Submerged microfiltration membrane coupled with alum coagulation/powdered activated carbon adsorption for complete decolorization of reactive dyes

Hydrothermal synthesis of Mg/Al-layered double hydroxide modified water hyacinth hydrochar for remediation of wastewater containing mordant brown dye

A high-performance dye adsorbent of Mg/Al-layered double hydroxide modified water hyacinth hydrochar (MgAl@WH) was synthesized by a simple hydrothermal method. The surface functional groups, elemental composition, crystalline structure, and surface morphology of the prepared (MgAl@WH) were determined using different analytical techniques. The characterization results revealed that the (MgAl@WH) hydrochar surface offered more active adsorption sites, facilitating the mordant brown (anionic dye) adsorption, leading to its superior performance with much higher uptake capability (311.0 mg g-1 at 298 K) than Mg/Al double hydroxide nanosheets (MgAl DLHs, 80.2 mg g-1 at 298 K) and dried water hyacinth (WH, 10.0 mg g-1 at 298 K). The adsorption behavior of MgAL@WH follows the pseudo second order kinetic model (R2 = 0.999) and Langmuir isotherm model (R2 = 0.999). Moreover, MgAl@WH bonded efficiently with mordant brown dye via hydrogen bonding and interlayer anion exchange with monolayer formation. Additionally, the recycling tests revealed that the MgAl@WH can be reused over 10 cycles without significant change in the removal efficiency. Based on the obtained findings, Mg/Al-layered double hydroxide modified water hyacinth hydrochar (MgAl@WH), for its economic and environmental benefits, has recently been used as an efficient adsorbent to remediate industrial wastewater containing anionic dyes.

Adsorption of azo dye by biomass and immobilized Yarrowia lipolytica; equilibrium, kinetic and thermodynamic studies

One of the major environmental problems we have today is dye pollution, primarily caused by the textile industry. This pollution has detrimental effects on aquatic life, soil fertility, and human health. Many microbial biosorbents have been documented in the literature for the removal of a wide range of azo dyes commonly employed in the textile industry. However, Yarrowia lipolytica NBRC1658 is firstly used as both free and immobilized sorbents for the removal of Reactive yellow 18 (RY18), acid red 18 (AR18) and basic blue 41 (BB41) in this study. The effect of experimental conditions such as pH, biosorbent quantity, dye concentration, contact time, and temperature on dye removal capacity are examined. The research findings demonstrate that the adsorption capacity is higher in biomass compared to immobilized cells. The highest adsorption capacities are observed at pH 2 for RY18 and AR18, while pH 9 is optimal for BB41. Increasing the adsorbent dosage and initial concentration significantly improves the adsorption capacity. The Langmuir model best describes the adsorption process, indicating that the dye attaches to the biosorbent in a single layer, with a uniform biosorbent surface. The removal of the dye occurs through a chemical process on the biosorbent surface, as evidenced by the pseudo-second-order kinetic model. According to thermodynamic analysis, higher temperatures promote greater adsorption of dyes. Our study shows the effectiveness of Yarrowia lipolyica NBRC1658 as a biosorbent in the removal of a wide range of industrial dyes.

Highlighting the adsorption mechanism of dyes onto activated carbon derived from sludge by theoretical physical analysis

An activated carbon (AC) deriving from sludge is used in this research for the adsorption of two water pollutants, namely Reactive Black 5 (RB5) and Green Alizarin (GA) dyes, at different temperatures. The adsorption capacities varied from 277.2 to 312.69 mg/g for GA and from 225.82 to 256.02 mg/g for RB5. Comparatively, this adsorbent presents good performances in removing these dyes from wastewater. The application of physical models to adsorption experiments is advantageous to provide new insights into the dyes' adsorption mechanism. A dedicated physical adsorption model suggests that RB5 and GA dyes are adsorbed in a monolayer. Moreover, the orientation of RB5 and GA dyes on AC resulted in an angled position, determining a multi-molecular process. In addition, both dyes are adsorbed by the occurrence of an aggregation process, forming a dimer. The impact of temperature can be also interpreted, allowing concluding that it plays a relevant role in removing these dyes. The calculation and interpretation of adsorption energies show that the dyes are removed via an endothermic process, and physical forces are involved.

Application of QSAR for investigation on coagulation mechanisms of textile wastewater

Coagulation is an effective preliminary treatment process for textile wastewater. In order to evaluate the effectiveness of the coagulation process, we performed quantitative structure activity relationship (QSAR) analyses with total organic carbon (TOC) removal rates (R_exp) as an index by three different coagulants (AlCl₃, FeCl₃, and MgCl₂). The experimental results showed that the average R_exp of the three coagulants was 39.12% ± 2.60%, 51.60% ± 2.88%, and 49.95% ± 3.17%. Subsequently, 42 molecular descriptors of dye molecules were calculated by quantitative calculation softwares Gaussian 09, Material Studio 7.0, and Multiwfn 3.7, and then QSAR models were constructed by a multiple linear regression (MLR) method for the three coagulation systems. The developed QSAR models demonstrated excellent stability, robustness, and predictability with values of R² = 0.7677, 0.8015, and 0.7035, Q²_INT = 0.6067, 0.7026, and 0.5898, Q²_EXT = 0.5505, 0.5076, and 0.5697, respectively. Based on the analysis of quantum parameters, the coagulation mechanism for AlCl₃, FeCl₃ is primarily electrostatic adsorption as well as hydrogen bonding, while MgCl₂ coagulates dyes mainly by electrostatic adsorption. This study provides an assessment of the removal rules and a feasible method for predicting dye removal rates in AlCl₃, FeCl₃, and MgCl₂ coagulation process.

Dendrimers: A Neuroprotective Lead in Alzheimer Disease: A Review on its Synthetic approach and Applications

Alzheimer disease is a neurodegenerative disease that is signified by cognitive decline, memory loss, and erratic behavior. Dendrimers are a type of polymer that has a well-defined structure, a high degree of molecular uniformity, and a low polydispersity which have shown to be effective intracellular drug carriers for bring down the in numerous cases. The data reported by the clinical trials and chemical bonds of dendrimers loading and biological properties that may be used in the bringing out the treatment of nano formulation for Alzheimer disease. Below-range dendrimers have an unlocked figure, but higher-range dendrimers have a more globular and dense structure so handling is difficult. Dendrimers are similar in size to a variety of biological structures; for example, fifth-generation polyamidoamine (PAMAM) dendrimers are similar in size and shape to haemoglobin (5.5 nm diameter). Each generation of dendrimer is described in terms of size, shape, molecular weight, and the number of surface functional groups, with increasing growth specified in terms of 'generation number.' In contrast, Hawker and Frechet were the first to report the convergent approach. A stepwise repeating reaction strategy is used to synthesize dendrimers radically from a central core. The value of dendrimers as drug carriers is discussed in this paper. The information presented in this article can provide useful references for further studies on making dendrimers and applications.

The potential role of prebiotics, probiotics, and synbiotics in adjuvant cancer therapy especially colorectal cancer

Cancer is a global health issue that is rising swiftly with younger people and an increased number of patients. The role of human microbiota in the pathophysiology of tumors has been paid more and more attention. Microecologics including prebiotics, probiotics, and synbiotics are among the best validated/proven resources for the application of microbiological prophylaxis and therapy. There is strong evidence that microecologics have anti-cancer activity and their potential association with cancer is significant. In this review, we will focus on the role of prebiotics, probiotics, and synbiotics in tumor suppression in maintaining the colon barrier, metabolism, immune regulation, inhibition of host tumor cell proliferation, and epidemiological-based recommendations. Besides, other signs illuminate the role of microecological agents to adjunct the cancer treatment and counter the toxic side effects of cancer drugs. In addition, we will explore their role in chemotherapy, where these probiotics can be used as an adjunct to chemotherapy, counteracting the toxic side effects of chemotherapy drugs to minimize or optimize the therapeutic effect. In the treatment of cancer, we can see the role of prebiotics, probiotics, synbiotics, and their application in cancer patients, and the effectiveness effect can be considered as a clinical benefit. PRACTICAL APPLICATIONS: A large number of studies have shown that microecologics including prebiotics, probiotics, and synbiotics play an important role in regulating intestinal microecology and contribute to the prevention and treatment of cancer, indicating that prebiotics, probiotics, and synbiotics have the potential to be used as microecological modulators in the adjuvant therapy of cancer. However, it is not clear what is the anti-tumor mechanism of these microecologics and how they antagonize the side effects of cancer chemotherapy and protect normal cells. This paper reviews the role of prebiotics, probiotics, and synbiotics in tumor suppression in maintaining the colon barrier, metabolism, immune regulation, and prevention of rapid growth of host cells, as well as their potential role in cancer chemotherapy. This review helps to better understand the relationship between prebiotics, probiotics, and synbiotics with immune regulation, intestinal microecology, metabolic regulation, and cell proliferation and provides strong evidence for their potential application as microecologics in cancer adjuvant therapy.

Influence of Initial pH Value on the Adsorption of Reactive Black 5 Dye on Powdered Activated Carbon: Kinetics, Mechanisms, and Thermodynamics

The aim of this work was to investigate the influence of initial pH value (pH₀) on the isothermal adsorption of Reactive Black 5 (RB5) dye on commercial powdered activated carbon. Four initial pH values were chosen for this experiment: pH₀ = 2.00, 4.00, 8.00, and 10.00. In order to investigate the mechanism of adsorption kinetic, studies have been performed using pseudo-first-order and pseudo-second-order kinetic models as well as an intraparticle diffusion model. In addition, thermodynamic parameters of adsorption were determined for pH₀ = 4.00. Results of this research showed that the initial pH value significantly influences the adsorption of RB5 dye onto activated carbon. The highest adsorption capacities (q_e) and efficiencies of decolouration were observed for initial pH values of pH₀ = 2.00 (q_e = 246.0 mg g⁻¹) and 10.00 (q_e = 239.1 mg g⁻¹) due to strong electrostatic interactions and attractive π···π interactions, respectively. It was also shown that the adsorption of RB5 dye on activated carbon at all initial pH values is kinetically controlled, assuming a pseudo-second-order model, and that intraparticle diffusion is not the only process that influences on the adsorption rate.

In situ utilization of biomass pretreatment liquor as a novel flocculant for anion dyes removal: Performance and mechanism

In this work, it was first found biomass pretreatment liquor (PL) produced from rice straw (RS) pretreatment with FeCl₃ and polyethylene glycol 400 co-solvent can be used in situ as a new flocculant to remove anionic dyes from wastewater. The removal performance of nine dyes was investigated using various PL doses at different pH values. The experiment indicated that the PL had different flocculation effects on these dyes (color removal efficiency: 42.58-99.84%). Positive color removal results for the dyes were unachievable with six commercial coagulants. Among the nine dyes treated by PL flocculation, the best removal efficiencies for color, turbidity and suspended matter were obtained for Congo red. In the flocculation process, Fe³⁺ plays a role in charge neutralization, lignin nanoparticles (LNP) relies on hydroxyl groups to react instantaneously with the amino groups on the dye, and are bridged together by π-π interactions to promote the formation of floc clusters until they completely settle. Utilization of PL as a flocculant helps pave the way to simultaneously treat waste biomass, waste treatment liquor and dye wastewater. This research is of great significance for future water environment remediation and material development.

Review of adsorption-membrane hybrid systems for water and wastewater treatment

Adsorption is an effective method for the removal of inorganic and organic contaminants and has been commonly used as a pretreatment method to improve contaminant removal and control flux during membrane filtration. Over the last two decades, many researchers have reported the use of hybrid systems comprising various adsorbents and different types of membranes, such as nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF) membranes, to remove contaminants from water. However, a comprehensive evaluation of the removal mechanisms and effects of the operating conditions on the transport of contaminants through hybrid systems comprising various adsorbents and NF, UF, or MF membranes has not been performed to date. Therefore, a systematic review of contaminant removal using adsorption-membrane hybrid systems is critical, because the transport of inorganic and organic contaminants via the hybrid systems is considerably affected by the contaminant properties, water quality parameters, and adsorbent/membrane physicochemical properties. Herein, we provide a comprehensive summary of the most recent studies on adsorption-NF/UF/MF membrane systems using various adsorbents and membranes for contaminant removal from water and wastewater and highlight the future research directions to address the current knowledge gap.

Adsorption, Equilibrium Isotherm, and Thermodynamic Studies towards the Removal of Reactive Orange 16 Dye Using Cu(I)-Polyaninile Composite

To overcome some of the limitations of activated carbon like efficiency, cost-effectiveness, and reusability, the present work deals with Cu(I)-based polyaniline (PANI) composite for the removal of reactive orange 16 (RO16) dye. Following the synthesis and characterization of formed Cu(I)-PANI composite, the batch experiments performed for the removal of RO16 dye indicated that the composite has the capacity to reduce the coloring from RO16. The experiments were conducted for the study of effects against changes in pH, time, and dose at room temperature, where we observed for a pH impact on the dye adsorption capacity in the range of 2–12. Among all, the optimal RO16 removal was found to be 94.77% at a pH of 4 and in addition, the adsorption kinetics confirmed to be pseudo-second-order with more suitability towards the Langmuir isotherm, where it is presumed to be the formation of a monolayer of dye molecule at the homogeneous absorbent surface. The calculated maximum capacity, q_m, determined from the Langmuir model was 392.156 mg/g. Further application of isotherms to attain thermodynamic parameters, a slight positive value of ΔS° for RO16 adsorption was observed, meaning that there is an increased randomness in the irregular pattern at the specific Cu(I)-PANI interface for an adsorption process. This mechanism plays an essential role in maintaining the effects of water pollution; and, based on the analysis therefore, it is prominent that the Cu(I)-PANI composite can be employed as a promising and economical adsorbent for the treatment of RO16 and other dye molecules from the sewage in wastewater.

Electrostatic Self-Assembly Synthesis of Three-Dimensional Mesoporous Lepidocrocite-Type Layered Sodium Titanate as a Superior Adsorbent for Selective Removal of Cationic Dyes via an Ion-Exchange Mechanism

Three-dimensional mesoporous lepidocrocite-type layered sodium titanate (LST) was constructed at room temperature by the electrostatic interaction between Ti_1-δO₂^4δ- nanosheets and Na⁺ ions. The results of a systematic X-ray diffraction investigation manifested the transition from the Ti_1-δO₂^4δ- nanosheets phase to the titanate/titania phase, which determined a phase diagram as a function of the temperature and NaCl concentration. In addition, scanning electron microscopy, inductively coupled plasma-mass spectrometry, thermogravimetric and differential thermal, N₂ adsorption-desorption, Raman spectroscopy, Fourier transform infrared spectroscopy, as well as ζ-potential analyses were utilized for adequate characterization of the LST physical and chemical properties. Furthermore, batch adsorption experiments demonstrated that LST had superior adsorption property and adsorption selectivity toward cationic dyes compared to those of anionic dyes. A multifarious influencing effect on the cationic dye adsorption behavior during the adsorption process was systematically investigated. Moreover, the pseudo-second-order kinetic model felicitously depicted the cationic dye adsorption behavior through an elaborate kinetic study, namely, chemisorption was the main adsorption action. Meanwhile, different adsorption isotherm models were utilized to process the experimental data, uncovering that the adsorption isotherms of cationic dyes on LST were suitable for a Langmuir isothermal model. More importantly, an ion-exchange mechanism was proposed for the cationic dye adsorption on LST, and the ion-exchange reaction occurred with a stoichiometric exchange between 1 mol of Na⁺ ions in the LST interlayer and 1 mol of MB molecules in the solution. In parallel, the electrochemical impedance spectroscopy and cyclic voltammogram measurements verified that the high ionic conductivity of Na⁺ ions in the LST interlayer resulted in a superior adsorption property. A two-step acid-base procedure was ultimately adopted to effectively regenerate LST adsorbent. This work provides not only an alternative adsorbent with superior adsorption capacity and adsorption selectivity but also some guiding significance for research on the adsorption mechanism of layered titanates.

Polyaspartate-Ionene/Na+-Montmorillonite Nanocomposites as Novel Adsorbent for Anionic Dye; Effect of Ionene Structure

Surface modification of sodium montmorillonite (Na+-Mt) was performed using antimicrobial agents to produce an ecofriendly nanocomposite. The adsorption performance of the nanocomposite has been evaluated for the removal of Acid Blue 25 dye (AB25) as a model organic pollutant from wastewater. Sodium montmorillonite (Na+-Mt) was modified with three different ionene compounds through ion exchange, and further modified through reaction with polyaspartate to provide three ecofriendly nanocomposites (denoted ICP-1-3). The nanocomposites were characterized using FTIR, PXRD, TEM, SEM, and BET surface area. The adsorption isotherm of AB25 onto ICP-1, ICP-2 and ICP-3 was analyzed using the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) models. The adsorption isotherm was found to be best fitted by a Freundlich model. The thermodynamic parameters were calculated. The kinetics of the adsorption data were analyzed and the adsorption behavior was found to obey pseudo-second-order kinetics, and the intraparticle diffusion model. The adsorption mechanism was studied by FTIR.

Preparation and Characterization of Activated Carbon Obtained from Water Treatment Plant Sludge for Removal of Cationic Dye from Wastewater

The proposal of this work was the preparation and characterization of activated carbons obtained from water treatment plant sludge (WTS) to apply as adsorbents in the removal of organic dye contaminants from wastewater. The activated carbons were produced with a combination of chemical activation and pyrolysis processes. The textural characteristics of both adsorbents presented a satisfactory superficial area and mesoporous structure. The presence of phenolic and carboxylic groups in the surface indicated a better adsorption of cationic adsorbates. When applied as adsorbents in the removal of methylene blue (MB) from wastewater, the maximum removal values obtained were up to 96%. The adsorption results showed that the adsorption was faster in the beginning and reached maximum around 30 min. The Elovich kinetic model and the Sips isotherm model presented the best fit to experimental data, which was checked by analysis of variance (ANOVA). The production of activated carbons from WTS is a sustainable and effective option in the removal of MB dye.

Synthesis of cellulose carbon aerogel via combined technology of wet ball-milling and TEMPO-mediated oxidation and its supersorption performance to ionic dyes

In this study, modified cellulose aerogels (CAs) were obtained via wet ball-milling and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation and were further applied to prepare cellulose-derived carbon aerogels (CCAs) by pyrolyzing. The results showed that the successive treatments by ball-milling and oxidation completely opened the CA fibers and converted them into plane or wrinkle structures. CCAs contained porous and graphite-like structures and its specific surface area reached up to 2825 m²/g. The maximum adsorption capacities of CCAs were 1078 mg/g for methylene blue (MB) and 644 mg/g for alizarin reds (ARS). The sorption of dyes occurred via hydrophobic partition, pore-filling, H-bonding, p/π-π electron donor-acceptor interactions. For the cationic MB, electrostatic attraction reinforced the sorption, while the electrostatic repulsion between the anionic ARS and CCAs was weakened by high salty. Besides, CCAs showed excellent salt tolerance. The present study provides an excellent CCA adsorbent by successive modification of ball-milling and oxidation of CAs.

Precoating membranes with submicron super-fine powdered activated carbon after coagulation prevents transmembrane pressure rise: Straining and high adsorption capacity effects

Commercially available powdered activated carbon (PAC) with a median diameter of 12-42 μm was ground into 1 μm sized superfine PAC (SPAC) and 200 nm sized submicron SPAC (SSPAC) and investigated as a pretreatment material for the prevention of hydraulically irreversible membrane fouling during a submerged microfiltration (MF) process. Compared with PAC and SPAC, SSPAC has a high capacity for selective biopolymer adsorption, which is a characteristic found in natural organic matter and is commonly considered to be a major contributor to membrane fouling. Precoating the membrane surface with SSPAC during batch filtration further removes the biopolymers by straining them out. In lab-scale membrane filtration experiments, an increase in the transmembrane pressure (TMP) was almost completely prevented through a precoating with SSPAC based on its pulse dose after coagulation pretreatment. The precoated SSPAC formed a dense layer on the membrane preventing biopolymers from attaching to the membrane. Coagulation pretreatment enabled the precoated activated carbon to be rinsed off during hydraulic backwashing. The functionality of the membrane was thereby retained for a long-term operation. Precoating the membranes with SSPAC after coagulation is a promising way to control membrane fouling, and efficiently prevents an increase in the TMP because of the straining effect of the SSPAC and the high capacity of the SSPAC to adsorb any existing biopolymers.

A water resistance magnetic graphene-anchored zeolitic imidazolate framework for efficient adsorption and removal of residual tetracyclines in wastewater

Water-resistant magnetic graphene-anchored zeolite imidazolate (Fe₃O₄/ZIF-8-G) composite materials with the largest surface area are formed by directly growing a hydrophobic ZIF-8 skeleton onto a graphene support through self-assembly in methanol. Fe₃O₄/ZIF-8-G hybrid composite has water resistance and super strong adsorption capacity, and is used as an effective adsorbent for adsorption and removal of residual tetracycline in wastewater. The morphologies and structure, as well as water resistance of Fe₃O₄/ZIF-8-G, were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry analysis (TGA), N₂ adsorption and pH_PZC. The adsorption for tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) followed pseudo-second-order kinetics and fitted the Freundlich adsorption model with the simultaneous adsorption capacity for TC (382.58 mg g^-1), OTC (565.94 mg g^-1) and CTC (608.06 mg g^-1) at pH 5-6 for 10 h. These were much higher than previously reported results for the removal of tetracycline from aqueous solutions. The used Fe₃O₄/ZIF-8-G could be effectively reused and recycled at least five times without significant loss of adsorption capacity. The hydrophobic and π-π interaction between the aromatic rings of TCs and the aromatic imidazole rings of the ZIF-8-G framework were the main adsorption mechanism on the surface of Fe₃O₄/ZIF-8-G. Constructing a hydrophobic surface of ZIF-8/G framework resulted in a reduction of the hydrophilic sites of the surface. This can improve stability and selective adsorption of ZIF-8-G framework. In addition, the results show no significant difference in the adsorption kinetics and adsorption capacity of Fe₃O₄/ZIF-8-G for TC, OTC and CTC in pure water and wastewater.

Cu(II)-enhanced degradation of acid orange 7 by Fe(II)-activated persulfate with hydroxylamine over a wide pH range

The activation of persulfate by Fe(II) coupled with hydroxylamine (the HA/Fe(II)/PS system) was highly effective for the degradation of refractory organic contaminants under acidic pH conditions. However, owing to the precipitation of ferric hydroxide and/or the slow reduction from Fe(III) to Fe(II), the HA/Fe(II)/PS system was invalid under neutral and alkaline pH conditions. In this study, it was observed that the degradation of acid orange 7 (AO7) was strongly enhanced over the wide pH range of 2-9 when trace Cu(II) (0.5-5 μM) was spiked into the HA/Fe(II)/PS system. It was evident that Cu(I) was generated via the reduction of Cu(II) by HA in the bimetallic system at both pH 3 and pH 8, and the steady concentration of Fe(II) in the bimetallic system was much higher than that in the HA/Fe(II)/PS system due to the rapid reaction between Fe(III) and Cu(I). Quenching experiments using tert-butyl alcohol, methanol and sodium bromide as the scavengers and electron spin resonance experiments confirmed that the primary reactive species responsible for AO7 degradation were sulfate radical at both pH 3 and pH 8, rather than hydroxyl radical and Cu(III). Nevertheless, sulfate radical was mainly produced by Fe(II)-activated PS at pH 3, while both Cu(I) and Fe(II) made important contributions to the generation of sulfate radical at pH 8. The bimetallic system was also highly effective in degrading other organic contaminants, such as phenol, diclofenac, reactive red 2 and orange G. This study might provide a promising idea based on Fe(II)-activated PS for degrading organic contaminants over a wide pH range.

A new biocompatible ternary Layered Double Hydroxide Adsorbent for ultrafast removal of anionic organic dyes

It would be of great significance to introduce a new biocompatible Layered Double Hydroxide (LDH) for the efficient remediation of wastewater. Herein, we designed a facile, biocompatible and environmental friendly layered double hydroxide (LDH) of NiFeTi for the very first time by the hydrothermal route. The materialization of NiFeTi LDH was confirmed by FTIR, XRD and Raman studies. BET results revealed the high surface area (106 m²/g) and the morphological studies (FESEM and TEM) portrayed the sheets-like structure of NiFeTi nanoparticles. The material so obtained was employed as an efficient adsorbent for the removal of organic dyes from synthetic waste water. The dye removal study showed >96% efficiency for the removal of methyl orange, congo red, methyl blue and orange G, which revealed the superiority of material for decontamination of waste water. The maximum removal (90%) of dyes was attained within 2 min of initiation of the adsorption process which supported the ultrafast removal efficiency. This ultrafast removal efficiency was attributed to high surface area and large concentration of -OH and CO₃²⁻ groups present in NiFeTi LDH. In addition, the reusability was also performed up to three cycles with 96, 90 and 88% efficiency for methyl orange. Furthermore, the biocompatibility test on MHS cell lines were also carried which revealed the non-toxic nature of NiFeTi LDH at lower concentration (100% cell viability at 15.6 μg/ml). Overall, we offer a facile surfactant free method for the synthesis of NiFeTi LDH which is efficient for decontamination of anionic dyes from water and also non-toxic.

Functionalized Leather: a Novel and Effective Hazardous Solid Waste Adsorbent for the Removal of the Diazo Dye Congo Red from Aqueous Solution

The leather industry produces a high yield of solid hazardous wastes that generate a major impact on the environment. At the same time, the use of dyes by different manufacturing industries, including the footwear industry, creates large amounts of colored wastewater that is hard to treat. In this paper, potential adsorbents based on the functionalization of solid waste from leather in the removal of anionic dye Congo Red were studied. Twelve different functionalized adsorbents were analyzed in terms of dye removal. From those, the best adsorbents were characterized and tested to determine their life cycle, pH dependency and the resulting phytotoxicity of the treated dye baths. Different kinetic models were evaluated to describe this adsorption process. It was found that functionalized leather adsorbents presented multi-linearity behavior when removing Congo Red. Life cycle analysis showed that the adsorbents presented a high yield of absorption until the third cycle of operation, while phytotoxicity tested showed reductions up to 50% in the toxicity of the treated dye baths.

Submerged membrane adsorption hybrid system using four adsorbents to remove nitrate from water

Nitrate contamination of ground and surface waters causes environmental pollution and human health problems in many parts of the world. This study tests the nitrate removal efficiencies of two ion exchange resins (Dowex 21K XLT and iron-modified Dowex 21K XLT (Dowex-Fe)) and two chemically modified bio-adsorbents (amine-grafted corn cob (AG corn cob) and amine-grafted coconut copra (AG coconut copra)) using a dynamic adsorption treatment system. A submerged membrane (microfiltration) adsorption hybrid system (SMAHS) was used for the continuous removal of nitrate with a minimal amount of adsorbents. The efficiency of membrane filtration flux and replacement rate of adsorbent were studied to determine suitable operating conditions to maintain the effluent nitrate concentration below the WHO drinking standard limit of 11.3 mg N/L. The volume of water treated and the amount of nitrate adsorbed per gramme of adsorbent for all four flux tested were in the order Dowex-Fe > Dowex > AG coconut copra > AG corn cob. The volumes of water treated (L/g adsorbent) were 0.91 and 1.85, and the amount of nitrate removed (mg N/g adsorbent) were 9.8 and 22.2 for AG corn cob and Dowex-Fe, respectively, at a flux of 15 L/(m²/h).

Understanding azo dye anaerobic bio-decolorization with artificial redox mediator supplement: Considering the methane production

Artificial redox mediators (ARM) have been proven to accelerate the azo dye anaerobic bio-reduction (ADAB) but the mechanisms involved are still unclear. Previous studies do seldom focus on the production of methane during the ADAB, particularly if supplemented with ARM. Our studies revealed that the supplement of ARM could significantly accelerate the decolorization rate, recover the inhibited methanogenesis and decrease extracellular polymeric substance secretion in an ADAB system. Supplement of an ARM only enhanced the pre-existing metabolic pathway of the ADAB system. Significant differences in metabolic pathway and microbial community were found between traditional methanogenic system and ADAB system by high-throughput sequencing technique. The ADAB system performed an "over-requirement for electron donor" phenomenon and the requirement amount can be altered by regulating ARM dosage. Response surface methodology was then successfully employed to optimize the dosage of ARM and possible additional electron donor required for ADAB under different conditions.

Multifunctional PMMA@Fe₃O₄@DR Magnetic Materials for Efficient Adsorption of Dyes

Magnetic porous microspheres are widely used in modern wastewater treatment technology due to their simple and quick dye adsorption and separation functions. In this article, we prepared porous polymethylmethacrylate (PMMA) microspheres by the seed-swelling method, followed by in situ formation of iron oxide (Fe₃O₄) nanoparticles within the pore. Then, we used diazo-resin (DR) to encapsulate the porous magnetic microspheres and achieve PMMA@Fe₃O₄@DR magnetic material. We studied the different properties of magnetic microspheres by different dye adsorption experiments before and after the encapsulation and demonstrated that the PMMA@Fe₃O₄@DR microspheres can be successfully used as a reusable absorbent for fast and easy removal of anionic and aromatic dyes from wastewater and can maintain excellent magnetic and adsorption properties in harsh environments.

Bioremediation and Detoxification of the Textile Wastewater with Membrane Bioreactor Using the White-rot Fungus and Reuse of Wastewater

BACKGROUND

Application of membrane technology to wastewater treatment has expanded over the last decades due to increasingly stringent legislation, greater opportunities for water reuse/recycling processes and continuing advancement in membrane technology.

OBJECTIVES

In the present study, a bench-scale submerged microfiltration membrane bioreactor (MBR) was used to assess the treatment of textile wastewater.

MATERIALS AND METHODS

The decolorization capacity of white-rot fungus coriolus versicolor was confirmed through agar plate and liquid batch studies. The temperature and pH of the reactor were controlled at 29±1°C and 4.5±2, respectively. The bioreactor was operated with an average flux of 0.05 m.d^-1 (HRT=15hrs) for a month.

RESULTS

Extensive growth of fungi and their attachment to the membrane led to its fouling and associated increase of the transmembrane pressure requiring a periodic withdrawal of sludge and membrane cleaning. However, stable decoloration activity (approx. 98%), BOD (40-50%), COD (50-67%) and total organic carbon (TOC) removal (>95%) was achieved using the entire system (fungi + membrane), while the contribution of the fungi culture alone for TOC removal, as indicated by the quality of the reactor supernatant, was 35-50% and 70%, respectively.

CONCLUSIONS

The treated wastewater quality satisfied the requirement of water quality for dyeing and finishing process excluding light coloration. Therefore, textile wastewater reclamation and reuse is a promising alternative, which can both conserve or supplement the available water resource and reduce or eliminate the environmental pollution.