Synthetic Effluent Research Articles

PHYTOREMEDIATION AND EXTRACTION OF COLLOIDAL CONTAMINANTS FROM MINE EFFLUENTS THROUGH LEGUME PLANTS

The bioaccumulation and environmental toxicity of colloidal contaminants have always been the focus of extensive research. Here we report efficient extraction of iron oxide colloidal contaminants from mine drainage effluents by phytoremediation with legume plants. The smallest fine particles with size less than 10 nm exhibit two wide absorption peaks at 350 and 495 nm, respectively. They have good dispersibility in aqueous environment and are highly resistant to removing or purification by any gravitational settings. The ultra-small nanosized particles (with average diameter 2-3 nm) can be bioaccumulated into the roots of soybean sprouts and might cause physiological stress and inhibition of the germination process. All experimental data found delayed growth, as well as decreased biomass production, which was observed in both the stem and root system of treated sprouts. Nevertheless, the immersed in mine effluent plants showed some resistance to the colloid toxicity. The light microscopic analysis also revealed the occurrence of more intensive symbiosis between the root tubers and the rhizosphere microbial communities in the case of phytorenmediation. The absorbance spectroscopic measurement demonstrated about 90 % efficient colloidal removement from the suspension within 10 days treatment. The atomic absorption spectroscopy analysis of mineralised sprouts cultured in synthetic mine effluents found that the highest concentration of accumulated iron in the legume plants was 258,02 ± 23,48 mg/100 g, which was achieved in suspension of 25 mM FeSO4. The presented report enables potential practical application of legume plants in the circumneutral passive treatment systems for remediation of mine effluents.

The effects of carbon nitrogen ratio and salinity on the treatment of swine digestion effluent simultaneously producing bioenergy by microalgae biofilm

In order to remove high concentrations of ammonia nitrogen (NH4+-N) and refractory sulfamethazine (SM2) from swine digestion effluent, different carbon/nitrogen (C/N) ratios and salinity were used to determine the effects of pollutants removal in the microalgae biofilm system. Microalgae biofilm treatment under optimal environmental conditions in synthetic swine digestion effluent were C/N ratio of 20 and salinity of 140 mM. In order to make the actual swine digestion effluent discharge up to the standard, three different two-cycle treatments (suspended microalgae, microalgae biofilm, microalgae biofilm under the optimal conditions) were studied. The results showed that after two-cycle treatment with microalgae biofilm under the optimal conditions, the actual swine digestion effluent levels of total nitrogen (TN), NH4+-N, total phosphorus (TP), chemical oxygen demand (COD), SM2 were 22.65, 9.32, 4.11, 367.28, and 0.99 mg L−1, respectively, which could satisfy the discharge standards for livestock and poultry wastewater in China. At the same time, first-order kinetic simulation equations suggested a degradation half-life of 4.85 d for SM2 under optimal conditions in microalgae biofilm, and microbial community analysis indicated that the dominant genus was Halomonas. Furthermore, 35.66% of lipid, 32.56% of protein and 18.44% of polysaccharides were harvested after two-cycle in microalgae biofilm treatment under optimal environmental conditions. These results indicated that the regulation of C/N and salinity in microalgae biofilm for the treatment of swine digestion effluent was a high-efficiency strategy to simultaneously achieve wastewater treatment and bioenergy production.

A mixed-charged polyelectrolyte complex nanofiltration membrane for mitigating scaling during high-recovery wastewater effluent desalination

The high salinity of wastewater effluent restricts its sustainable use for irrigation. Nanofiltration (NF) membranes can desalinate effluent. However, the applicability of polyamide NF membranes for effluent desalination is limited by high scaling, particularly calcium phosphate, and the permeate's high sodium adsorption ratio (SAR). This research presents a simple method to fabricate a mixed-charged polyelectrolyte complex NF (PECNF) membrane to overcome these challenges. The performance of the PECNF membranes was optimized by varying the polyanion-polycation ratio and total polyelectrolytes mass load and utilizing crosslinking. The resultant PECNF membrane exhibited 7.2 LMH/bar permeance and similar rejection of different types of ions. Scaling experiments using synthetic and real effluents mimicking 80 % recovery revealed that the PECNF membrane has lower scalant forming ions rejection and comparable TDS rejection (35 %) than commercial polyamide NF membrane (NF 270). Consequently, the scaling propensity of the PECNF membrane, evaluated by permeate flux reduction (∼33 %) after 50 h of filtration, was lower than that of the NF 270 membrane (∼70 % reduction). Additionally, the SAR value of the PECNF membrane's permeate was substantially lower. The PECNF membrane's stability, permeate quality, and anti-scaling properties make it a promising alternative to polyamide membranes for high-recovery effluent desalination.

Surfactant-supported organoclay for removal of anionic food dyes in batch and column modes: adsorption characteristics and mechanism study

This study aimed to create CTAB-modified bentonite organoclay (Bt@CTAB) by mixing the naturally occurring mineral bentonite (Bt) with the cationic surfactant cetyltrimethylammonium bromide (CTAB). Elemental analysis, N2 adsorption–desorption isotherm, scanning electron microscopy (SEM), FTIR spectroscopy, XRD, and thermogravimetric (TGA) analysis have been employed to analyze both the unmodified Bt and the Bt@CTAB organoclay. The dye sorption onto Bt@CTAB organoclay was investigated in the batch and column modes using aqueous solutions of anionic food dyes, viz., Sunset yellow FCF (E110), Azorubine (E122), and Ponceau 4R (E124) (individually or in a mixture). Experimental variables affecting the adsorption process, such as initial dye concentration, contact time, temperature, pH, and adsorbent dose, are evaluated. From the kinetic investigations, the adsorption of E110, E122, and E124 dyes well matched the pseudo-second-order kinetic model. E110 and E122 dyes adsorption onto Bt@CTAB attained equilibrium in 120 min while attained in 240 min for E124. The investigated food dyes were expected to achieve maximum adsorption efficiencies at concentration of 100 ppm of (E110 and E124) and 150 ppm of (E124), an adsorbent dosage of 0.4 gL−1, and an initial pH 5. In addition, Langmuir model best fits the sorption isotherm data, with the maximum adsorption capacity at 303 K being 238 mg/g, 248.75 mg/g, and 358.25 mg/g for E110, E122, and E124, respectively. The Bt@CTAB organoclay can be regenerated up to the 4th cycle successfully. The thermodynamic studies revealed the spontaneous and exothermic nature of the adsorption of these anionic dyes onto Bt@CTAB organoclay. The prepared cationic Bt@CTAB organoclay was successfully applied for the removal of E110, E122, and E124 from real water samples, synthetic effluents, and colored soft drinks with a recovery (R%) higher than 95%. The plausible adsorption mechanism of E110, E122, and E124 onto Bt@CTAB organoclay is proposed to be due to electrostatic interaction and hydrogen bond formation. Finally, the present study shows that Bt@CTAB organoclay may be employed efficiently and effectively to remove anionic food dyes from a wide range of real water and colored soft drinks.

Synthesis, Characterization, and Adsorption Properties of Nitrogen-Doped Nanoporous Biochar: Efficient Removal of Reactive Orange 16 Dye and Colorful Effluents.

In this work, nitrogen-doped porous biochars were synthesized from spruce bark waste using a facile single-step synthesis process, with H3PO4 as the chemical activator. The effect of nitrogen doping on the carbon material's physicochemical properties and adsorption ability to adsorb the Reactive Orange 16 dye and treat synthetic effluents containing dyes were evaluated. N doping did not cause an important impact on the specific surface area values, but it did cause an increase in the microporosity (from 19% to 54% of micropores). The effect of the pH showed that the RO-16 reached its highest removal level in acidic conditions. The kinetic and equilibrium data were best fitted by the Elovich and Redlich-Peterson models, respectively. The adsorption capacities of the non-doped and doped carbon materials were 100.6 and 173.9 mg g-1, respectively. Since the biochars are highly porous, pore filling was the main adsorption mechanism, but other mechanisms such as electrostatic, hydrogen bond, Lewis acid-base, and π-π between mechanisms were also involved in the removal of RO-16 using SB-N-Biochar. The adsorbent biochar materials were used to treat synthetic wastewater containing dyes and other compounds and removal efficiencies of up to 66% were obtained. The regeneration tests have demonstrated that the nitrogen-doped biochar could be recycled and reused easily, maintaining very good adsorption performance even after five cycles. This work has demonstrated that N-doped biochar is easy to prepare and can be employed as an efficient adsorbent for dye removal, helping to open up new solutions for developing sustainable and effective adsorption processes to tackle water contamination.

Performance of ferrates for simultaneous removal of As and Mn from circumneutral contaminated mine water

Despite being efficient in removing (in)organic contaminants from effluents, ferrate (Fe(VI)) has scarcely been used for the removal of metal(loid)s from mine effluents. The present study evaluated the performance of wet vs. solid Fe(VI) to remove As(III) and Mn(II) from synthetic and surrogate neutral mine effluents. The experiments were done using single (SAs or SMn containing 3.5 mg As/L or 4.5 mg Mn/L, respectively) and binary (SAs+Mn containing 3.5 mg As/L and 4.5 mg Mn/L) synthetic effluents as well as surrogate mine effluents (Elow and Ehigh). Firstly, Fe(VI) type, optimal dose, adjusted pH (pHa), and retention time were assessed to evaluate their effect on the treatment of SAs and SMn. Then, the performance of Fe(VI)s, alone or combined with Fe(III), was tested for the removal of As and Mn from SAs+Mn. Lastly, the most performant conditions were applied to Elow and Ehigh; the toxicity to D. magna was evaluated before and after treatment. The results showed that at pHa of 5.5, Fe(VI)s efficiently removed As (> 98%) and Mn (> 97%) from SAs, SMn, and SAs+Mn within the first minute. The Fe(VI)s dose required had to be adjusted depending on the contaminant to be removed (SAs or SMn vs. SAs+Mn). The use of Fe(VI)s +Fe(III) showed improved removal efficiencies for As (99%) and Mn (> 99%), while requiring a lower Fe(VI) dose. Moreover, the Fe(VI) treatment of Ehigh, initially acutely toxic, entailed the elimination of D. magna toxicity. These findings provide new insights for the potential application of Fe(VI) in the removal of metal(loid)s from mine water.

Treatment of Synthetic Industrial Effluent Aiming at the Removal of Glyphosate by Means of Advanced Oxidation

Objective: The purpose of this study was to assess the efficiency of an advanced oxidative process gradually applying different oxidative agents, i. e. UV, TiO2 and O3, to evaluate the removal efficiency of a commercial composition of glyphosate from an aqueous matrix. Theoretical framework: In Brazil, approximately 150 million liters of glyphosate are consumed per year, representing 30% of the total pesticides used, which can contaminate surface water due to aerial or terrestrial spraying, erosion and runoff, improper disposal of commercial packaging and cleaning of contaminated spray tanks. Advanced oxidative processes have emerged as an alternative to the degradation of glyphosate since they have high efficiency in reducing organic contaminants to an acceptable limit with a low operating cost. Method: Experimental consisted of a benchtop-scale system, composed of a batch reactor with a 25W UV lamp inside and a feeding pump in a recirculation reservoir. It was responsible for performing the removal of glyphosate by means of an advanced oxidative process after receiving TiO2 and O3 application. Results and conclusion: The photolysis process obtained an efficiency of 24.69%, the photocatalytic oxidation process with TiO2 obtained 37.78%, and the photocatalytic ozonation with TiO2 obtained 45.46% efficiency in 60 minutes of reaction. The possible formation of byproducts after one hour of reaction due to the increase in concentration was also observed, since it was not possible to distinguish glyphosate from other compounds in the analysis method applied. Implications of the research: As demonstrated by the results of the experimental assays, the advanced oxidative technique proved to be very efficient to make the removal of a commercial composition of glyphosate from an aqueous matrix. Originality/value: It has been shown that it is possible to remove glyphosate in an efficient way, using a highly efficient fast technique.

Adsorption of Omeprazole on Biobased Adsorbents Doped with Si/Mg: Kinetic, Equilibrium, and Thermodynamic Studies.

This paper proposes an easy and sustainable method to prepare high-sorption capacity biobased adsorbents from wood waste. A biomass wood waste (spruce bark) was employed to fabricate a composite doped with Si and Mg and applied to adsorb an emerging contaminant (Omeprezole) from aqueous solutions, as well as synthetic effluents loaded with several emerging contaminants. The effects of Si and Mg doping on the biobased material's physicochemical properties and adsorptive performance were evaluated. Si and Mg did not influence the specific surface area values but impacted the presence of the higher number of mesopores. The kinetic and equilibrium data presented the best fitness by the Avrami Fractional order (AFO) and Liu isotherm models, respectively. The values of Qmax ranged from 72.70 to 110.2 mg g-1 (BP) and from 107.6 to 249.0 mg g-1 (BTM). The kinetic was faster for Si/Mg-doped carbon adsorbent, possibly due to different chemical features provoked by the doping process. The thermodynamic data showed that the adsorption of OME on biobased adsorbents was spontaneous and favorable at four studied temperatures (283, 293, 298, 303, 308, 313, and 318 K), with the magnitude of the adsorption correspondent to a physical adsorption process (ΔH° < 2 kJ mol-1). The adsorbents were applied to treat synthetic hospital effluents and exhibited a high percentage of removal (up to 62%). The results of this work show that the composite between spruce bark biomass and Si/Mg was an efficient adsorbent for OME removal. Therefore, this study can help open new strategies for developing sustainable and effective adsorbents to tackle water pollution.

Selenite bioreduction by a consortium of halophilic/halotolerant bacteria and/or yeasts in saline media

Selenium oxyanions are released into environments by natural and anthropogenic activities and are present in agricultural and glass manufacturing wastewater in several locations worldwide. Excessive amounts of this metalloid have adverse effects on the health of living organisms. Halophilic and halotolerant microorganisms were selected for selenium oxyanions remediation due to presence of significant amount of salt in selenium-containing wastewater. Effects of aeration, carbon sources, competitive electron acceptors, and reductase inhibitors were investigated on SeO32− bio-removal. Additionally, NO3−-containing wastewater were exploited to investigate SeO32− remediation in synthetic agricultural effluents. The results showed that the SeO32− removal extent is maximum in aerobic conditions with succinate as a carbon source. SO42− and PO43− do not significantly interfere with SeO32− reduction, while WO42− and TeO32− decrease the SeO32− removal percentage (up to 35 and 37%, respectively). Furthermore, NO3− had an adverse effect on SeO32− biotransformation by our consortia. All consortia reduced SeO32− in synthetic agricultural wastewaters with a 45–53% removal within 120 h. This study suggests that consortia of halophilic/halotolerant bacteria and yeasts could be applied to treat SeO32--contaminated drainage water. In addition, sulphates, and phosphates do not interfere with selenite bioreduction by these consortia, which makes them suitable candidates for the bioremediation of selenium-containing wastewater.

Optimal concentration and efficiency of the photo fenton system for the treatment of a synthetic textile effluent

The Photo Fenton process is an alternative process for the treatment of effluents from the textile industry, being a reagent-based chemical on Fe2+ and H2O2 + UV light, whose mechanism consists of oxidizing the pollutants until they are suitable for discharge into bodies of water. This research seeks to determine the optimum concentration of Fe2+ - H2O2 in the treatment of a synthetic textile effluent and, subsequently, to evaluate the efficiency of the system. The synthetic textile effluent was prepared under laboratory conditions, FeSO4 and H2O2 were added at different concentrations, with exposure to UV-A light throughout the process, and it was determined that the optimum concentration of the Photo Fenton reagent was 400 mg L-1 of FeSO4 and 12 ml L-1 of H2O2, a dosage that reduced initial turbidity, color, and COD by 100%, 99% and 83%, respectively, and increased the DO by 11%. Turbidity removal was obtained by carrying out the treatment in an acid medium (pH 3). The presence of Fe2+ promoted the significant removal of COD. The increase in DO was obtained by the presence of H2O2 and UV-A light, and this in turn, had a considerable influence on the removal of effluent color. Regarding the efficiency of the system, it was determined that the Photo Fenton reagent is an excellent alternative for the treatment of textile effluents with high and low organic loads, reducing contaminants derived from industry processes.&#x0D; Keywords: clean technology, Fe2+-H2O2, organic, oxidation, pollution, water.

Application of Immersed Membrane Bioreactor for Semi-Continuous Production of Polyhydroxyalkanoates from Organic Waste-Based Volatile Fatty Acids.

Volatile fatty acids (VFAs) appear to be an economical carbon feedstock for the cost-effective production of polyhydroxyalkanoates (PHAs). The use of VFAs, however, could impose a drawback of substrate inhibition at high concentrations, resulting in low microbial PHA productivity in batch cultivations. In this regard, retaining high cell density using immersed membrane bioreactor (iMBR) in a (semi-) continuous process could enhance production yields. In this study, an iMBR with a flat-sheet membrane was applied for semi-continuous cultivation and recovery of Cupriavidus necator in a bench-scale bioreactor using VFAs as the sole carbon source. The cultivation was prolonged up to 128 h under an interval feed of 5 g/L VFAs at a dilution rate of 0.15 (d-1), yielding a maximum biomass and PHA production of 6.6 and 2.8 g/L, respectively. Potato liquor and apple pomace-based VFAs with a total concentration of 8.8 g/L were also successfully used in the iMBR, rendering the highest PHA content of 1.3 g/L after 128 h of cultivation. The PHAs obtained from both synthetic and real VFA effluents were affirmed to be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a crystallinity degree of 23.8 and 9.6%, respectively. The application of iMBR could open an opportunity for semi-continuous production of PHA, increasing the feasibility of upscaling PHA production using waste-based VFAs.

Circular Economy Approach to Enhance Soil Fertility Based on Recovering Phosphorus from Wastewater

Phosphorus (P) is a non-renewable resource whose future scarcity will constrain agricultural sustainability. Thus, to ensure this sustainability, a circular economy approach involving the use of recycled P sources is needed. The objective of this study was to assess the fertilizer effect of two recycled P products that can be obtained from water purification: vivianites and struvites. Five vivianites (one synthetic, one obtained from industrial process, and three from water purification) and two struvites (named A and B) from diverse origins were compared with soluble mineral P fertilizer (superphosphate) in a pot experiment using wheat at two P rates (50 and 100 mg P kg−1) in two Mediterranean soils. Struvites performed similarly to superphosphate and outperformed all types of vivianites in terms of dry matter (DM) yield and P uptake. Industrial and synthetic vivianites, led to higher DM yield and P uptake by plants than vivianites from water purification. Synthetic and industrial process vivianites increased Olsen P in soils after harvesting, relative to non-fertilized soils. Differences between vivianites can be explained by the different Fe2+ to Fe3+ ratios, the different crystal sizes, and morphology. Struvite B can replace 65–92% superphosphate on a P uptake basis, and 94–154% on a DM yield basis (the range depends on the P rate). Vivianite from industrial process can replace 54–75% of superphosphate on a DM basis, depending on the P rate. Thus, struvites were as efficient as superphosphate as P fertilizer. However, the results obtained with industrial process vivianite are promising with a view to its potential use in agriculture.

Evaluation of the decolorization potential of azo dyes by aerobic granular sludge

This study assessed the azo dye decolorization potential by aerobic granular sludge (AGS), particularly investigating the effects of different electron donor substrates, redox mediators, dye structures, and alternative electron acceptors. Additionally, the stability and performance of an AGS reactor were evaluated during the treatment of a synthetic azo dye-containing effluent in the absence and presence of a redox mediator. Propionate and anthraquinone-2-sulfonate (AQS) were the best substrate (k1 1.1–1.9-fold higher) and redox mediator (k1 1.4-fold higher), respectively, for Reactive Black 5 (RB5) decolorization. AQS (50 μM) had a greater impact on Reactive Orange 16 (k1 = 15.60 h−1) than on Reactive Red 120 (k1 = 0.48 h−1) and RB5 (k1 = 7.92 h−1). Nitrate and sulfate (100 and 200 mg·L−1) inhibited dye reduction (decreasing k1 from 5.52 to 0.72 and 2.40 h−1, respectively), possibly because they compete with the dye for the electrons in the environment. However, AQS minimized their impact on this process (except for nitrate at 200 mg·L−1). In the reactor, RB5 and AQS did not alter the physical characteristics of AGS and its ability to remove organic matter and nutrients. Finally, the effect of AQS on decolorization was not so intense, increasing only ∼15%.

Flax fiber based semicarbazide biosorbent for removal of Cr(VI) and Alizarin Red S dye from wastewater

In the present study, flax fiber based semicarbazide biosorbent was prepared in two successive steps. In the first step, flax fibers were oxidized using potassium periodate (KIO4) to yield diadehyde cellulose (DAC). Dialdehyde cellulose was, then, refluxed with semicarbazide.HCl to produce the semicarbazide functionalized dialdehyde cellulose (DAC@SC). The prepared DAC@SC biosorbent was characterized using Brunauer, Emmett and Teller (BET) and N2 adsorption isotherm, point of zero charge (pHPZC), elemental analysis (C:H:N), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The DAC@SC biosorbent was applied for the removal of the hexavalent chromium (Cr(VI)) ions and the alizarin red S (ARS) anionic dye (individually and in mixture). Experimental variables such as temperature, pH, and concentrations were optimized in detail. The monolayer adsorption capacities from the Langmuir isotherm model were 97.4 mg/g and 18.84 for Cr(VI) and ARS, respectively. The adsorption kinetics of DAC@SC indicated that the adsorption process fit PSO kinetic model. The obtained negative values of ΔG and ΔH indicated that the adsorption of Cr(VI) and ARS onto DAC@SC is a spontaneous and exothermic process. The DAC@SC biocomposite was successfully applied for the removal of Cr(VI) and ARS from synthetic effluents and real wastewater samples with a recovery (R, %) more than 90%. The prepared DAC@SC was regenerated using 0.1 M K2CO3 eluent. The plausible adsorption mechanism of Cr(VI) and ARS onto the surface of DAC@SC biocomposite was elucidated.

Systematic computational toxicity analysis of the ozonolytic degraded compounds of azo dyes: Quantitative structure-activity relationship (QSAR) and adverse outcome pathway (AOP) based approach

The present study identifies and analyses the degraded products of three azo dyes (Reactive Orange 16, Reactive Red 120, and Direct Red 80) and proffers their in silico toxicity predictions. In our previously published work, the synthetic dye effluents were degraded using an ozonolysis-based Advanced Oxidation Process. In the present study, the degraded products of the three dyes were analysed using GC-MS at endpoint strategy and further subjected to in silico toxicity analysis using Toxicity Estimation Software Tool (TEST), Prediction Of TOXicity of chemicals (ProTox-II), and Estimation Programs Interface Suite (EPI Suite). Several physiological toxicity endpoints, such as hepatotoxicity, carcinogenicity, mutagenicity, cellular and molecular interactions, were considered to assess the Quantitative Structure-Activity Relationships (QSAR) and adverse outcome pathways. The environmental fate of the by-products in terms of their biodegradability and possible bioaccumulation was also assessed. Results of ProTox-II suggested that the azo dye degradation products are carcinogenic, immunotoxic, and cytotoxic and displayed toxicity towards Androgen Receptor and Mitochondrial Membrane Potential. TEST results predicted LC50 and IGC50 values for three organisms Tetrahymena pyriformis, Daphnia magna, and Pimephales promelas. EPISUITE software via the BCFBAF module surmises that the degradation products' bioaccumulation (BAF) and bioconcentration factors (BCF) are high. The cumulative inference of the results suggests that most degradation by-products are toxic and need further remediation strategies. The study aims to complement existing tests to predict toxicity and prioritise the elimination/reduction of harmful degradation products of primary treatment procedures. The novelty of this study is that it streamlines in silico approaches to predict the nature of toxicity of degradation by-products of toxic industrial affluents like azo dyes. These approaches can assist the first phase of toxicology assessments for any pollutant for regulatory decision-making bodies to chalk out appropriate action plans for their remediation.

Valorization potential of N-rich zeolite and moving bed biofilm reactor (MBBR) biomass in the revegetation of non-acid generating gold mine tailings

Treatment of ammonia nitrogen (NH3−N) in mine effluents generates N-rich residual materials, such as moving bed biofilm reactor (MBBR) biomass and spent zeolite. Using them as substitutes for mineral fertilizers in revegetation of mine tailings avoids disposal and contributes to a circular economy. The study evaluated the effect of MBBR biomass and N-rich zeolite amendments on above- and below-ground growth and foliar nutrient and trace element concentrations of a legume and several graminoid species grown on non-acid generating gold mine tailings. N-rich zeolite (clinoptilolite) was produced by treating saline (up to 60 mS/cm) synthetic and real mine effluents (250 vs 280 mg/L NH3-N). A three-month pot experiment was conducted with a dose of tested amendments equivalent to 100 kg/ha N and compared to unamended tailings (as negative control), tailings with a mineral NPK fertilizer, and a topsoil (as positive controls). Higher foliar N concentrations were found in amended and fertilized tailings vs negative control, but N was less available in the zeolite treatments than in other tailings treatments. For all plant species, the mean leaf area and above-ground, root, and total biomasses were similar in the zeolite-amended tailings to the unamended tailings, while the MBBR biomass amendment resulted in similar above- and below-ground growth to the NPK fertilized tailings and the commercial topsoil. Trace metal concentrations in water leaching from the amended tailings remained low, but tailings amended with zeolite exported NO3-N concentrations up to 10 times greater (>200 mg/L) after 28 days compared to all other treatments. Foliar Na concentrations in zeolite mixtures were six to nine times higher than in other treatments. The MBBR biomass is a promising potential amendment for revegetation of mine tailings. However, Se concentrations in plants after MBBR biomass amendment should not be underestimated, while Cr transfer from tailings to plants was observed.

Thin-Film Nanocomposite Membranes with Nature-Inspired MOFs Incorporated for Removing Fluoroquinolone Antibiotics

A nanofiltration membrane functionalized with metal-organic frameworks (MOFs) is promising to enhance micropollutant removal and realize wastewater reclamation. However, the current MOF-based nanofiltration membranes still suffer from severe fouling problems with an indefinable mechanism when used for antibiotic wastewater treatment. Hence, we report a nature-inspired MOF-based thin-film nanocomposite (TFN-CU) membrane to explore its rejection and antifouling behavior. Compared with unmodified membranes, the optimal TFN-CU5 membrane (with 5 mg·mL-1 C-UiO-66-NH2) had high water permeance (17.66 ± 1.19 L·m-2·h-1·bar-1), exceptional rejection for norfloxacin (97.92 ± 2.28%) and ofloxacin (95.36 ± 1.03%), and excellent long-term stability for treating synthetic secondary effluent with antibiotic rejection over 90%. Furthermore, it also showed superior antifouling capability (flux recovery up to 95.86 ± 1.28%) in bovine serum albumin (BSA) filtration after fouling cycles. Deriving from the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) approach, the antifouling mechanism between BSA and the TFN-CU5 membrane was mainly attributed to the inhibited adhesion forces because the growing short-ranged acid-base interaction caused repulsive interfacial interactions. It is further revealed that BSA fouling behavior is slightly retarded under an alkaline environment, while strengthened in the presence of calcium ions and humic acid, as well as high ionic strength. In short, the nature-inspired MOF-based TFN membranes possess exceptional rejection and organic fouling resistance, giving insights into the design of antifouling membranes during antibiotic wastewater reclamation.

A novel bio-adsorbent development from tannery solid waste derived biodegradable keratin for the removal of hazardous chromium: A cleaner and circular economy approach

The chromium (Cr) used in leather processing has well-known negative impacts on the environment, as the disposing of tannery effluent contains a significant amount of Cr. Alongside this, the tanning industry also generates a large amount of solid keratinous waste during the unhairing process, which also burdens to the environment. There is an urgency to recover this Cr from tannery wastewater and manage yielded solid waste by adopting an affordable and ecologically beneficial alternative. Previous studies attempted to develop bio-adsorbent from other types of bio-waste, and could not show the circular way of the reusing process of recovered Cr. Also, there needs to be more studies on bio-adsorbent preparation from tannery solid waste. This study developed a novel biodegradable film as a bio-adsorbent from keratinous waste and examined its suitability to recover Cr from tannery wastewater. The recovered Cr has been reused in the tanning process. The removal of Cr from synthetic and actual tanning effluent was optimized using a multivariate approach using Central Composite Design under Response Surface Methodology, with a removal efficiency of 91.247% and 86.972%, respectively. A desorption investigation was performed, and the analysis showed that the films could be reused, and Cr can be recovered at a pH of around 10.5. Recovered Cr from wastewater was also utilized as basic Cr sulfate in tanning. Several experimental analyses of the obtained leather demonstrated good hydrothermal stability, Cr content, and physical properties with the negligible difference compared to conventionally processed leather. Experiment on the biosorption technique was also conducted to further understand the interaction and industrial feasibility of the technology. Overall, the findings encourage the ‘use of solid waste for treatment of liquid waste’, a circular economy approach that would contribute to cleaner leather production.

Nickel-aluminium layered double hydroxide as an efficient adsorbent to selectively recover praseodymium and samarium from phosphogypsum leachate

This study aimed to synthesize a green powdered layered double hydroxide (LDH) based on nickel-aluminum (Ni–Al-LDH) to evaluate its efficiency in the removal of rare earth elements (REEs), Praseodymium (Pr3+) and Samarium (Sm3+), from synthetic effluents and real leachate using phosphogypsum as a secondary source of REEs. Several characterization techniques were employed to evaluate the physicochemical properties of Ni-Al-LDH adsorbent, such as specific surface area and porosity, functional surface groups and phases, and point of zero charge. The characterization results indicated that Ni-Al-LDH exhibited a typical layered structure confirming the successful synthesis. The effect of key adsorption variables, such as pH, contact time, initial concentration, and temperature, on the REEs adsorption was extensively studied in single-factor experiments separately. The kinetic and equilibrium adsorption data agreeably fitted the Avrami and Sips models, respectively. The maximum adsorption capacities for Pr3+ and Sm3+ adsorption were 18.13 and 15.68 mg g−1 at 298 K, respectively. The thermodynamic parameters (ΔH0, ΔS0, ΔG0) indicated that the adsorption was spontaneous, favorable, and exothermic for both Pr3+ and Sm3+. The interactions between Pr3+ and Sm3+ onto Ni-Al-LDH suggest that multiple adsorption mechanisms are involved, such as ion exchange, precipitation, chelation, and pore filling. Finally, the Ni-Al-LDH could selectively recover REEs, specially Pr3+ and Sm3+, from the real phosphogypsum leachate. It has been demonstrated that Ni-Al-LDH is a promising adsorbent material that could be used as an adsorbent for the recovery of REEs from synthetic and real effluents.

PPCPs abatement using TiO2-based catalysts by photocatalytic oxidation and ozonation: The effect of nitrogen and cerium loads on the degradation performance and toxicity impact

Pharmaceutical and personal care products (PPCPs) have been consumed in great extension and most of these are found in water bodies, owing to the inefficiency of conventional wastewater treatments. To face against these recalcitrant contaminants, advanced oxidation processes such as photocatalysis and ozonation have been studied. Moreover, the combination of these technologies can improve the degradation of PPCPs, reducing the ozone consumption and the effluent toxicity with the presence of photocatalysts. In particular, this study aimed to evaluate the effects of different N and Ce loads in co-doping TiO2 catalysts on the efficiency of photocatalytic oxidation and photocatalytic ozonation for PPCPs abatement, as well as on the resultant toxicity to aquatic species. Different radiation sources (UVA and solar radiation) were considered for the photocatalytic oxidation. A mixture of 5 PPCPs: paracetamol, sulfamethoxazole, carbamazepine, methylparaben and propylparaben was used as a model synthetic effluent. Photocatalysis showed a low efficiency on the PPCPs removal (<20 %), which was not affected by the radiation source. In general, the tested catalysts showed no or low added-value for reducing the toxicity of the synthetic effluent. Concerning photocatalytic ozonation, the lowest N amount (2.5 % w/w) promoted the best results for PPCPs removal, achieving values up to 100 % with significant reduction of ozone dose compared to photolytic ozonation. In general, photocatalytic ozonation showed better ecotoxicological performance than single photocatalysis. Compared to single photolytic ozonation, a benefitial effect was observed for two aquatic species, using a specific catalyst. This catalyst, prepared by doping TiO2 with 2.5 % w/w N and 1.2 % w/w Ce, showed to be the most promisong one, with potential to be used in photocatalytic ozonation. Hence, this work highlights the potential role of N and Ce co-doped TiO2-based catalysts in photocatalytic ozonation for wastewater treatment.