Hazardous Wastewater Treatment Research Articles

Three-Dimensional Reduced Graphene Oxide Hybrid Nano-Silver Scaffolds with High Antibacterial Properties.

In recent years, hazardous wastewater treatment has been a complex and global problem. In this work, by considering the antimicrobial activity of Ag nanoparticles (AgNPs) and reduced graphene oxide (rGO), we constructed an antibacterial device (G-AgNP) with AgNPs conformably deposited onto a 3D scaffold of reduced graphene oxide in situ. The major limitation, which is difficult to recycle, of two-dimensional graphene-silver composite materials in previous studies is improved. Characterization techniques, SEM, TEM, XRD, and XPS, confirmed the synthesis of nanocomposites. Attributed to its larger specific area, more active sites, and synergistic enhancement, the G-AgNP device demonstrated the best bacterial removal capacity, with an antibacterial rate for both E. coli and S. aureus as high as 100% at quite low AgNP contents. The reported G-AgNP has potential application as a wearable sewage treatment device and for the protection of wearable sensors as a promising sterilizing candidate based on its high and stable antibacterial efficiency.

Calcium Silicate Hydrate Cation-Exchanger from Paper Recycling Ash and Waste Container Glass

Synthetic 11 Å tobermorite (Ca5Si6O16(OH)2.4H2O) and its Al-substituted analogue are layer-lattice ion-exchangers with potential applications in nuclear and hazardous wastewater treatment. The present study reports the facile one-pot hydrothermal synthesis of an Al-tobermorite-rich cation-exchanger from a combination of paper recycling ash, post-consumer container glass, and lime, with compositional ratios of [Ca]/[Si + Al] = 0.81 and [Al]/[Si + Al] = 0.18. The reaction products were characterized by powder X-ray diffraction analysis, 29Si magic angle spinning nuclear magnetic resonance spectroscopy, and scanning electron microscopy. Hydrothermal processing in 4 M NaOH(aq) at 100 °C for 7 days yielded an Al-tobermorite-rich product that also contained katoite (Ca3Al2SiO12H8), portlandite (Ca(OH)2), calcite (CaCO3), and amorphous silicate gel. The hydrothermal product was found to have a Cs+ cation exchange capacity of 59 ± 4 meq 100 g−1 and selective Cs+ distribution coefficients (Kd) of 574 ± 13 and 658 ± 34 cm3 g−1 from solutions with molar ratios [Cs+]:[Na+] and [Cs+]:[Ca2+] of 1:100. In a batch sorption study at 20 °C, the uptakes of Pb2+, Cd2+, and Cs+ were determined to be 1.78 ± 0.04, 0.65 ± 0.06, and 0.36 ± 0.03 mmol g−1, respectively. The kinetics of Pb2+, Cd2+, and Cs+ removal were described by the pseudo-second-order rate model, which gave respective rate constants (k2) of 0.010, 0.027, and 1.635 g mmol−1 min−1, and corresponding correlation coefficients (R2) of 0.997, 0.996, and 0.999. The metal ion sorption properties of the tobermorite-rich product compared favorably with those of other waste-derived tobermorites reported in the literature. Potential strategies to improve the yield, crystallinity, and sorption characteristics of the product are discussed.

The investigation of activated carbon by K2CO3 activation: Micropores- and macropores-dominated structure

In this study, the K2CO3 activation of bamboo was investigated in detail, and the structure and properties of the prepared activated carbons were tested for the feasibility of CO2 capture application and the potential for both ion and bacteria adsorption for use in the field of hazardous wastewater treatment. Activated carbons were produced with different activator ratios, from 0.5 to 6 according to the sample mass ratio. The ratio of H or O to C (H/C or O/C) increased with the increasing amount of K2CO3 added for the activation. The samples had a highly-porous microporous structure, in which the micropore volume was calculated to be 0.6 cm3 g−1 by the DR method of the CO2 adsorption isotherm at 298 K. The BET surface area and total pore volume estimated from the N2 adsorption isotherms at 77 K of the activated materials increased according to the increase of the K2CO3 impregnation ratio to a maximum value of 1802 m2 g−1 and 0.91 cm3 g−1, respectively. Moreover, the K2CO3-activated samples had a specific morphology, that is, macropores which are presumed to be derived from bubbles. The X-ray-CT images showed that the bubble-like structure is not only on the surface but also inside the samples. The results of gas adsorption methods, mercury porosimetry, and SEM showed the co-existence of micropores (<2 nm) and macropores (100–10,000 nm). The results highlighted the unique pore structure, that is, the coexistence of micropores and macropores that would contribute to forming solutions for carbon sequestration in the atmosphere and wastewater treatment.

Comparative study of Pb2+, Ni2+, and methylene blue adsorption on spherical waste solid-based geopolymer adsorbents enhanced with carbon nanotubes

• Carbon nanotube/geopolymer spheres were obtained by spheroidization. • Pore structure and phase evolution of the spheres were affected by carbon nanotubes. • Adsorption performance was enhanced by carbon nanotubes. Spherical porous carbon nanotube-reinforced geopolymer (CNTs/GP) adsorbents were spheroidized in polyethylene glycol 400 solvent by combing carbon nanotubes (CNTs) with a fly ash and slag-based geopolymer slurry. The effects of CNTs on the phase evolution and pore structure of the CNTs/GP spheres and their adsorption behavior for methylene blue (MB) and heavy metals (Pb 2+ and Ni 2+ ) were evaluated. The CNTs/GP spheres had a perfect spherical shape and mesoporous structure. The spheres were composed of an amorphous phase and had a high BET surface area of 73.06 m 2 /g with 3 wt% CNTs. The addition of CNTs into the spheres enhanced the removal efficiency for the pollutants (Pb 2+ , Ni 2+ and MB). The calculated q m of the sphere with 3 wt% CNTs was 25.549 mg/g for MB, 52.743 mg/g for Pb 2+ ; and 8.915 mg/g for Ni 2+ . The adsorption data of the spheres were well obeyed the Langmuir isotherm model and pseudo-second-order kinetics model, suggesting that multiple mechanisms such as physisorption, chemisorption and ion exchange were involved. The CNTs/GP spheres also presented good cyclic regeneration properties; hence, they can be applied as potential adsorbents for the treatment of hazardous wastewater.

Hazardous wastewater treatment by low‐cost sorbent with in situ regeneration using hybrid solar energy‐electrochemical system

Hazardous industrial wastes negatively impact the environment by creating issues for aquatic as well as human's life. This study investigates the treatment of hazardous industrial wastewater using cost-effective graphite adsorbent along with electrochemical regeneration integrated with renewable solar energy. The synthetic industrial effluent containing crystal violet dye was treated using an adsorbent (Nyex™ 1000) having a surface area of 1.0m2 g-1 . The efficiency of removing solute was found to be more than 90%. The adsorbent regeneration efficiency was achieved at 99.5% by passing a charge of 100Cg-1 at current density of 10mAcm-2 for 1h. Solar energy was integrated with electrochemical reactor for the regeneration of adsorbent to make the system cost-effective and self-sustainable. PRACTITIONER POINTS: Industrial hazardous wastewater treatment with a cost-effective graphite integrated adsorbent. Development of renewable solar energy-integrated with electrochemical system for regeneration. Regeneration efficiency of adsorbent Nyex™ 1000 was achieved around 99.5% with integrated system. Sustainable system was introduced to incorporate with renewable energy for waste water treatment.

Synthesis of alginate-coated magnetic nanocatalyst containing high-performance integrated enzyme for phenol removal

Effluent containing phenol is hazardous wastewater for the environment and human health. In the current work, synthesis and characterization of a new bi-enzymatic, magnetic-core nanocatalyst was investigated, and its performance as nanocatalyst for phenol removal from wastewater was examined. The obtained data suggested that the maximum combination of Peroxidases (POD) and Polyphenol Oxidase (PPO) enzymes (CPPE) stabilization can be achieved at T = 20 °C, pH value of 8, glutehydrie concentration of 1.6%, and enzyme to nanoparticles ratio of 1:200. Furthermore, it was found that the immobilized enzymes had higher stability than free enzyme against change in pH, temperature and even their durability. The Immobilized enzymes were used for phenol removal, and 98.1% separation was observed after 145 min when H2O2 to phenol ratio was 1.2, and in high concentrations of phenol (in the range of 2–10 mM) in the presence of CPPE. Finally, the stabilized enzymes were used 7 times in the phenol removal process, and the enzymes retained about 50% of their initial activity after 6 uses. It seems that the CPPE-alginate nanocatalyst could be used in hazardous wastewater treatment in particular for phenol removal.

Mixed matrix membranes incorporated with sonication-assisted ZIF-8 nanofillers for hazardous wastewater treatment

Mixed matrix membranes (MMMs) provide a unique pathway to treat hazardous industrial effluents. MMMs containing zeolitic imidazolate framework-8 (ZIF-8) as filler in polydimethoxysilane (PDMS) matrix were synthesized. ZIF-8 was prepared using a modified recipe and characterized by different techniques to evaluate its morphology, thermal stability, surface area, pore volume, and other characteristics. The performance of membranes was evaluated for their application in industrial dye-stuff wastewater treatment and solvent-resistant nanofiltration. The results demonstrated that increase in the percentage of ZIF-8 loading in PDMS led to simultaneous increase in the solvent permeability as well as solute rejection from wastewater. The permeability of MMMs increased up to 32% as compared with neat PDMS membrane. The organic dye rejection was achieved more than 87% with MMMs incorporated with 20% loading of nanofillers. Rejection of MMMs was 22% higher than that of unfilled PDMS membrane due to the effect of reduced polymer swelling and size exclusion of the nanofillers. Membrane swelling tests with toluene and isopropanol demonstrated that nanofiller amount has inverse relation with membrane swelling, which implied that nanofillers were in good interaction with polymer and allowed defect free membranes with higher solute rejections and reduced membrane swelling.

Membrane photo-bioreactor coupled with heterogeneous Fenton fluidized bed for high salinity wastewater treatment: Pollutant removal, photosynthetic bacteria harvest and membrane anti-fouling analysis

In this study, efficient photosynthetic bacteria (PSB)-GO/PVDF membrane photo-bioreactor (MPBR) combined with heterogeneous Fenton fluidized bed was built and successfully applied for treatment of actual refractory seafood-processing wastewater with extremely high salinity. As effective pre-treatment, heterogeneous Fenton was designed for removing non-biodegradable organics and reducing iron-sludge discharge. In MPBR, GO/PVDF membrane fabricated by chemical grafting GO nanosheets was first used for salt-tolerated PSB harvest. Compared with original PVDF membrane, GO/PVDF membrane exhibited enhanced hydrophilicity, better permeability (4.4 times) and attractive flux recover rate (94%), which was attributed to remarkable reduction in hydrophobic proteins amount of extracellular polymeric substances (EPS). Importantly, COD and NH3-N removal efficiency of MPBR with GO/PVDF membrane were kept about 95 and 98%, respectively, and average biomass productivity reached as high as 105 mg/L·d. This study provides a promising and economical way to build efficient MBR combined with new materials for high salinity hazardous wastewater treatment.

High Loaded Synthetic Hazardous Wastewater Treatment Using Lab-Scale Submerged Ceramic Membrane Bioreactor

Submerged ceramic membrane bioreactors (SCMBRs) are more efficient combinations of traditional activated hazardous sludge and new membrane separation processes in wastewater treatment. Suspended solids are separated from hazardous effluent using microfilter ceramic membranes in SCMBRs. A high loaded wastewater was treated using an SCMBR employing a homemade tubular ceramic membrane in laboratory scale. Hydraulic Retention Time (HRT) was 32 h and COD range was varied from 2000 to 5000 mg/l. COD removal was evaluated to be more than 90% after a week and the lab scale SCMBR showed desired performance for the wastewater treatment. Mixed Liquor Suspended Solid (MLSS) was increased from 2000 to 4000 mg/L during the SCMBR operation time.

Shale gas wastewater management under uncertainty

This work presents an optimization framework for evaluating different wastewater treatment/disposal options for water management during hydraulic fracturing (HF) operations. This framework takes into account both cost-effectiveness and system uncertainty. HF has enabled rapid development of shale gas resources. However, wastewater management has been one of the most contentious and widely publicized issues in shale gas production. The flowback and produced water (known as FP water) generated by HF may pose a serious risk to the surrounding environment and public health because this wastewater usually contains many toxic chemicals and high levels of total dissolved solids (TDS). Various treatment/disposal options are available for FP water management, such as underground injection, hazardous wastewater treatment plants, and/or reuse. In order to cost-effectively plan FP water management practices, including allocating FP water to different options and planning treatment facility capacity expansion, an optimization model named UO-FPW is developed in this study. The UO-FPW model can handle the uncertain information expressed in the form of fuzzy membership functions and probability density functions in the modeling parameters. The UO-FPW model is applied to a representative hypothetical case study to demonstrate its applicability in practice. The modeling results reflect the tradeoffs between economic objective (i.e., minimizing total-system cost) and system reliability (i.e., risk of violating fuzzy and/or random constraints, and meeting FP water treatment/disposal requirements). Using the developed optimization model, decision makers can make and adjust appropriate FP water management strategies through refining the values of feasibility degrees for fuzzy constraints and the probability levels for random constraints if the solutions are not satisfactory. The optimization model can be easily integrated into decision support systems for shale oil/gas lifecycle management.

Development of photocatalytic coupled zinc–iron oxide nanoparticles via solution combustion for bisphenol-A removal

Photocatalytic degradation is one of the advance oxidation processes (AOPs) that holds promising potential to solve the existing environmental issues, especially for hazardous wastewater treatment. In this study, solution combustion process is carried out to prepare coupled zinc–iron oxide nanoparticles that endowed with synergetic photocatalytic properties. The p–n junction created through the coupling of zinc oxide and iron (III) oxide is the key feature to maximize the photocatalytic activity of the resultant photocatalyst. The particle size of the synthesized coupled zinc–iron oxide photocatalysts falls in the range of 21–27 nm and the band gap has been reduced from 3.2 eV to 2.07 eV compared to the pristine zinc oxide nanoparticles. The results obtained also indicated that the increase of iron content in the coupled zinc–iron oxide could effectively reduce the band gap of the resultant photocatalyst. The prepared coupled zinc–iron oxide demonstrated promising photodegradation of bisphenol-A upon the irradiation of UV light.

Ca(II) imprinted chitosan microspheres: An effective and green adsorbent for the removal of Cu(II), Cd(II) and Pb(II) from aqueous solutions

Abstract Ca(II)–CS microspheres with uniform size and morphology were first synthesized as a green and effective absorbent for the treatment of hazardous wastewater containing heavy metal ions. The adsorption capacities for Pb(II), Cd(II) and Cu(II) reached 47.1 mg, 49.9 mg and 41.5 mg per gram of Ca(II)–CS microsphere within 30 min, respectively. The pseudo-first-order equation and Langmuir isotherm model are fit to describe the adsorption kinetics and equilibrium separately. The orders of Δ G °, Δ H ° and Δ S ° for three metal ions adsorption were in accordance with the theoretical analysis. TGA, FTIR and XPS measurements verified that Ca(II) ions played a role in tuning crosslinking degree by a weak complexation of NH 2 –Ca(II), and only amino groups were well-recognized as active sites for metal ions adsorption. An insight can be gained into the use of Ca(II)–CS microspheres for various heavy metal ions treatment in packed column.

Phenol biodegradation by mixed culture in batch reactor — Optimization of the mineral medium composition

A new phenol-degrading microbial consortium with high biodegradation activity and high tolerance to phenol was isolated from activated sludge for hazardous wastewater treatment (Boumerdès, Algeria). Biodegradation kinetics was determined by monitoring biomass and phenol consumption. Mineral medium composition and especially nitrogen source concentration, as well as culture pH, were optimized. The temperature (30°C), the stirring velocity (200 rpm) and the phenol concentration (125 mg L-1) were kept constant; while the initial pH was varied (5–9), and the mineral components were tested in the following concentration ranges: 0.25–2 g L-1 for (NH4)2SO4,1–4 g L-1 for KH2PO4 and NaH2PO4 and 0.05–0.2 g L-1 for MgSO4. All experiments were carried out at a given initial bacterial concentration, 0.08 g L-1 (based on optical density determination, 0.079). Irrespective of the culture conditions, total phenol degradation (125 mg L-1) was recorded for culture times ranging from 20.6 to 31.2 h. The optimal mineral medium concentrations were therefore, 1,3,3 and 0.1 g L-1 for (NH4)2SO4, KH2PO4, NaH2PO4 and MgSO4 respectively and the optimal pH was 8, leading to a specific growth rate of 0.64 Ir1. Higher maximum specific growth rate values were recorded during this work, if compared to those reported in the available literature, even those dealing with mixed culture. This result showed the relevance of the specific microbial consortium used.

Fundamentals and applications of the photocatalytic treatment for the removal of industrial organic pollutants and effects of operational parameters: A review

Photocatalysis process, as an environmental application, is a relatively novel subject with tremendous potential in the near future. A number of studies determine the economic viability of applying various ultraviolet advanced oxidation processes for the purpose of degradation and destroying of various pollutant solutions. The present paper reviews the treatment of hazardous wastewater bearing organic compounds and the effects of various parameters such as pH, initial concentration, mass of catalyst, wavelength, light intensity, electron acceptor, temperature, etc., with the treatment cost for different reactor type. This study investigates the effect of various types of waste-water treatment parameters and the treatment cost for various designs of photocatalytic reactors, using both solar and artificial light, have been proposed for their different types of pollutants.

Treatment of hazardous wastewater contaminated by nitrocellulose

Based on successful preliminary bench scale experimental studies for treatment of industrial wastewater contaminated by nitrocellulose, a pilot plant is constructed for results assessment. Bench scale experimental work proved 55%, 73% recovery of nitrocellulose without and with chemical addition respectively within 10 min flotation compared to 35%, 69% recovery within 2–0.5 h settling respectively. The treatment process aims the recovery of nitrocellulose through an efficient dissolved air flotation (DAF) unit. Different operating conditions have been studied for different effluent characteristics with and without flocculating agent. Nitrocellulose recovery reached 80% by flotation without chemical, which is increased to 87% using cationic polymer, but both exploring suitable pathways to solve the recovery problem.The experimental results are considered suitable basis for full scale design of the industrial treatment unit.

Treatment of Hazardous Organic and Inorganic Compounds through Aqueous-Phase Photocatalysis: A Review

Photocatalysis has been a widely studied technology since the 1970s. Many investigations have been carried out with the aim of understanding the fundamental processes and enhancing photocatalytic efficiencies especially for water, air, and soil pollution control. In this comprehensive paper, studies focused on the treatment of hazardous wastewater (bearing heavy metals and organic compounds) by photocatalysis and the effects of various parameters such as pH, light intensity, dissolved oxygen, etc., are reviewed. In addition, the design features and efficiencies of various photoreactors used for this process are discussed. Some studies on the economic analysis of photocatalytic systems are also included. It can be concluded that the photocatalysis process is suitable for the treatment of drinking water and industrial wastewater. Also, harvesting the energy of the sun for photoreactions would make it a cleaner and more cost-effective treatment method.

Catalytic Supercritical Water Oxidation of Coke Works Waste with Manganese Oxide.

Heterogeneous catalysis in supercritical water oxidation (SCWO) is a new approach to improve the reaction efficiency of the treatment of hazardous waste water. In this study, the kinetic analysis of catalytic SCWO of coke works waste with manganese oxide (MnO2) was performed to obtain fundamental data for the reactor design, as well as information about interactions affecting the reaction rate between the reaction species. The major component of the coke works waste is NH3. Catalytic SCWO of NH3 solution confirmed that MnO2 is a good catalyst for the complete oxidation of NH3. SCWO of an aqueous mixture of phenol and NH3 was examined as a model solution of the real waste. The oxidation rate of NH3 in the model solution was lower than that of an aqueous solution of NH3. The presence of NH3 in the model solution did not affect the phenol conversion, but strongly suppressed the decomposition of total organic carbon (TOC). These inhibition effects between NH3 and phenol are explainable by a Langmuir-type model, in which all corresponding species are assumed to adsorb competitively on the same catalytic site. Catalytic SCWO of diluted real waste showed a similar inhibition effect especially with shorter contact times of less than 0.5s. However, very high conversions of both NH3 and TOC were achieved within 2s of contact time at 500°C. These experimental results suggest that catalytic SCWO is a promising technique for the complete decomposition of coke works waste.

Full scale treatment of hazardous wastewater through thermal reduction

An attempt has been made to present the data relating to full scale application of evaporation‐incineration technology for containment of wastewater emanating from H‐acid (mono sodium salt of 1 amino‐8‐hydroxynapthalene 3,6‐disulphonic acid) production with recourse to zero wastewater discharge. The wastewater is acidic with high concentrations of COD and total dissolved salts and BOD/COD ratio of 0.11. NOx, SOx, SPM and CO from stack emissions are within the standards stipulated by the statutory bodies.

BIODEGRADATION PROCESS ANALYSIS BY ULTRAFILTRATION

Detailed analysis of biological processes for hazardous waste-water treatment presents extreme difficulty. Complexity of organic and inorganic solute mixtures in solution prohibits GC-MS analysis. Gross parameters must be used to monitor treatment process performance. Ultrafiltration, coupled with gross parameter estimation, provides enhanced definition of treatment. Results, employed to monitor in-situ biodegradation of a hazardous landfill leachate, are discussed.