Real Wastewater Systems Research Articles

Inducing oxygen vacancies in ZnO/Co3O4 via g-C3N4 carrier for enhanced universality and stability in TC degradation

The universality and stability are significant for efficient environmental catalysts. Herein, a series of g-C3N4 supported ZnO/Co3O4 nanocomposites (ZCO-CN) were constructed through the one-pot pyrolysis method. The constructed ZCO-CN composites showed superior properties in peroxymonosulfate (PMS) activation to degrade tetracycline (TC) with remarkable universality and stability. It has been able to accommodate common anions and cations and a wide pH range (3−11) in the real wastewater system with a removal rate of 91% within 5 min. After 5 cycles, the degradation rate can still be maintained at 83.8%. Moreover, ZCO-CN still displayed outstanding catalytic performance for methyl orange and oxytetracycline. The singlet oxygen (1O2) and superoxide radicals (∙O2-) during the TC degradation process are confirmed through quenching experiments and electron paramagnetic resonance (EPR) analysis. The abundant N in the support of g-C3N4 can form interactions with ZnO/Co3O4 (ZCO) facilitating the formation of oxygen vacancies, which promotes the formation of 1O2, inhibits the leaching of metal ions and significantly enhances the stability of the catalyst. This work proposes an immobilized ZnO/Co3O4/g-C3N4 with enhanced catalytic performance, high universality, and stability for PMS activated toward pollution removal.

SnS2 modified carbonate-intercalated Ni-Zn-Fe trimetallic LDH as a novel photocatalyst for persulfate activation: Influence of operational parameters, co-existing ions and organic compounds

Herein, novel SnS2/CO32–@ Ni-Fe-Zn LDH (SCL) QDs were fabricated by growing carbonate-intercalated Ni-Fe-Zn LDH over SnS2 nanoparticles via a facile co-precipitation technique to activate persulphate (PS) under visible light irradiation. Ofloxacin (OFL) was chosen as an emerging organic pollutant to appraise the photocatalytic activity of the SCL + PS system under visible light irradiation. The effect of various process parameters affecting PS activation was assessed, and the mechanism of the degradation of OFL via PS activation is presented. The study of the synergistic effect of SCL for PS activation versus H2O2 activation showed that it is a better PS activator compared to the H2O2 activator. About 93.11 ± 1.46 % of 20 ppm OFL with a catalyst dosage of 0.4 g/L and PS concentration of 6 mM was degraded within 100 min at neutral pH. The effect of inorganic cations, anions, dissolved organic matter, and water matrices was also investigated to examine the applicability of the SCL + PS system under a real wastewater system. Furthermore, the reusability tests suggested that the prepared photocatalyst was highly stable and reusable for up to five consecutive cycles. Moreover, the as-prepared SCL QDs also showed significant degradation of other emerging pollutants with a degradation efficiency of>80 %. The present research highlighted the significance of SCL for PS activation under visible light for the photodegradation of emerging pollutants and wastewater treatment.

Trials on ciprofloxacin removal from wastewater using a photocatalytic membrane reactor

Trials on ciprofloxacin removal from real aqueous systems were performed using a photocatalytic membrane reactor with catalyst in suspension. Four sets of four treatment cycles were carried out and experimental results were processed from the statistical point of view in order to assess results reproducibility. Global ciprofloxacin removal efficiencies of more than 99.85% were obtained for all treatment cycles. Coupling of photocatalytic degradation with membrane process allowed catalyst separation and reuse within further treatment cycles. Statistical analyse of experimental data recommends the use of photocatalytic membrane reactors as a feasible option for the advanced removal of pharmaceutical products like ciprofloxacin from real wastewater systems.

Competitive adsorption of anionic and cationic molecules on three activated carbons derived from agroindustrial waste

This study examined the feasibility of sugarcane bagasse (sb), spent coffee-grounds (sg), and orange peel (op) activated carbons for the removal of methyl orange (MO) and methylene blue (MB). For such purpose, individual dye solutions and binary mixtures under different pH and initial concentrations were used. The study was complemented with Density Functional Theory (DFT) calculations to assess the carbon surface preference towards a specific molecule. The DFT method, using molecular descriptors, showed a potential application for predicting the order by which the carbons sorb a given set of contaminants. For the three carbon materials studied, the mono-dye experiments adsorption capacities ranged from 60 to 140 mg/g for MB and from 146 to 65 mg/g for MO at pH values of 5, 7 and 9. While the best methylene blue adsorbent was the sugarcane bagasse carbon, the orange peel carbon showed the best methyl orange adsorption capacity. Interestingly, the spent coffee-ground carbon exhibited a balanced behavior when both molecules were added separately. When the dyes were added as a mixture, the three carbons adsorbed methylene blue preferentially over methyl orange. While sb adsorbed up to 75 mg/g of MB and 10 mg/g of MO, op adsorbed 60 mg/g of MB and up to 25 mg/g of MO. The trend displayed in mono-dye systems was kept in binary systems. This is important since real wastewater systems contain mixtures with two or more pollutants. In the case of the binary mixtures, the three activated carbons can adsorb both type of dyes at concentrations up to 300 mg/L, the pH did not affect the MB adsorption, whereas MO uptake was greatly affected at pH > 7. Thus, it is important to study versatile materials obtained from organic wastes capable of removing more than one species from wastewater.

Surface modification of thin film composite forward osmosis membrane using tris(2-aminoethyl)amine for enhanced ammonium recovery

In this study, we aimed to develop a forward osmosis (FO) thin film composite (TFC) membrane which could retain NH4+ from wastewater. The conventional TFC membrane has a microporous polymer support and a selective layer for salt rejection; however, the polyamide selective layer is known to not be able to reject NH4+. Our strategy was to develop tris(2-aminoethyl)amine (TAEA)-modified TFC membranes via secondary interfacial polymerization, and the modification factors were optimized. The NH4+ rejection of the optimized membrane significantly increased from 64.9 % (pristine TFC) to 94.7 %. TAEA modification resulted in a smoother surface and thinner polyamide selective layers. The mechanism of NH4+ rejection during FO operation was investigated and was found to be influenced by membrane surface carboxylic group density and the polyamide crosslinking, cation exchange between the draw and feed solutions, and size sieving. In conclusion, the TAEA-modified membrane showed high selectivity against NH4+ and applicability for NH4+ recovery. In the future, the TAEA-modified membrane may be applied for NH4+ enrichment and recovery from real wastewater systems.

Zinc Oxide Nanoparticles and Their Application in Adsorption of Toxic Dye from Aqueous Solution.

Dye waste is one of the most serious types of pollution in natural water bodies, since its presence can be easily detected by the naked eye, and it is not easily biodegradable. In this study, zinc oxide nanoparticles (ZnO-NPs) were generated using a chemical reduction approach involving the zinc nitrate procedure. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and UV-vis techniques were used to analyse the surface of ZnO-NPs. The results indicate the creation of ZnO-NPs with a surface area of 95.83 m2 g−1 and a pore volume of 0.058 cm3 g−1, as well as an average pore size of 1.22 nm. In addition, the ZnO-NPs were used as an adsorbent for the removal of Ismate violet 2R (IV2R) dye from aqueous solutions under various conditions (dye concentration, pH, contact time, temperature, and adsorbent dosage) using a batch adsorption technique. Furthermore, FTIR and SEM examinations performed before and after the adsorption process indicated that the surface functionalisation and shape of the ZnO-NP nanocomposites changed significantly. A batch adsorption analysis was used to examine the extent to which operating parameters, the equilibrium isotherm, adsorption kinetics, and thermodynamics affected the results. The results of the batch technique revealed that the best results were obtained in the treatment with 0.04 g of ZnO-NP nanoparticles at 30 °C and pH 2 with an initial dye concentration of 10 mg L−1, which removed 91.5% and 65.6% of dye from synthetic and textile industry effluents, respectively. Additionally, six adsorption isotherm models were investigated by mathematical modelling and were validated for the adsorption process, and error function equations were applied to the isotherm model results in order to find the best-fit isotherm model. Likewise, the pseudo-second-order kinetic model fit well. A thermodynamic study revealed that IV2R adsorption on ZnO-NPs is a spontaneous, endothermic, and feasible sorption process. Finally, the synthesised nanocomposites prove to be excellent candidates for IV2R removal from water and real wastewater systems.

Effective removal of remazol brillinat orange 3R using a biochar derived from Ulva reticulata

ABSTRACT Marine seaweed is considered as one of the efficient tools for the mitigation of carbon dioxide and it is naturally overgrown in India. Biochar produced from seaweeds will remediate the toxic pollutants present in the soil and wastewater. The current investigation examined the potential of biochar synthesized from Ulva reticulata for the decolorization of Remazol Brilliant Orange 3 R (RBO3R). An up-flow-packed bed column is designed to check the feasibility of the effluent treatment in a real wastewater system. The partition coefficient was calculated to elucidate the optimal initial RBO3R concentration that has the highest affinity toward the biochar and the column operating parameters namely sorbent bed depth, flowrate and the initial RBO3R concentration were also studied. To validate the experimental data mathematical models namely the modified dose-response model (MDR) and Yoon Nelson model (YN) were developed. The results concluded that the removal efficiency of 69.08% and sorption capacity of 0.1046 mmol/g was obtained. The biochar potential has been assessed by conducting three sorptions and an elution cycle continuously using 0.01 M sodium hydroxide as the elutant.

Surfactant-modified three-dimensional layered double hydroxide for the removal of methyl orange and rhodamine B: Extended investigations in binary dye systems

Dyes pollution have raised great attention due to its fatal harm on aquatic ecosystem and human health. Generally, multiple dyes (anionic dyes, cationic dyes) present in real wastewater systems. In this work, methyl orange (MO) as anionic dye and rhodamine B (RhB) as cationic dye were chosen as typical dyes to investigate the removal behavior with surfactant-modified three-dimensional MgAl layered double hydroxide (S3D-LDH) via macroscopic and microscopic analyses. Adsorption isotherms revealed that the maximum adsorption capacity of MO and RhB could reach 380.2 and 49.6 ​mg·g−1, respectively. The removal process between S3D-LDH and ionic dyes was identified to be a chemical reaction via adsorption kinetics. XRD and MIR demonstrated a decrease of d-spacing value and a red shift of the stretching vibration of lattice water and hydroxyl group in the MO removal and increased d-spacing and a blue shift of water with hydroxyl group in the RhB removal. X-ray photoelectron spectroscopy (XPS) revealed that the RSO3 peak emerged after MO adsorption and the negative bond shift of unbound sulfur of S 2p after RhB adsorption. All investigations revealed that MO adsorbed by S3D-LDH via anion exchange and hydrogen bonding whereas surface adsorption was deemed as the primary pathway for RhB. Furthermore, the MO and RhB adsorption capacity by S3D-LDH was both enhanced in binary component systems. S3D-LDH was demonstrated as a potential broad-spectrum adsorbent for the treatment of dyes wastewater.

A treatment of wastewater containing basic dyes by the use of new strain Streptomyces microflavus CKS6

This study has investigated the biodegradable potential of the Streptomyces microflavus CKS6 growing microbial cells for the colored waste water treatment. The Crystal violet and Safranin T basic dyes have been employed as a model compounds for decolorization evaluation by exploring the correlation with the other rate-dependent environmental parameters. Through the measuring of color reduction by UV–Vis spectroscopic monitoring analysis, the results revealed well operational properties of Streptomyces microflavus CKS6 for the successful refinement of dyes contaminate water solutions. Optimized process parameters were found to be apparently mild, involving the use of the reaction temperature of 27–30 °C and pH 6–7. With the lower dye concentrations, the decolorization efficiency was found to be more effective and rapid, wherein the 1 mg/L of Crystal violet was removed within the 2.5 h of the treatment time, while the solution with the same content of the Safranin T dye required 30 h. A possible mechanism for the working medium decolorization was accomplished in two consecutive steps, by the primarily dye adsorption onto the bacterial cells surface, followed to biodegradation by the active microbial enzymatic system, wherein the lignin peroxidase acts a notable role. The phytotoxicity analysis of the degradation products revealed less toxicity to the plants, compared to parental chemicals. In addition, the adaptation of individual dye optimized parameters was effectively implemented in the real waste water system containing the mixture of these two dyes. The overall results may postulate that Streptomyces microflavus CKS6 may be promising applicants for dye contaminated water treatment.

Applicability of agricultural waste and by-products for adsorptive removal of heavy metals from wastewater

This critical review discusses the potential use of agricultural waste based biosorbents (AWBs) for sequestering heavy metals in terms of their adsorption capacities, binding mechanisms, operating factors and pretreatment methods. The literature survey indicates that AWBs have shown equal or even greater adsorption capacities compared to conventional adsorbents. Thanks to modern molecular biotechnologies, the roles of functional groups in biosorption process are better understood. Of process factors, pH appears to be the most influential. In most cases, chemical pretreatments bring about an obvious improvement in metal uptake capacity. However, there are still several gaps, which require further investigation, such as (i) searching for novel, multi-function AWBs, (ii) developing cost-effective modification methods and (iii) assessing AWBs under multi-metal and real wastewater systems. Once these challenges are settled, the replacement of traditional adsorbents by AWBs in decontaminating heavy metals from wastewater can be expected in the future.

Concentrating versus non-concentrating reactors for solar water detoxification

Solar detoxification of a pure model compound (dichloroacetic acid) as well as of real waste waters was studied. Different types of reactors, light concentrating and non-concentrating were used and their advantages and disadvantages were compared and discussed. For this purpose a dimensionless number, the photoreactor number was introduced. Also the influence of different electron acceptors (hydrogen peroxide and oxygen) on the degradation process was studied, both in the model system and the real waste water system.