Fixed-bed Column Tests Research Articles

Nanoparticles for treatment of cadmium-contaminated cocoa-growing soils and beans: Performance on metal immobilization and removal.

Some areas of tropical soils where cocoa grows contain high cadmium (Cd) concentrations. The cocoa plant's need for nutrition causes the reticular system to uptake the toxic metal, translocate it, and accumulate it in roots, stems, and other edible parts such as cocoa beans and shells, threatening the health of cocoa consumers. To cope with this difficulty, different treatments have been applied to cadmium-contaminated soils, but they showed limited success. In this study, we prepared multicomponent nanoparticles (MCNPs) to treat cocoa soils in fixed-bed columns and field tests. Also, MCNPs were mixed with two varieties of cocoa beans, CNN51 and Fino de Aromain, during the fermentation, aiming to capture the cadmium. Our field investigations began by collecting soil samples from three Ecuadorian cocoa-producing farms to determine their physicochemical properties, cadmium, and iron contents. A few weeks later, a home-built prototype was installed in a cocoa plantation to fabricate the nanomaterials using commercial-grade chemicals and rainwater. Scanning Electron Microscope (SEM) images showed MCNPs with an average size of 65.21 nm and the formation of chain-like aggregates. In contrast, MCNPs size was 76.6 nm, measured with Dispersed Light Scattering (DLS). The chemical composition of MCNPs was 90.7% Fe0 and 1.81% sulfur (S), analyzed by energy dispersal X-ray (EDX) and confirmed by X-ray diffraction (XRD) spectrometer measurements. Regarding the treatments, for the fixed-bed column tests, 0.28-1.08 L/kg was dosed into the soil, while for field treatments, 250, 500, and 835 mL/min MCNPs were injected in soil areas of 5 m2 surrounding each cocoa tree (0.5-4.5 mg MCNPs/kg soil) at depths between 0 and 5 cm. Test results revealed that the procedure applied in the field did not reproduce the metal’s immobilization (∼22%) as in the fixed-bed columns (∼80%). Moreover, cadmium removal was ∼ 20% and ∼75% after treating CCN51 and Fino de Aroma cocoa beans with 0.112 kg MCNPs/kg in the fermentation on-site and 0.034 kg MCNPs/kg in the laboratory. In this study, the size and chain-like aggregates of MCNPs notably influenced the field treatments as they precluded the filtration of MCNPs downwards. However, immobilizing cadmium could be more effective in soils with higher concentrations of the metal and multicomponent nanoparticles of smaller size, expanding our research scope and offering a practical solution to pollution issues in cocoa-growing regions.

Highly efficient arsenate removal using novel La-GO/B granules: Performance evaluation and mechanistic exploration in simulated real water system

This study addresses the primary challenge in arsenate [As(V)] remediation: developing an adsorbent that offers abundant active sites, high affinity, and capacity for As(V) removal while ensuring contaminant levels remain within safe limits. It introduces lanthanum oxide-modified graphene oxide/bentonite (La-GO/B) granules, synthesized in a porous sodium alginate matrix, which exhibit efficient As(V) removal. The granules maintain consistent performance across a pH range of 3–6 and are unaffected by competing ions, demonstrating robustness in complex water environments. With a Langmuir adsorption capacity of 138.45 mg/g at pH 6.0, they retain substantial capacity after five adsorption-desorption cycles. X-ray photoelectron spectroscopy and experimental analysis confirm inner-sphere complexation between As(V) and lanthanum as the main adsorption mechanism. The granules release no detectable lanthanum or by-products, ensuring safety and stability. In fixed-bed column tests, they treat up to 3,800 bed volumes of water, maintaining arsenate concentrations below WHO permissible limits, establishing La-GO/B granules as a promising arsenate adsorbent for water treatment applications.

Evaluation of engineered binderless alumina – titania beads for fluoride removal from impaired water resources

Groundwater is often contaminated with various species, with fluoride concentrations being of particular concern. Numerous studies have used adsorbents for fluoride uptake, but most are tested only as powders and not commercially acceptable engineered shapes. Therefore, it was necessary to evaluate the performance of the newly developed Al2O3/TiO2 sorbents in their beaded form to assess their efficacy in comparison to activated alumina granules. Binderless sorbent beads were self-bound with the alumina and titania phases present. The fluoride exchange kinetics of Al2O3/TiO2 beads were comparable to the powdered form. Moreover, the Al2O3/TiO2 beads had higher fluoride loading than commercially available alumina (0.17 meq/g compared to 0.13 meq/g). The Al2O3/TiO2 beads also removed: barium, calcium, lithium, magnesium, manganese, potassium, silica, and strontium from groundwater. In fixed bed column tests, the beads-maintained fluoride within acceptable limits for 42 bed volumes, which substantially outperformed activated alumina (2.5 bed volumes). This study demonstrated that Al2O3/TiO2 beads outperformed commercially available activated alumina materials. Notably, transforming the materials into beaded forms significantly improved their suitability for fluoride removal in industrially relevant fixed-bed column environments. Future studies should focus on enhancing material binding properties to increase crush strength and attrition resistance. A deeper knowledge of regeneration strategies may also facilitate cost reduction.

Acyl chloride-mediated synthesis of rhodanine-modified UiO-66 for high-efficiency silver recovery

Silver (Ag) recovery is essential for ecological protection, human health and economic benefits. Effective capture of Ag(I) from wastewater is still challenging due to insufficient accessible sites of adsorbents. Herein, an acyl chloride-mediated strategy is developed to synthesize rhodanine (Rd) modified UiO-66 derivatives for Ag(I) adsorption. Benefitting from the high grafting density of Rd, the optimal Rd-modified UiO-66-NH2 (UiO-66-NH2@20Rd) features an ultra-high uptake capacity (maximum capacity of 923.9 mg·g−1) and selectivity (maximum selectivity coefficient of 1665.52) for Ag(I). Almost 90 % of Ag(I) could be captured in one minute over UiO-66-NH2@20Rd and maintained a removal rate of 98.9 % even after six cycles. Moreover, a fixed-bed column test demonstrates that approximately 21,780 bed volumes of Ag(I) simulated wastewater can be effectively treated, indicating great promise for practical application. Mechanism investigation illustrates that outstanding performance can be attributed to the synergistic effect of Ag(I) adsorption and reduction on dense rhodanine sites. This study highlights that such a general strategy can provide a valuable avenue toward various functional adsorption materials.

A robust self-regenerating graphene-based adsorbent for pharmaceutical removal in various water environments

The presence of active pharmaceutical ingredients (APIs) in wastewater effluents and natural aquatic systems threatens ecological and human health. While activated carbon-based adsorbents, such as GAC and PAC, are widely used for API removal, they exhibit certain deficiencies, including reduced performance due to the presence of natural organic macromolecules (NOMs) and high regeneration costs. There is growing demand for a robust, stable, and self-regenerative adsorbent designed for API removal in various environments. In this study, we synthesized a self-generating metal oxide nano-composite (S-MGC) containing titanium dioxide (TiO2) and silicon dioxide (SiO2) combined with 3D graphene oxide (GO) to adsorb APIs and undergo regeneration via light illumination. We determined optimal TiO2:SiO2:GO compositions for the S-MGCs through experiments using a model contaminant, methylene blue. The physical and chemical properties of S-MGCs were characterized, and their adsorption and photodegradation capabilities were studied using five model APIs, including sulfamethoxazole, carbamazepine, ketoprofen, valsartan, and diclofenac, both in single-component and multi-component mixtures. In the absence of TiO2/SiO2, 3D graphene oxide (CGB) displayed better adsorption performance compared to GAC, and S-MGCs further improve CGB's adsorption capacity. This performance remained consistent in two complex water environments: aqueous solutions at varying NOM levels and artificial urine. TiO2 supported on the GO surface exhibits similar photocatalytic activity to suspended TiO2. In a continuous fixed-bed column test, S-MGCs demonstrated robust API adsorption performance that is maintained in the presence of NOM or urine, and can be regenerated through multiple cycles of adsorption and light illumination.

Characterization and Performance of Peanut Shells in Caffeine and Triclosan Removal in Batch and Fixed-Bed Column Tests.

Peanut shells' adsorption performance in caffeine and triclosan removal was studied. Peanut shells were analyzed for their chemical composition, morphology, and surface functional groups. Batch adsorption and fixed-bed column experiments were carried out with solutions containing 30 mg/L of caffeine and triclosan. The parameters examined included peanut shell particle size (120-150, 300-600, and 800-2000 µm), adsorbent dose (0.02-60 g/L), contact time (up to 180 min), bed height (4-8 cm), and hydraulic loading rate (2.0 and 4.0 m3/m2-day). After determining the optimal adsorption conditions, kinetics, isotherm, and breakthrough curve models were applied to analyze the experimental data. Peanut shells showed an irregular surface and consisted mainly of polysaccharides (around 70% lignin, cellulose, and hemicellulose), with a specific surface area of 1.7 m2/g and a pore volume of 0.005 cm3/g. The highest removal efficiencies for caffeine (85.6 ± 1.4%) and triclosan (89.3 ± 1.5%) were achieved using the smallest particles and 10.0 and 0.1 g/L doses over 180 and 45 min, respectively. Triclosan showed easier removal compared to caffeine due to its higher lipophilic character. The pseudo-second-order kinetics model provided the best fit with the experimental data, suggesting a chemisorption process between caffeine/triclosan and the adsorbent. Equilibrium data were well-described by the Sips model, with maximum adsorption capacities of 3.3 mg/g and 289.3 mg/g for caffeine and triclosan, respectively. In fixed-bed column adsorption tests, particle size significantly influenced efficiency and hydraulic behavior, with 120-150 µm particles exhibiting the highest adsorption capacity for caffeine (0.72 mg/g) and triclosan (143.44 mg/g), albeit with clogging issues. The experimental data also showed good agreement with the Bohart-Adams, Thomas, and Yoon-Nelson models. Therefore, the findings of this study highlight not only the effective capability of peanut shells to remove caffeine and triclosan but also their versatility as a promising option for water treatment and sanitation applications in different contexts.

Ultra-high selective removal of Congo red and Ciprofloxacin using unusual LDO modified biochar: Influence of emerging pollutants and application attempts

The porous biochar materials serve as effective adsorbents in water treatment. In this study, layered-double-hydroxide (LDH)(MgAl) was dispersed onto waste poplar powder through the co-precipitation method, followed by pyrolysis to prepare layered-double-oxides (LDO)/poplar carbon (CL-800) for ultra-high adsorption of Congo red (CR) and Ciprofloxacin (CIP). The CL-800 adsorbent possessed a well-developed layered porous structure that provides numerous adsorption sites and transport channels for dyes and antibiotics. Notably, CL-800 exhibited a significantly elevated level of selectivity and adsorption capacity towards CR and CIP reaching 93.0, 84.7 % and 4841.2, 744.0 mg/g, respectively. Various factors were considered to investigate the influence on CR and CIP adsorption, such as ion types, microplastics, and perfluorooctanoic acid. The adsorption capacity in complex water systems were also explored where CL-800 presented excellent removal efficiencies for CR (99.0 %) and CIP (89.6 %) in simulated wastewater along with good repeatability. Fixed-bed column tests also confirmed its potential as an effective adsorbent for wastewater purification due to continuous adsorption properties towards CR and CIP over time. Finally, the interaction mechanisms for CR/CIP adsorption processes onto CL-800 were possibly determined via various advanced techniques. This study provides new perspectives for providing a potential low-cost efficient adsorbent for organic wastewater treatment.

Disclosing the intrinsic nature of efficient removal of antibiotics in N/S dual-doped porous carbon-based materials: The manipulation of internal electric field

N/S co-doping has emerged as a prevailing strategy for carbon-based adsorbents to facilitate the antibiotic removal efficiency. Nevertheless, the underlying interplay among N, S, and their adjacent vacancy defects remains overlooked. Herein, we present a novel in situ strategy for fabricating pyridinic-N dominated and S dual-doped porous carbon adsorbent with rich vacancy defects (VNSC). The experimental results revealed that N (acting as the electron donor) and S (acting as the electron acceptor) form an internal electric field (IEF), with a stronger IEF generated between pyridinic-N and S, while their adjacent vacancy defects activate carbon π electrons, thus enhancing the charge transfer of the IEF. Density functional theory (DFT) calculations further demonstrated that the rich charge transfer in the IEF facilitated the π-π electron donor-acceptor (EDA) interaction between VNSC and tetracycline (TC) as well as norfloxacin (NOR), and thus is the key to adsorption performance of VNSC. Consequently, VNSC exhibited high adsorption capacities toward TC (573.1 mg g−1) and NOR (517.0 mg g−1), and its potential for environmental applications was demonstrated by interference, environmentally relevant concentrations, fixed-bed column, and regeneration tests. This work discloses the natures of adsorption capacity for N/S dual-doped carbon-based materials for antibiotics.

Characteristics of Zinc Adsorption onto Biochars Derived from Different Feedstocks

Human activities such as the discharge of urban sewage, garbage, and industrial waste have seriously affected the quality of groundwater sources for human consumption. The potential for using biochar as a reactive medium in a permeable reactive barrier (PRB) was explored for Zn-contaminated groundwater treatment in this study. Four different types of biochar produced from wood, coconut shell, rice straw, and fruit shell were used. The production temperature of these biochars were 600 °C, 550 °C, 500 °C, and 500 °C, respectively. The samples were coded with the initials of the biochar source and the production temperature as WD600, CS550, RS500, and FS500. The results of various batch adsorption studies show that equilibrium solution pH has a great effect on the maximum adsorption capacity in the pH range of 2–7. The adsorption of Zn on biochars follows the Freundlich model and fits well with the pseudo-second-order model. The fixed-bed column test data were well fitted to the Dose–Response model. The adsorption capacities of WD600, CS550, RS500, and FS500 were 24.91, 15.87, 9.25, and 46.71 mg/g, respectively. The removal rate of FS500 can reach a maximum of 98.87%. FS500 is considered to be a potential reaction medium for treating Zn-contaminated groundwater in a PRB system. This work provides a new option for converting biomass waste into an adsorbent for zinc in wastewater. The results of this study are expected to provide a solid theoretical basis for the further application of biochar in groundwater pollution remediation.

Selective capture of palladium from acid wastewater by thiazole-modified activated carbon: Performance and mechanism

As a kind of scarce metal, palladium is widely used in many chemical industries. It essential to recover palladium from secondary resources, especially acidic media, owing to high content of palladium in secondary wastes and widespread extraction of palladium via strong acids. Chemically modified carbon materials not only have the advantage of activated carbon but also achieve the precise removal of specific pollutants, which is a kind of adsorption material with broad application prospects. In this direction, we report a solid carbon material named AT-C, which is obtained by one-step synthesis of 2-aminothiazoles grafted to the carbon surface by amidation. The present adsorbent delivers a high palladium adsorption capacity of 178.9 mg g−1, and desirable thermal and chemical stability. The uniform presence of abundant sulfur atoms and CO in the porous network enables AT-C to achieve selective absorption and rapid adsorption kinetics of Pd2+ in the complex water mixture containing many competing ions in the acidic pH range. For the strongly acidic leachates of catalysts, AT-C exhibits outstanding stability in cyclic experiments. Meanwhile, the fixed-bed column test indicates that 1076 bed volumes of the feeding streams can be effectively treated. In addition, AT-C exhibits superior adsorption selectivity, and the recovery efficiency of Pd2+ in actual industrial wastewater is 96.6%. This work realizes an efficient, rapid, and selective removal of palladium under acidic conditions, and provides a reference for complex industrial water treatment and resource recovery of precious metals.

Novel Phytic Acid-Based Supramolecular Material for Uranium Removal from Highly Acidic Media: Synthesis, Performance, and Mechanistic Insights

The efficient adsorption and removal of U(VI) from nuclear wastewater is fetching growing interest due to its importance for the ecological environment and human health. In this study, we report a facile ionic self-assembly method to synthesize a phytic acid-based material denoted PE-x using phytic acid and ethylenediamine. PE-x was applied to remove U(VI) from a highly acidic aqueous solution with pH = 1.0. In batch adsorption experiments, PE-x showed fast removal kinetics for U(VI) with an equilibrium time around 10 min, excellent selectivity for An-Ln and U(VI) with a maximum selectivity of 97.8% and 76.2%, and a remarkable maximum adsorption capacity of 689.7 mg/g toward U(VI). Additionally, PE-x exhibited a considerable adsorption capacity of 282.6 mg/g in the fixed bed column test. The adsorption mechanism was investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results indicate a unique mechanism based on the reconstruction of the self-assembly framework involving U(VI) building blocks driven by positively charged species exchange. This study provides new insights and strategies for the design of enhanced uranium adsorbents under highly acidic conditions and extends the potential practical application of phytic acid for uranium capture from radioactive wastewater.

Biochars-FexPCu hybrides deriving from solid waste and waste acids for elimination of refractory organic pollutants from pharmaceutical wastewater

A novel Fe based nanocomposite was fabricated by using solid waste, waste acids, iron ores and copper salts as raw materials. The composites were composed of biochars, iron phosphides, iron carbide and Cu (BC-FexPCu), and applied as pre-treating materials to degrade 3,4,5,6-tetrachloropicolinic acid (TCPA) from saline water. In a wide pH (4–10), temperature (25–65 °C) and salinity (0–25 g L-1 of NaCl) range, TCPA could be eliminated completely within 240 min from saline water with the corresponding mineralization efficiency ranged in 65.4–85.9 %. High concentration of ·OH, O2–· and 1O2 was continuously detected in BC-FexPCu reaction solution owing to efficient activation of dissolved oxygen by BC-FexPCu. The BC-FexPCu showed good performance in pretreating wastewater from a chloropyridine herbicide production plant. In batch experiment, about 60 % of total organic carbon (TOC) was removed from wastewater within 180 min without the requirement of H2O2. In the fixed bed column test, the elimination efficiency of TOC maintained 30 % with the help of discontinuous aeration. The recycle test suggested that the long-lasting activity of BC-FexPCu could be achieved when the targets were degraded only by reactive oxygen species in the system. Compared to zero-valent iron and commercial Fe/C materials, the advantages of BC-FexPCu include good stability, cost-effectiveness, and less chemical requirements.

Polymer-microsphere coated with MoS2 nanoflowers for the removal of Pb(II) from water: Polydopamine-mediated MoS2 assembly and efficient Pb(II) adsorption

The engineering of macroscopic architectures by loading MoS2 nanosheets onto larger framework materials is an efficient strategy to overcome the limitations preventing the application of nanosized MoS2-based adsorbents for Pb(II) removal. However, the large-scale utilization of these nanocomposites still faces several challenges as a result of their poor stability, slow adsorption kinetics, and low MoS2 utilization. Herein, a practical and efficient nanocomposite (MoS2/PDA/MPS) was prepared by coating MoS2 nanoflowers onto micron-sized polystyrene beads (MPS) via the construction of a strong adhesive polydopamine (PDA) interlayer. The PDA interface can adhere to the MPS surface and immobilize the MoS2 nanopartices, thus facilitating the application of MoS2/PDA/MPS in flow-through systems. Further, the flower-like structure of the MoS2 on the outer surface of the host exposes active sites and facilitates mass transfer compared to those of traditional nanocomposites. Meanwhile, the R-SO3- groups of MPS can enhance permeation and preconcentrate the Pb(II) ions via the Donnan membrane effect, resulting in improved adsorption kinetics and capacity. Batch adsorption experiments revealed that MoS2/PDA/MPS shows fast adsorption kinetics (<45 min), exceptional adsorption capacity (371.7 mg/g, calculated from the Langmuir model at 298 K), and high adsorption selectivity for Pb(II) uptake. The excellent stabilities and reusability of the nanocomposite were tested over 10 adsorption–desorption cycles. In addition, a considerable working capacity (approximately 2000 BV) in synthetic wastewater was observed in fixed-bed column tests, and the used adsorbent could be readily regenerated with a binary NaCl–EDTANa2 solution for reuse without significant capacity loss. Thus, MoS2/PDA/MPS has great applications for the remediation of lead-containing wastewater, and our findings provide new insights into the preparation of efficient MoS2-based adsorbents having practical applications.

Study of Adsorption Efficiency of Lignite, Biochar, and Polymeric Nanofibers for Veterinary Drugs in WWTP Effluent Water

The increased consumption, overuse, and subsequent difficult removal of pharmaceuticals using conventional processes lead to their rising prevalence in the environment. Adsorption belongs to the most efficient approaches to pharmaceuticals’ removal from wastewater. This study provides insight into the sorption properties of biochar, lignite, and polyamide nanofibers (PA-nanofibers) for sulfamethoxazole, trimethoprim, clarithromycin, azithromycin, and amoxicillin in ultrapure and wastewater treatment plant (WWTP) effluent water. The negative effect of WWTP effluent water was reflected in a reduction of the sorption capacity of biochar by 6.31–72.15%, 25.58–98.55% for lignite, and 4.21–67.71% for PA-nanofibers. Simultaneously, this study investigates the impact of the experimental setup. The sorption capacities were recorded in the range from 0.65 to 2.84 mg g−1 for biochar, 0.04 to 75.73 μg·g−1 for lignite, and 0.53 to 30.54 μg·g−1 for PA-nanofibers during the fixed-bed column tests with WWTP effluent water. Based on the results, biochar appears to be a suitable sorbent for selected pharmaceuticals in field conditions with running water. Lignite and PA represent complementary treatment technology or can act as a carrier for microbial degraders. Performed batch tests with ultrapure and WWTP effluent water and subsequent column tests highlighted the importance of conducting tests with the appropriate matrix and experimental setup to gain a realistic insight into the behavior of the sorbents under environmentally relevant conditions.Graphical

Fabrication of 1-octane sulphonic acid modified nanoporous graphene with tuned hydrophilicity for decontamination of industrial wastewater from organic and inorganic contaminants.

This research work is based on the fabrication of a graphene oxide-based composite (GOBC) to remove the maximum number of contaminants from different industrial effluents. The GO was first intercalated with 1-octanesulphonic acid sodium salt and subjected to microwave irradiation to produce GOBC. Fixed-bed column tests and Jar-tests were performed for removal of the most harmful endocrine disrupting compounds (EDCs) such as bisphenol A, bisphenol S, endosulphan, beta-estradiol, dyes (methylene blue and violate) and toxic metal ions such as Pb2+, Li+, Ni2+, Co2+, Cr6+, Zn2+, Cd2+, Hg2+, Cu2+, and As5+via adsorption. The prepared material was thoroughly characterized for its unique functional and structural properties. The results obtained from Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller, scanning electron microscopy, Raman spectroscopy, water contact angle and X-ray diffraction analysis confirmed the successful preparation of GOBC using the proposed intercalation/microwave method. The water contact angle results showed decreased hydrophilicity of GOBC as compared to GO as the contact angle of GOBC (77.75°) was higher than that of GO (53.98°). The effects of main column parameters such as bed height, initial analyte concentration and solution flow rate were investigated. The results revealed that shorter breakthrough time, and high adsorption capacity were obtained at high flow rates of 1 mL min-1, while longer breakthrough time and lower adsorption capacity were obtained at lower flow rates of 0.5 mL min-1. The effect of bed depth on the breakthrough curve of analyte adsorption was a steep breakthrough curve; or a shorter breakthrough time occurring at lower bed height. The adsorption data obeyed the Yoon-Nelson and Thomas models very well. The adsorption capacity for BPA, BPS, endosulphan, beta-estradiol, methylene blue and violate was found to be 307, 305, 260, 290, 230 and 195 mg g-1, respectively. The adsorption capacity of GOBC for toxic metal ions such as Pb2+, Li+, Ni2+, Co2+, Cr6+, Zn2+, Cd2+, Hg2+, Cu2+, and As5+ was found to be 156, 136, 126, 124, 118, 114, 82, 82, 72 and 72 mg g-1, respectively with excellent kinetics. The adsorption data obtained using Jar-tests revealed that GOBC obeys a Langmuir isotherm and a pseudo second order kinetics model. The analysis of industrial wastewater samples showed good removal efficiency of GOBC.

Escherichia coli inactivation in water by sulfate radical-based oxidation process using FeCl3-activated biochar/persulfate system

Pathogenic microbes in water present great risks to environments, water resources, and human health. In the present study, for the first time, a FeCl3-activated bermudagrass-derived biochar (FA-BC) was applied to activate persulfate (PS) for E. coli inactivation. The PS activation was ascribed to the presence of Fe0 and Fe3O4 on the surface of FA-BC, and SO4·− radicals were proved to be the main role for E. coli inactivation using FA-BC activated PS system (FA-BC/PS). Decreasing the pH (5–9) and increasing the PS concentration (50–300 mg/L), reaction temperature (20–50 °C), and FA-BC dosage (100–500 mg/L) resulted in the enhancement of disinfection efficiency of E. coli using FA-BC/PS. 6.21 log reductions of E. coli were achieved within 20 min under the optimal conditions (500 mg/L FA-BC, 200 mg/L PS, pH 7, and 20 °C with 107 CFU/mL E. coli in DI water). The FA-BC/PS effectively eliminated various initial concentrations of E. coli (105–108 CFU/mL). The E. coli inactivation rate decreased from 0.1426 min−1 to 0.0883, 0.1268 min−1, and 0.1093 min−1 with the presence of 10 mg/L humic acid, 100 mg/L Cl−, and 100 mg/L HCO3−, respectively. In addition, after three cycles of disinfection tests using FA-BC/PS, the E. coli inactivation rate only slightly decreased from 0.1426 to 0.1288 min−1. The FA-BC/PS also effectively removed the E. coli in real stormwater with a 99.2 % inactivation efficiency within 180 min. The FA-BC/PS in fixed-bed column tests revealed the continuous and high inactivation of E. coli in water. Increasing the FA-BC amount (1.5 %–5 %) and PS concentration (50–200 mg/L) and decreasing the flow rate (2–4 mL/min) caused the lower E. coli concentration in effluent. Therefore, the FA-BC/PS can be considered as a promising and efficient technique for water disinfection.

Selective and efficient removal of As(V) and As(III) from water by resin-based hydrated iron oxide

Arsenic pollution in natural water is a worldwide problem. In this work, a resin-based hydrated iron oxide (D303-HFO) adsorbent was designed to remove arsenate (As(V)) and arsenite (As(III)) in the groundwater. The structure and morphology of the D303-HFO adsorbent were characterized by FTIR, XRD, SEM and TEM tests. The specific surface area, pore volume and pore size increased with the incorporation of HFO nanoparticles in the resin. In addition, the effects of pH and coexisting ions on the arsenic removal efficiency were investigated. Results indicated that the D303-HFO had efficient removal performance for arsenic in the pH range of 3–9 and showed high selectivity for As(V) and As(III) under the influence of competitive ions. The adsorption kinetics study confirmed that the adsorption process was dominated by chemisorption, and the adsorption isotherms of As(V) and As(III) by D303-HFO fitted the Langmuir model. Thermodynamic parameters indicated that the adsorption reaction was spontaneous and exothermic. Moreover, the regeneration and stability experiment indicated that the D303-HFO adsorbent was super reusable after five consecutive cycles and could be put into service stably and permanently. The fixed-bed column test showed that the water sample containing As(V) and As(III) was treated with a volume of 900BV and 1100BV, respectively. After the treatment, the effluent concentration reached the drinking water standard stipulated by WHO.

Removal of Mn(II) from Acidic Wastewater on the Red Mud– Loess Mixture: Fixed–Bed Column Tests

In this study, the purification effect of red mud–loess mixture (RM–L) as a reactive medium in a permeable reactive barrier (PRB) for groundwater contaminated by acidic wastewater (AW) containing Mn(II) was explored considering removal capacity and pH value, and the safety of Mn(II) on RM–L after purification was evaluated. The breakthrough parameters of the Mn(II) were determined and the purifying performances of RM–L toward AW were evaluated by fixed-bed column tests at various initial concentrations of Mn(II), flow rates, and packing heights. The speciation of Mn(II) loaded on the RM–L was evaluated by the Tessier method. Results show the RM–L with a removal capacity of 17.30 mg·g−1 at 100 mg·L−1 initial concentration, 1 mL·min−1 flow rate and 7 cm packing height. The reduction in initial concentration and flow rate and the increase in packing height improve the total removal percentage of Mn(II) and the removal capacity of the RM–L. Moreover, the RM–L has a long-term effective acid buffer capacity for AW containing Mn(II), ensuring the pH values of effluent could be maintained at a neutral value. Furthermore, the Mn(II) could be loaded on the RM–L after the purification in stable forms that are dominated by the iron-manganese oxidate form.

Designing a 3D-MoS2 nanocomposite based on the Donnan membrane effect for superselective Pb(II) removal from water

Developing more practical and efficient adsorbents is highly desirable for lead purification. Although MoS2 nanosheets have an excellent affinity for lead ions, their narrow layer spacing and ultrafine size hinder their scaled-up application. Herein, a novel type of 3D nanocomposite, W-MoS2@SCA, was synthesized by confining MoS2 nanoparticles with widened interlayer spacing (W-MoS2) in the networking pores of sulfonated cellulose aerogel (SCA). The excellent hydraulic property provided by the porous host overcomes the shortcomings of MoS2 nanomaterials and makes the composite have a satisfactory treatment effect in the flow-through system. Combined with the Donnan membrane effect produced by the positively charged sulfonic group of the host and the excellent affinity of MoS2 for lead ions, W-MoS2@SCA exhibits rapid adsorption kinetics (75 min to reach adsorption equilibrium) and superselectivity for Pb2+ removal. The distribution coefficient for Pb2+ is up to 1.01 × 105 mL/g even in complex wastewater mixed with multiple metal ions. Fixed-bed column tests indicate that an efficient application is achieved with a treatment capacity of 9000 kg wastewater/kg sorbent based on the wastewater discharges of China. Specifically, residual Pb2+ in the first 7000 kg effluent was virtually undetectable. In addition, the exhausted sorbent could be easily regenerated by the NaCl-Na2EDTA binary solution and maintained good reusability without significant capacity loss after 10 adsorption–desorption cycles. The results demonstrate that W-MoS2@SCA has great potential for use in deep purification for lead sequestration in advanced wastewater treatment.

Adsorption of Heavy Metals from Small-Scale Gold Processing in Baguio Mining District, Philippines

Small-scale mining in the Philippines lacks research and technologies for the application of an inexpensive and environmentally sound treatment of its wastewaters. Hence, laboratory-scale fixed-bed column tests were carried out to test and evaluate the sorbent adsorption performance of the Philippine Natural Bentonite (PNB) and the Philippine Natural Zeolite (PNZ) against the heavy metals present in the ball mill facilities within the Baguio Mining District. Results showed that removal percentages of PNB and PNZ in terms of lead (Pb) concentrations are 50.43% and 26.90%, respectively. Moreover, the dynamic uptake capacity and maximum adsorption capacity values of PNB showed greater values than PNZ and the sorption models, Bohart-Adams, Wolborska, Thomas, and Yoon-Nelson models, displayed good fit for the breakthrough curves. Furthermore, varying the flow rate and bed height manifested that an increase in flow rate yields a lesser saturation time while the rise in bed height increases uptake capacity, saturation time, and removal percentage of the system. Regarding the cost efficiencies of the sorbents, the study revealed that PNB is more cost-efficient than PNZ since only 1.13 Philippine pesos of PNB is required to remove a gram of Pb compared to PNZ, which costs 3.5 pesos. Therefore, this research concluded that PNB could be a better sorbent of Pb in terms of removal percentage and cost-efficiency. The study recommends further regeneration studies for the reusability of the sorbents after exhaustion and hopes that this research will be a springboard for further environmental studies.