (rGO/poly (cyclotriphosphazene-co-4,4'-sulfonyldiphenol)) defined as PZS on rGO was used to remove the tetracycline (TC) drug from an aqueous solution. Compared to PZS microspheres, the adsorption capacity of sheeted PZS@rGO exhibited a high adsorption capacity of 496 mg/g. The adsorption equilibrium data well obeyed the Langmuir isotherm model, and the kinetics isotherm was fitted to the pseudo-second-order model. Thermodynamic analysis showed that the adsorption of TC was an exothermic, spontaneous process. Furthermore, we highlighted the importance of the surface modification of PZS by the introduction of rGO, which tremendously increased the surface area necessary for high adsorption. Along with high surface area, electrostatic attractions, H-bonding, π-π stacking and Lewis acid-base interactions were involved in the high adsorption capacity of PZS@rGO. Furthermore, we also proposed the mechanism of TC adsorption via PZS@rGO.