Feasibility analysis of color removal from textile dyeing wastewater in a fixed-bed column system by surfactant-modified zeolite (SMZ)

Research Enhancing Acidic Mine Wastewater Purification: Innovations in Red Mud-Loess

This study investigates the adsorption of cadmium (Cd) by red mud-loess mixed materials and assesses the influence of quartz sand content on permeability. Shear tests are conducted using various pore solutions to analyze shear strength parameters. The research validates solidification methods for cadmium-contaminated soils and utilizes SEM-EDS, FTIR, and XRD analysis to elucidate remediation mechanisms. The findings suggest that the quartz sand content crucially affects the permeability of fine-grained red mud-loess mixtures. The optimal proportion of quartz sand is over 80%, significantly enhancing permeability, reaching a coefficient of 6.7 × 10-4 cm/s. Insufficient quartz sand content of less than 80% fails to meet the barrier permeability standards, leading to a reduced service life of the engineered barrier. Adsorption tests were conducted using various pore solutions, including distilled water, acidic solutions, and solutions containing Cd, to evaluate the adsorption capacity and shear characteristics of the red mud-loess mixture. Additionally, the study examines the behavior of Cd-loaded red mud-loess mixtures in various pore solutions, revealing strain-hardening trends and alterations in cohesiveness and internal friction angle with increasing Cd concentrations. The analysis of cement-red mud-loess-solidified soil demonstrates enhancements in soil structure and strength over time, attributed to the formation of crystalline structures and mineral formations induced by the curing agent. These findings provide valuable insights into the remediation of cadmium-contaminated soils.

A review on the application of nanoporous zeolite for sanitary landfill leachate treatment

This review deals with low-cost nanoporous zeolites for the treatment of sanitary landfill leachate. Organic contaminants and ammoniacal nitrogen are significant parameters in landfill leachate treatment. Adsorption processes are regarded as promising alternative treatment options in this respect. Zeolites are aluminosilicate materials that are widely used in separation, filtration, adsorption and catalysis. Natural zeolite is a low-cost and readily available form of zeolite and is a promising candidate to be used as an ion-exchange material for ammonia and other inorganic pollutant removal from landfill leachate. In this review, adsorption isotherms and kinetic models in batch systems are evaluated and adsorption design parameters of the fixed-bed system are presented. Studies on ammonia removal from landfill leachate via zeolites have been thoroughly investigated. Leachate treatment systems combined with zeolites are presented. Cost of zeolites are also reported in comparison with other adsorbents. The investigated studies demonstrate that activated zeolite can improve the removal of chemical oxygen demand, NH₃-N and colour significantly compared to the case where raw zeolite is used. Moreover, the composite of activated carbon and zeolite is also favorable for ammonia removal according to reported findings, where best adsorptive removal is attained on the composite media (24.39 mg/g).

Solvent impregnated resins for the treatment of aqueous solutions containing different compounds: a review

In this review paper, a complete study and analysis of the research articles dealing with the removal of various organic and inorganic pollutants using solvent impregnated resins (SIR) is carried out. The method of impregnation, characterizations of prepared resin, and regeneration techniques of different SIRs for batch and continuous fixed bed columns are presented. The effects of different operating parameters (e.g., loading of solvent on the resin, dosage of adsorbent, initial solute concentration, pH, temperature, time, ionic strength) on the separation efficiency of SIR in the batch mode are discussed. Thermodynamic parameters (change in Gibbs free energy, enthalpy, and entropy) are tabulated from the data available in the literature, and if not given, then their values are calculated and presented. The influence of parameters (flow rate, bed height, pH, concentration of the solution, etc.) on the fixed bed column performance is analyzed. Design aspects of the column are also discussed, and the dimensions of fixed bed columns for industrial applications are proposed.

Pollution, Toxicity and Carcinogenicity of Organic Dyes and their Catalytic Bio-Remediation

Water pollution due to waste effluents of the textile industry is seriously causing various health problems in humans. Water pollution with pathogenic bacteria, especially Escherichia coli (E. coli) and other microbes is due to the mixing of fecal material with drinking water, industrial and domestic sewage, pasture and agricultural runoff. Among the chemical pollutants, organic dyes due to toxic nature, are one of the major contaminants of industrial wastewater. Adequate sanitation services and drinking quality water would eliminate 200 million cases of diarrhea, which results in 2.1 million less deaths caused by diarrheal disease due to E. coli each year. Nanotechnology is an excellent platform as compared to conventional treatment methods of water treatment and remediation from microorganisms and organic dyes. In the current study, toxicity and carcinogenicity of the organic dyes have been studied as well as the remediation/inactivation of dyes and microorganism has been discussed. Remediation by biological, physical and chemical methods has been reviewed critically. A physical process like adsorption is cost-effective, but can't degrade dyes. Biological methods were considered to be ecofriendly and cost-effective. Microbiological degradation of dyes is cost-effective, eco-friendly and alternative to the chemical reduction. Besides, certain enzymes especially horseradish peroxidase are used as versatile catalysts in a number of industrial processes. Moreover, this document has been prepared by gathering recent research works related to the dyes and microbial pollution elimination from water sources by using heterogeneous photocatalysts, metal nanoparticles catalysts, metal oxides and enzymes.

Green fabrication of ZnO nanoparticles using Eucalyptus spp. leaves extract and their application in wastewater remediation

The present study explored removal of carcinogenic cationic and anionic dyes from aqueous medium using green fabricated zinc oxide nanoparticles (ZnO-NPs). The ZnO-NPs were synthesized employing biogenic green reduction and precipitation approach. The characterization of ZnO NPs was done using various techniques such as FESEM, XRD, BET, TGA, HRTEM, EDX, and FTIR. All experiments were conducted in batch mode. Maximum removal was achieved at pH 6.0 and pH 8.0 for Congo Red (CR) and Malachite Green (MG) dyes respectively. Dye adsorption process showed better fit with Langmuir and Temkin isotherm models for CR dye and MG dye respectively. Maximum adsorption capacity of ZnO NPs was 48.3 mg/g for CR dye and 169.5 mg/g for MG dye. The dye adsorption followed pseudo-second order model and values of thermodynamic parameters confirmed that the adsorption process was spontaneous and favourable. Reusability efficiency of the nanoparticle was explored using ethanol and water and based on results it was inferred that ZnO-NPs can be reused for dye removal. Effect of salinity on the removal of CR and MG dyes was also explored and found that presence of salinity in aqueous medium have adverse impact on the dye removal efficiency of ZnO-NPs.

Microbial degradation, spectral analysis and toxicological assessment of malachite green by Streptomyces chrestomyceticus S20

Malachite green (MG), a triphenylmethane dye is extensively used for coloring silk, aquaculture and textile industries, it has also has been reported toxic to life forms. This study aimed to investigate the biodegradation potential of MG by actinobacteria. The potent actinobacterial strain S20 used in this study was isolated from forest soil (Sabarimala, Kerala, India) and identified as Streptomyces chrestomyceticus based on phenotype and molecular features. Strain S20 degraded MG up to 59.65 ± 0.68% was studied in MSM medium and MG (300 mg l^-1) and degradation was increased (90-99%) by additions of 1% glucose and yeast extract into the medium at pH 7. The treated metabolites from MG by S20 characterized by FT-IR and GC-MS. The results showed MG has been degraded into nontoxic compounds evaluated by (1) phytotoxic assay on Vigna radiata, (2) microbial toxicity on Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Streptococcus sp. and Escherichia coli, (3) cytotoxicity assay in a human cell line (MCF 7). The toxicity studies demonstrated that the byproducts from MG degradation by S. chrestomyceticus S20 were no toxic to plants and microbes and less toxic to human cells as compared to the parent MG. Perhaps this is the first work reported on biodegradation of MG by S. chrestomyceticus which could be a potential candidate for the removal of MG from various environments.

Nano-engineered Adsorbent for the Removal of Dyes from Water: A Review

Background:

The huge quantity of wastewater, containing poisonous and hazardous dyes, is released by various industries which pollute water in direct and indirect ways. Most of the dyes are a dangerous class of water contaminants which have affected the environment drastically. Some dyes such as congo red, rhodamine B, methylene blue, methyl violet, and crystal violet are a serious threat to human beings.

Remediation Method:

Numerous methods are available for the removal of dyes from water. Adsorption, being a superior and eco-friendly technique, has advantage of eliminating organic dyes because of the availability of materials as adsorbents. The inexpensive nanomaterials are a more attractive choice for remediation of various dyes due to their unique properties and offer an adequate pathway to adsorb any organic dye from water to overcome its hazardous effects on human health.

Results:

In this review, we have discussed the latest literature related to various types of synthesis, characterization and uses as adsorbent for highly adsorptive removal capacity of nanoparticles for organic dyes.

Conclusion:

Adsorption technology provides an attractive pathway for further research and improvement in more efficient nanoparticles, with higher adsorption capacity, for numerous dyes to eliminate the dyes discharged from various industries and thus reduce the contamination of water. Therefore, nanocomposites may contribute to future prospective water treatment process.

Adsorption and desorption cycles of reactive blue BF-5G dye in a bone char fixed-bed column

In the textile industry, the amount of dye unfixed in fabrics is discarded with wastewaters. Effluents of this nature can be treated efficiently by adsorption on activated bone char, but the reuse of adsorbent is necessary for the technique to be economically feasible. Therefore, the objective of this work was to study the process of desorption of BF-5G blue dye from a bone char fixed-bed column. Solutions of sodium chloride, acetic acid and ethyl alcohol were tested as regenerating agents. Due to the hydrophobicity effect of organic solvent molecules, the highest desorption capacity was observed for ethyl alcohol solution, and the fixed bed was reused after six cycles of adsorption. The other solutions did not promote significant desorption. The results showed that adsorption of the dye involved irreversible interactions between adsorbate molecules and bone char. However, the use of acetic acid solution resulted in the neutralisation of some of the adsorbent surface charges, allowing the fixed bed to operate for a longer time in the second cycle than in the first.

Adsorption of methyl tert-butyl ether (MTBE) onto ZSM-5 zeolite: Fixed-bed column tests, breakthrough curve modelling and regeneration

ZSM-5, as a hydrophobic zeolite, has a good adsorption capacity for methyl tert-butyl ether (MTBE) in batch adsorption studies. This study explores the applicability of ZSM-5 as a reactive material in permeable reactive barriers (PRBs) to decontaminate the MTBE-containing groundwater. A series of laboratory scale fixed-bed column tests were carried out to determine the breakthrough curves and evaluate the adsorption performance of ZSM-5 towards MTBE under different operational conditions, including bed length, flow rate, initial MTBE concentration and ZSM-5 dosage, and regeneration tests were carried out at 80, 150 and 300 °C for 24 h. Dose-Response model was found to best describe the breakthrough curves. MTBE was effectively removed by the fixed-bed column packed with a ZSM-5/sand mixture with an adsorption capacity of 31.85 mg g^-1 at 6 cm bed length, 1 mL min^-1 flow rate, 300 mg L^-1 initial MTBE concentration and 5% ZSM-5 dosage. The maximum adsorption capacity increased with the increase of bed length and the decrease of flow rate and MTBE concentration. The estimated kinetic parameters can be used to predict the dynamic behaviour of column systems. In addition, regeneration study shows that the adsorption capacity of ZSM-5 remains satisfactory (>85%) after up to four regeneration cycles.

The role of surfactants in wastewater treatment: Impact, removal and future techniques: A critical review

Wastewater treatment has an important responsibility to react to changing consumer and industrial produced wastes that pose environmental challenges. Surfactants are one of these emerging contaminants. They are of interest because of their increasingly ubiquitous domestic and industrial use and the difficulty their presence causes traditional treatment. In response to this developing area, this critical review considers research from a variety of technical backgrounds to provide an up to date overview of the impact of surfactants on the environment, health and their removal. This found major concerns about surfactants on the environment and on health being corroborated in the past five years. Current research into removal focuses on existing biological and chemical wastewater treatment optimisation. Despite improvements being found to traditional biological methods using chemical pre-treatments there is a clear lack of consensus regarding the ideal strategy. Drawbacks and potential solutions for a range of these technologies, including Fenton reaction and aerobic degradation, are discussed. In this field the authors recommend an improved diversity in surfactants used for the research and addressing of significant knowledge gaps. Novel methods, such as Carbon Nanotube (CNT) use are also discussed. These methods, while showing promising results, will require continual research effort to resolve present issues such as variable performance and environmental concerns. Larger scale work is also needed to validate the initial work done. Potential uses of surfactants to optimise wastewater treatment, such as Surfactant Modified Zeolites (SMZs), are also discussed. This review finds that surfactant removal from wastewater is a promising and challenging field that warrants further investigation.

Adsorption of reactive red dye (RR-120) on nanoadsorbent O-carboxymethylchitosan/γ-Fe2O3: kinetic, equilibrium and factorial design studies

In this study, a novel magnetically separable nanoadsorbent, consisting of a γ-Fe₂O₃ and O-carboxymethylchitosan (O-CM), was synthesized in a three-step procedure.

Determination of methylene blue biosorption by Rhizopus arrhizus in the presence of surfactants with different chemical structures

Methylene blue (MB) biosorption properties of Rhizopus arrhizus were investigated in the presence of surfactants. The effects of cationic and anionic surfactants on MB removal by dead biomass (1 g L(-1)) were determined. MB removal was tested as a function of initial pH (2-12), contact time (5-1440 min), and dye (37.4-944.7 mg L(-1)) and surfactant (0-10 mM) concentrations. The opposite charged anionic surfactant dodecylbenzenesulfonic acid sodium salt (DBS) enhanced sorption of cationic MB by biomass dramatically. Maximum biosorption capacity was 471.5 mg g(-1) at pH 8 with 0.5 mM DBS at 944.7 mg L(-1) MB concentration. The surfactant-stimulated fungal decolorization method may provide a highly efficient, inexpensive, and time-saving procedure in biological wastewater treatment technologies.

A novel adsorbent of Na(2)Ta(2)O(6) porous microspheres with F(-) gradient concentration distribution: high cationic selectivity and well-regulated recycling

Pyrochlore Na2Ta2O6 porous microspheres with F(-) gradient concentration distribution were first prepared, which showed an excellent selectivity toward cationic dyes as an adsorbent. These dyes were regenerated rapidly by adding to NaAc solution. After then, the adsorbent still showed a high adsorption capacity. Optionally, the effective recycling of the adsorbents was achieved by UV light illumination, free of secondary environmental contamination. The rate of adsorption reaction followed the pseudo second-order kinetics, and the sorption isotherm well fitted to the Freundlich isotherm model. Eventually, the adsorption reaction for the absorbents was found to be a spontaneous and endothermic process.

Removal of sulfamethoxazole and sulfapyridine by carbon nanotubes in fixed-bed columns

Sulfamethoxazole (SMX) and sulfapyridine (SPY), two representative sulfonamide antibiotics, have gained increasing attention because of the ecological risks these substances pose to plants, animals, and humans. This work systematically investigated the removal of SMX and SPY by carbon nanotubes (CNTs) in fixed-bed columns under a broad range of conditions including: CNT incorporation method, solution pH, bed depth, adsorbent dosage, adsorbate initial concentration, and flow rate. Fixed-bed experiments showed that pH is a key factor that affects the adsorption capacity of antibiotics to CNTs. The Bed Depth Service Time model describes well the relationship between service time and bed depth and can be used to design appropriate column parameters. During fixed-bed regeneration, small amounts of SMX (3%) and SPY (9%) were irreversibly bonded to the CNT/sand porous media, thus reducing the column capacity for subsequent reuse from 67.9 to 50.4 mg g(-1) for SMX and from 91.9 to 72.9 mg g(-1) for SPY. The reduced column capacity resulted from the decrease in available adsorption sites and resulting repulsion (i.e., blocking) of incoming antibiotics from those previously adsorbed. Findings from this study demonstrate that fixed-bed columns packed with CNTs can be efficiently used and regenerated to remove antibiotics from water.

Heavy metal removal by combining anaerobic upflow packed bed reactors with water hyacinth ponds

The removal of four selected heavy metals (Cu, Cd, Pb and Zn) has been assessed in an upflow anaerobic packed bed reactor filled with porous volcanic rock as an adsorbent and an attachment surface for bacterial growth. Two different feeding regimes were applied using low (5 mg L(-1) of heavy metal each) and high (10 mg L(-1) of heavy metal each) strength wastewater. After a start-up and acclimatization period of 44 days, each regime was operated for a period of 10 days with a hydraulic retention time of one day. Good removal efficiencies of at least 86% were achieved for both the low and high strength wastewater. A subsequent water hyacinth pond with a hydraulic retention time of one day removed an additional 61% Cd, 59% Cu, 49% Pb and 42% Zn, showing its importance as a polishing step. The water hyacinth plant in the post-treatment step accumulated heavy metals mainly in the root system. Overall metal removal efficiencies at the outlet of the integrated system were 98% for Cd, 99% for Cu, 98% for Pb and 84% for Zn. Therefore, the integrated system can be used as an alternative treatment system for metal-polluted wastewater, especially in developing countries.

Variation in performance of surfactant loading and resulting nitrate removal among four selected natural zeolites

Surfactant modified zeolites (SMZs) have the capacity to target various types of water contaminants at relatively low cost and thus are being increasingly considered for use in improving water quality. It is important to know the surfactant loading performance of a zeolite before it is put into application. In this work we compare the loading capacity of a surfactant, hexadecyltrimethylammonium bromide (HDTMA-Br), onto four natural zeolites obtained from specific locations in the USA, Croatia, China, and Australia. The surfactant loading is examined using thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. We then compare the resulting SMZs performance in removing nitrate from water. Results show that TGA is useful to determine the HDTMA loading capacity on natural zeolites. It is also useful to distinguish between a HDTMA bi-layer and a HDTMA mono-layer on the SMZ surface, which has not been previously reported in the literature. TGA results infer that HDTMA (bi-layer) loading decreases in the order of US zeolite>Croatian zeolite>Chinese zeolite>Australian zeolite. This order of loading explains variation in performance of nitrate removal between the four SMZs. The SMZs remove 8-18 times more nitrate than the raw zeolites. SMZs prepared from the selected US and Croatian zeolites were more efficient in nitrate removal than the two zeolites commercially obtained from Australia and China.

Removal of humic acid from aqueous solution by cetylpyridinium bromide modified zeolite

Natural zeolite was modified by loading cetylpyridinium bromide (CPB) to create more efficient sites for humic acid (HA) adsorption. The natural and CPB modified zeolites were characterized with X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. The effects of various experimental parameters such as contact time, initial HA concentration, solution pH and coexistent Ca2+, upon HA adsorption onto CPB modified zeolites were evaluated. The results showed that natural zeolite had negligible affinity for HA in aqueous solutions, but CPB modified zeolites exhibited high adsorption efficiency for HA. A higher CPB loading on natural zeolites exhibited a larger HA adsorption capacity. Acidic pH and coexistent Ca2+ were proved to be favorable for HA adsorption onto CPB modified zeolite. The kinetic process was well described by pseudo second-order model. The experimental isotherm data fitted well to Langmuir and Sips models. The maximum monolayer adsorption capacity of CPB modified zeolite with surfactant bilayer coverage was found to be 92.0 mg/g.