Selective recovery of salt from coal gasification brine by nanofiltration membranes

Recovery of Biologically Treated Textile Wastewater by Ozonation and Subsequent Bipolar Membrane Electrodialysis Process

The Bipolar Membrane Electrodialysis process (BPMED) can produce valuable chemicals such as acid (HCl, H₂SO₄, etc.) and base (NaOH) from saline and brackish waters under the influence of an electrical field. In this study, BPMED was used to recover wastewater and salt in biologically treated textile wastewater (BTTWW). BPMED process, with and without pre-treatment (softening and ozonation), was evaluated under different operational conditions. Water quality parameters (color, remaining total organic carbon, hardness, etc.) in the acid, base and filtrated effluents of the BPMED process were evaluated for acid, base, and wastewater reuse purposes. Ozone oxidation decreased 90% of color and 37% of chemical oxygen demand (COD) in BTTWW. As a result, dye fouling on the anion exchange membrane of the BPMED process was reduced. Subsequently, over 90% desalination efficiency was achieved in a shorter period. Generated acid, base, and effluent wastewater of the BPMED process were found to be reusable in wet textile processes. Results indicated that pre-ozonation and subsequent BPMED membrane systems might be a promising solution in converging to a zero discharge approach in the textile industry.

Review on characteristics of biomaterial and nanomaterials based polymeric nanocomposite membranes for seawater treatment application

Membrane technology, especially nanofiltration (NF) has great attention to provide an imperative solution for water issues. The membrane is considered to be the heart in the separation plant. Understanding the membrane characteristics could allow predicting and optimizing the membrane performance namely flux, rejection and reduced fouling. The membrane development using biomaterials and nanomaterials provides a remarkable opportunity in the water application. This review focuses on the membrane characteristics of biomaterials and nanomaterials based nanofiltration. In this review, recent researches based on biomaterials and nanomaterials loaded membrane for salt rejection have been analyzed. Membrane fouling depends on the membrane characteristics and this review defined fouling as a ubiquitous bottleneck challenge that hampers the NF blooming applications. Fouling mitigation strategies via membrane modification using biomaterial (chitosan, curcumin and vanillin) and various other nanomaterials are critically reviewed. This review also highlights the membrane cleaning and focuses on concentrates disposal methods with zero liquid discharge system for resource recovery. Finally, the conclusion and future prospects of membrane technology are discussed. From this current review, it is apparent that the biomaterial and various other nanomaterials acquire exclusive properties that facilitate membrane advancement with improved capability for water treatment. Regardless of membrane material developments, still exist considerable difficulties in membrane commercialization. Thus, additional studies related to this field are needed to produce membranes with better performance for large‒scale applications.

Application of nanofiltration and reverse osmosis for treatment and reuse of laundry wastewater

The aim of this study was to investigate the treatment and reuse of laundry wastewater with couple of nanofiltration (NF) and reverse osmosis (RO). In the NF process, optimal values of pH, temperature, transmembrane pressure (TMP) and cross-flow rate were determined using the Taguchi L₁₆ (4⁴) experimental design method. The smaller-the-better signal-to-noise (S/N) ratio was used to analyze the results of experiments. Flux decline caused by fouling was selected as response parameter. A pH of 8.5, temperature of 30 °C, TMP of 12 bar and cross-flow rate of 2 L/min were determined as optimum operating conditions in the NF process. According to analysis of variance (ANOVA), pH was the most effective factor while TMP and cross-flow rate had low effects on the fouling. Membrane fouling was also evaluated with scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), zeta potential and optical profilometer measurements. In the RO process, the quality of NF permeate obtained from optimum operating conditions was improved by an RO membrane. Although a NF membrane was not effective in reducing chemical oxygen demand (COD), Orto-P and NH₄ ⁺-N, these parameters were almost removed in the NF + RO system. These results showed that, the Taguchi method was successfully applied to determine the optimum operating conditions for the treatment of laundry wastewater with an NF process. Water treated with integrated membrane processes (NF + RO) is sufficient for use as laundry washing water.

Enhanced nitrogen removal of coal pyrolysis wastewater with low COD to nitrogen ratio by partial nitrification-denitrification bioprocess assisted with polycaprolactone

The purpose of this study is to investigate the enhancement of polycaprolactone (PCL) on total nitrogen (TN) removal of coal pyrolysis wastewater (CPW) with low COD to nitrogen ratio by partial nitrification-denitrification bioprocess (PNDB) in one single reactor. With the innovative combination of PCL and PNDB, the TN removal efficiency in the experimental reactor (signed as R1) was 10.21% higher than control reactor (R2). Nitrite accumulation percentage (NAP) in R1 was 82.02%, which was 17.49% higher than R2 at the dissolved oxygen (DO) concentration of 0.9-1.5 mg/L, for the reason that the extra DO was consumed by PCL biodegradation at the aerobic period. Gel permeation chromatography (GPC) results demonstrated that organics with the molecular weight of 185 Da, which could serve as additional carbon sources for denitrifiers, were generated during the PCL hydrolysis process at the anoxic period. PCL was hydrolyzed by extracellular enzymes with the break of the ester bond which was confirmed by FT-IR spectrometer. Microbial community analysis revealed that Ferruginibacter was the dominant hydrolysis bacteria in R1. Nitrosomonas were the main ammonium-oxidizing bacteria (AOB) and Hyphomicrobium were the denitrifiers in this study.

Selective adsorption and bioavailability relevance of the cyclic organics in anaerobic pretreated coal pyrolysis wastewater by lignite activated coke

This study originally investigated the selective adsorption of cyclic organics in APCPW by LAC, corresponding to the change of the bioavailability. As a product from low rank coal, LAC showed more oxygen (O)-containing groups and mesoporous structure than PAC. Adsorption mechanisms were analyzed by equilibrium isotherms and kinetics models combined with physicochemical properties of adsorbent and adsorbates. The results indicated that selectivity of LAC was dominated by chemical interaction and its mesoporous, and was enhanced by hydrophobicity of adsorbates. In addition, PAC and LAC were applied for the treatment of APCPW. Compared with PAC, LAC adsorption exhibited superior removal efficiency of Tph, TOC and TN at 85.90%, 91.15% and 51.64%, respectively. Furthermore, preferential adsorption of biotoxic and bioresistant cyclic organics by LAC was further proved by GC-MS analysis, resulting in increased bioavailability of APCPW. Specifically, LAC exerted sustained detoxication capacity until 86.50% reduction of TU by D. magna evaluation, and lowered toxicity rank (TU = 4.51, classIII) to T. pyriformis than that after PAC adsorption (TU > 10, ClassIV). Meanwhile, biodegradability was also improved by 9.17% after LAC adsorption. Lastly, LAC would exhibit great economic benefits as an alternative for PAC in subsequent process after anaerobic pretreatment.

Solution Blown Nylon 6 Nanofibrous Membrane as Scaffold for Nanofiltration

In this work, a nylon 6 nanofibrous membrane was prepared via solution blowing technology and followed hot-press as scaffold for nanofiltration. The structure and properties of the hot-pressed nylon 6 nanofibrous membrane (HNM) were studied the effect of hot-pressing parameters and areal densities. Then an ultra-thin polyamide (PA) active layer was prepared by interfacial polymerization on HNM. The effects of nanofibrous scaffolds on the surface properties of ultra-thin nanofiltration membranes and their filtration performance were studied. Results showed that the nylon 6 nanofibers prepared at a concentration of 15 wt % had a good morphology and diameter distribution and the nanofibers were stacked more tightly and significantly reduced in diameter after hot pressing at 180 °C under the pressure of 15 MPa for 10 s. When the porous scaffold was prepared, HNM with an areal density of 9.4 and 14.1 g/m² has a better apparent structure, a smaller pore size, a higher porosity and a greater strength. At the same time, different areal densities of HNM have an important influence on the preparation and properties of nanofiltration membranes. With the increase of areal density, the uniformity of HNM increased while their surface roughness and pore size decreased, which is beneficial to the establishment of PA barrier layer. With areal density of 9.4 and 14.1 g/m², the as-prepared nanofiltration membrane has a smoother surface and more outstanding filtration performance. The pure water flux is 13.1 L m⁻² h⁻¹ and the filtration efficiencies for NaCl and Na₂SO₄ are 81.3% and 85.1%, respectively.