Zeolitic materials are effective adsorbents for ammonium and phosphate. However, their practical deployment is often constrained by limited availability of natural zeolites and potential risks associated with industrial waste-derived alternatives. In this study, lake sediment was utilized as a geochemically compatible precursor to synthesize zeolite and Al-modified zeolite (AMZ) for ammonium and phosphate removal. Structural and compositional analyses confirmed the transformation of sediment into mixed-phase zeolitic materials with developed porosity, abundant exchangeable Na+ sites and amorphous Al-rich surface phases, leading to enhanced surface area and reactive Al-OH functionalities. The adsorption capacities of NH4+/PO43-increased from sediment (0.28/ 0.39 mg/g) to zeolite (43.03/15.02 mg/g) and AMZ (33.87/27.10 mg/g). Adsorption kinetics followed a pseudo-second-order model, with faster uptake of NH4+ than PO43-. Although the optimal pH ranges for NH4+ and PO4 3adsorption differed, simultaneous removal was achieved at pH 7.0-8.0 under environmentally relevant conditions. Competitive adsorption experiments indicated negligible anion interference on phosphate uptake, whereas ammonium removal was dominantly governed by ion exchange and inhibited by coexisting cations. XPS analysis revealed that phosphate immobilization occurred via inner-sphere Al-O-P complexation. Sediment incubation experiments demonstrated sustained reductions of NH4+, PO43-and Fe2+ under both oxic and anoxic conditions. These results indicate that sediment-derived zeolitic materials offer an environmentally compatible strategy for mitigating internal nutrient loading in eutrophic lakes.

Lanthanum-based phosphorus inactivation agents (PIAs) are widely used to mitigate internal phosphorus (P) loading in eutrophic lakes, yet their performance is commonly assessed by sequential extraction of PIA-amended sediments. When reactive PIA particles remain in the sediment matrix, phosphate released during extraction may re-adsorb onto remaining reactive PIA surfaces, leading to overestimation of apparent P immobilization. Here, we synthesized magnetically recoverable magnetite/lanthanum hydroxide beads (MLaB) as a model La-based PIA to isolate and quantify this bias in a controlled anoxic sediment-water system using homogenized sediment. Magnetic recovery allowed sediment fractionation to be performed with and without prior MLaB removal and enabled direct quantification of P accumulated on the recovered MLaB. Compared with separated samples, non-separated fractionation overestimated depletion of releasable sediment P by 8.42% and 13.06% at the low and high dosages, respectively, with the bias mainly expressed in BD-P and NaOH-P. Across all sampling points, P measured on recovered MLaB closely matched system-scale reactive P depletion, clustering near the 1:1 relationship with a mean absolute deviation of 5.23%. La L3-edge X-ray absorption spectroscopy further showed that immobilized P was associated with rhabdophane-like LaPO4·nH2O phases. These results demonstrate that magnetic recovery of a model La-based inactivation agent can identify extraction-induced overestimation and provide a direct, mass-conservative endpoint for assessing P immobilization by the MLaB phase.

Free-floating aquatic plants are important invasive alien species whose excessive growth strongly affects freshwater ecosystems and their ecological service functions worldwide. Due to their rapid reproduction rate and the difficulty in their removal using common methods, the management of these aquatic weeds is still challenging. In this study, we proposed a strategy to control giant duckweed (Spirodela polyrhiza) in a highly eutrophic pond by blocking the supply of phosphorus by greatly lowering the phosphorus concentration in water using Zeofixer (R), a novel lanthanum-containing P-inactivation agent. We found that the application of Zeofixer (R) satisfactorily eliminated the aquatic weed from the study pond. Zeofixer (R) had a high affinity for phosphate with a maximum adsorption capacity of 21.19 mgP/g, and it reduced the concentration of dissolved inorganic P, which was the major form of P species in the pond, from 1.60 to 0.005 mg/L. Amendment of pond sediment with Zeofixer (R) greatly diminished the P concentration in water under either oxic or anoxic conditions, although the latter caused a great release of P from sediment when compared with the former. After Zeofixer (R) treatment, the releasable P fractions in the sediment were substantially converted to stable P fractions, enabling the inactivation of P and the retardation of future P release. In conclusion, the free-floating aquatic plants in bodies of water could be thoroughly and permanently controlled using P-inactivation agents.

Aiming at the development of ecologically safe and environmentally friendly materials to immobilize both anionic and cationic pollutants in eutrophic lakes, we have attempted to synthesize zeolites and aluminum-modified zeolites (AMZs) from four lake sediments by a fusion-assisted hydrothermal method. Characteriza-tion by X-ray fluorescence spectrometry, X-ray diffraction analysis, Fourier-transform infrared spectrometry, scanning electron microscopy, and specific surface area measurements confirmed that zeolites including Na-X, Na-P1, and hydroxysodalite were successfully synthesized, and the AMZs composed of zeolite and amorphous hydrous aluminum oxide were formed. The cation-exchange capacity (representing the ability to adsorb cationic pollutants) and the phosphate adsorptive capacity (representing the ability to adsorb anionic pollutants) of ze-olites (204.3-305.7 cmol/kg and 9.3-16.3 mgP/g, respectively) and AMZs (105.7-309.2 cmol/kg and 26.8-38.9 mgP/g, respectively) were much higher than those of the original lake sediments (3.7-6.4 cmol/kg and 0.5-1.7 mgP/g, respectively). Incubation of sediment in lake water under anoxic conditions, which are commonly encountered at the beds of eutrophic lakes, triggered substantial release of phosphorus, iron, manganese, and ammonium, but amendment with AMZ significantly reduced the concentrations of these pollutants in the overlying water. Our findings demonstrated that zeolite and AMZ synthesized from lake sediments may be applied as suitable materials for the remediation of eutrophic lakes.

Defluoridation of water is still challenging due to the fluoride pollution of both groundwater and surface water worldwide. In this study, lanthanum-modified zeolite (LMZ) was synthesized from coal fly ash and was investigated for fluoride removal from water by conducting batch and column experiments. Our results indicated that the process of fluoride adsorption was endothermic and the adsorption kinetics on LMZ followed the pseudosecond-order model. A higher temperature increased both the capacity and the rate of adsorption. The maximum fluoride adsorption capacity of LMZ reached 141.5 mg/g with a F/La molar ratio of 4.21, as estimated from the Langmuir model which best fitted the isotherm data. Fluoride adsorption greatly depended on pH, with optimal performance being achieved within similar to 5.0-similar to 7.0. The point of zero charge of LMZ was pH 8.8, at which only bicarbonate ions greatly affected fluoride removal. However, no competing effect was observed at pH 6.3 for all tested anions including chloride, sulphate, nitrate, bicarbonate and acetate. The dominant adsorption mechanism was the ligand exchange of fluoride with hydroxyls on LMZ, as illustrated by the rise in pH due to fluoride adsorption and by the molecular scale spectroscopic FTIR, Raman and XPS studies. Fluoride adsorbed on LMZ was successfully desorbed using NaOH solution, and regenerated LMZ could be reused. The results of column studies showed that LMZ granulated with alginate performed well in treating F-containing water. In conclusion, LMZ is a promising material for efficient defluoridation from water.

The removal and recovery of phosphate from water using adsorption technology require that the adsorbent material is easily separable from treated water. Continuous efforts are still awaited to develop additional efficient phosphate adsorbents that are economical to fabricate. In this study, hydrous zirconia-impregnated chitosan beads (HZCB) containing different Zr/chitosan ratios were synthesized using a facile scheme. We found that HZCB with a Zr/amine molar ratio of ~ 1 (HZCB-1) possessed excellent stability and phosphate removal performance. This optimized material was characterized with XRD, SEM, FTIR, XPS, specific surface area and point of zero charge measurements. The maximum adsorption capacity was 42.02 mg/g (at pH ~ 6.7). The adsorption kinetics were best described by a pseudosecond-order model, and the rate constant of HZCB-1 was much lower than that of its powder but was similar to the commercial bead product Ferrolox. The removal of phosphate depended substantially upon pH and was enhanced by lowering the pH. Good selectivity of HZCB-1 for phosphate was observed, although the coexistence of sulfate produced a significant negative effect. Direct coordination of phosphate to Zr atoms by replacing hydroxyls was the dominant adsorption mechanism (~ 85%), while chitosan also contributed to phosphate removal (~ 15%). Adsorbed phosphate was successfully eluted by an NaOH solution, and the material obtained after desorption and regeneration was able to be repeatedly used. The results of column studies indicated that this material could be implemented in long-term application.

The removal of fluoride from wastewater is essential as the excess accumulation of fluoride in environment is harmful to the health of humans. In this study, the defluorination of water by aluminum hydroxide-coated zeolite (AHZ), which was synthesized from coal fly ash, was investigated in batches. The Langmuir maximum adsorption capacity of fluoride by AHZ reached 18.12 mg/g. Aluminum hydroxide was shown to be the major component that adsorbed fluoride. More than 92% removal of fluoride was achieved within 2 h, and the fluoride adsorption kinetics were well fitted to a pseudo-second-order model. The point of zero charge (pHpzc) of the AHZ was determined to be 5.52. Fluoride adsorption by AHZ depended greatly on pH, and maximum performance was obtained at pH 5.5-6.5. The AHZ showed good selectivity for the adsorption of fluoride in the presence of chloride, nitrate, sulfate, bicarbonate, and acetate ions, and the fluoride was nearly exhausted at a sufficiently high dose. The release of OH- due to fluoride adsorption was confirmed. FTIR and XPS studies further illustrated that the adsorption mechanism of fluoride adsorption on AHZ was ligand exchange with hydroxyl groups and the formation of F-Al bonds.

Modification of graphene oxide (GO) with polyethyleneimine (PEI) has been studied to develop a GO/PEI sponge material that not only performs well in the adsorption of Cu(II) but also is easily separated from water. The results showed that GO had excellent affinity for PEI, and GO/PEI prepared at pH 9.0 using PEI with a MW of 70,000 was shown to be a good adsorbent for Cu(II). This GO/PEI was characterized with SEM, XRD, XPS, FTIR and TG analyses and was investigated for Cu(II) adsorption further. The adsorption isotherm data of Cu(II) were fitted well with the Langmuir model, from which the maximum adsorption of GO/PEI was calculated to be 150.9 mg/g at pH 5.5. This was much higher than that of GO and two commercial resins. GO/PEI showed high selectivity towards Cu(II). In GO/PEI, the contributions of amino groups on PEI and negative charges on GO were 79.2% and 20.8%, respectively. Cu(II) adsorption on GO/PEI decreased with decreasing pH, and 1 M HCl caused nearly complete desorption of the adsorbed Cu(II). Experimental results of five cycles of adsorption-desorption indicated that this material could be reused. Column studies showed that GO/PEI performed well in terms of both Cu(II) adsorption and stability in water.

Wind-driven waves and currents in shallow lakes frequently trigger the resuspension of sediments in the photic layer, which is characterized with a high pH and high dissolved organic carbon (DOC) concentration. The mechanism of phosphorus-inactivating agents (PIAs) immobilizing phosphorus under the coupled influence of pH and DOC is not clarified, and the applicability of PIAs in eutrophic shallow lakes is thus still doubtful. We found that, under the coupled influence of pH and DOC, the uptake of phosphate by LMZ was affected mainly by pH at low DOC concentrations and by DOC at high DOC concentrations. A high pH (9.3) and high DOC concentration (24.7 mg/L) greatly increased the release of phosphorus from sediment to water. However, the addition of LMZ substantially reduced the P concentrations in water, mainly via capture of dissolved inorganic phosphorus. The results of the reversibility of the adsorption of phosphates and DOC showed that phosphate had much higher affinity than DOC towards LMZ. The phosphate once adsorbed on LMZ was resistant to release when exposed to conditions of either a high pH (9.5), high DOC concentration (250 mg/L) or both; i.e., only <5% of the adsorbed phosphate is releasable. Therefore, we proposed that, to avoid the coupled influence of pH and DOC in the photic layer of eutrophic shallow lakes, LMZ could be applied in multiple low doses in the season when the growth of algae is minimal (a low pH and low DOC concentration).

To enhance the reducing sugar yield in enzymatic hydrolysis, various factors (NaOH concentration, solid content and pre-treatment time) that affect the pre-treatment process were investigated and evaluated based on the reducing sugar yield of the subsequent enzymatic hydrolysis. The enzymatic hydrolysis was based on the cellulase from Trichoderma reesi ATCC 26921, the optimum NaOH pre-treatment conditions were an NaOH concentration of 1.0% (w/w), a solid content of 5.0% (w/v) and a pre-treatment time of 60 min. Various parameters that affect the enzymatic hydrolysis of wheat straw, including the solid content, enzyme loading, pH and hydrolysis time, were investigated and optimized through a Box–Behnken design and response surface methodology. The predicted optimum conditions for enzymatic hydrolysis were a solid content of 8.0% (w/v), an enzyme loading of 35 FPU/g substrate, a temperature of 50 °C, a pH of 5.3 and a hydrolysis time of 96 h. The experimental result showed that the maximum reducing sugar yield was 60.73% (53.35% higher than the wheat straw without NaOH pre-treatment), which is in accordance with the predicted conditions.

Abstract Surfactants, especially non-ionic surfactants, play an important role in the preparation of nanocarriers and can also promote the enzymatic hydrolysis of lignocellulose. A broad overview of the current status of surfactants on the immobilization of cellulase is provided in this review. In addition, the restricting factors in cellulase immobilization in the complex multiphase hydrolysis system are discussed, including the carrier structure characteristics, solid-solid contact obstacles, external diffusion resistance, limited recycling frequency, and invalid combination of enzyme active centers. Furthermore, promising prospects of cellulase-oriented immobilization are proposed, including the hydrophilic-hydrophobic interaction of surfactants and cellulase in the oil-water reaction system, the reversed micelle system of surfactants, and the possible oriented immobilization mechanism.

The utilization of nutrients in sewage sludge partly alleviates the economic and environmental constraints, and the composting process has been proved a cost-efficient and simple approach for the recycling of sewage sludge. During the bio-oxidative process, the thermophilic phase is considered to be the most effective stage for the biodegradation of organic matter in sewage sludge composting systems. However, the maximum temperatures of conventional thermophilic composting systems only reach approximately 55–60 °C because of the activity limitations of thermophiles at higher temperatures. Notably, increasing temperatures can accelerate the humification process and shorten the composting cycle. Therefore, the effect of rising temperature on sewage sludge composting was examined as a specific mechanism. Further, the consequent hyperthermophilic composting (HTC) system created by rising temperatures was reviewed. Moreover, the potential techno-economic advantages and future challenges of HTC systems were discussed. Finally, the microbial communities necessary to ensure the efficiency of HTC systems were analyzed and suitable hyperthermophiles for sludge HTC systems were proposed.

Contamination of water streams by dyes and heavy metals has become a major problem due to their persistence, accumulation, and toxicity. Therefore, it is essential to eliminate and/or reduce these contaminants before discharge into the natural environment. In recent years, 3D graphene has drawn intense research interests owing to its large surface area, superior charge conductivity, and thermal conductivity properties. Due to their unique surface and structural properties, 3D graphene-based materials (3D GBMs) are regarded as ideal adsorbents for decontamination and show great potential in wastewater or exhaust gas treatment. Here, this minireview summarizes the recent progress on 3D GBMs synthesis and their applications for adsorbing dyes and heavy metals from wastewater based on the structures and properties of 3D GBMs, which provides valuable insights into 3D GBMs' application in the environmental field.

Two-dimensional graphene oxide was modified with mercaptoethylamine and then treated with sodium dithionite to produce a 3D thiol-grafted graphene oxide (TGO) composite, which was investigated for the highly selective recovery of silver ions from water. Scanning electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the material before and after Ag+ adsorption. Batch adsorption experiments were carried out as a function of the initial Ag+ concentration, agitation time, temperature, and pH. The maximum adsorptive capacity of Ag+ by TGO, obtained from the Langmuir model, which fit the isotherm data well, reached 134.1 mg/g at 25 degrees C and a pH of 5.0. In addition, the adsorption was an endothermic process, and the adsorption kinetics followed the pseudo-second-order model. TGO was highly selective for Ag+; the selectivity factor of Ag+ reached 445 compared to Cu2+ ions and exceeded 1900 compared to Zn2+, Mg2+, Ca2+, Na+, and K+ ions. The adsorption of Ag+ on TGO induced the release of H+, and increased adsorption with increasing pH was observed. The adsorbed Ag+ can be proportionally desorbed using 1% HNO3. The reusability of TGO was confirmed by five cycles of adsorption-desorption-regeneration. The adsorption column studies indicated that TGO was stable in water and can be used as a filtering material for Ag+ recovery. The binding mechanism of Ag+ by TGO was proposed as the coordination of Ag+ with the sulfur atom of the mercapto groups attached to TGO followed by the reduction of Ag+ to Ag-0. (C) 2021 Elsevier Ltd. All rights reserved.

Hyperthermophilic microorganisms play a key role in the hyper-thermophilic composting (HTC) technique. However, little information is available about the hyperthermophilic microorganisms prevalent in HTC systems, except for the Calditerricola satsumensis, Calditerricola yamamurae, and Thermaerobacter. To obtain effective hyper-thermophilic microorganisms, a continuous thermo-acclimation of the suitable thermophilic microorganisms was demonstrated in this study. Bacillus thermoamylovorans with high-temperature endurance (70 °C) were newly isolated from sludge composting, and an adequate slow heating rate (2 °C per cycle) was applied to further improve its thermostability. Finally, a strain with a maximum growth temperature of 80 °C was obtained. Moreover, structural and hydrophobic changes in cell proteins, the special amino acid content ratio, and the membrane permeability of the thermophilic bacterium after thermo-acclimation were evaluated for improved thermostability. In addition, the acclimated hyperthermophilic bacterium was further inoculated into the HTC system, and an excellent performance with a maximum operating temperature of 82 °C was observed.

Recently, environmental DNA (eDNA) metabarcoding techniques have been applied to biodiversity investigations in aquatic ecosystems. However, no study has yet tested whether this technique is effective for water bodies in which extensive algal blooms break out. In this study, fish eDNA metabarcoding was carried out in Lake Taihu, which experiences extensive algal blooms, to confirm whether the technique is also effective for fish diversity research in ecosystems with frequent and extensive blooms. In December 2016, three samples were collected, including one collected in the presence of algal blooms and two collected in the absence of algal blooms. In August 2017, six samples were collected, including three collected in the presence of algal blooms and three in the absence of algal blooms. Equal amount of water samples (1 L) was collected from each site; however, the actual amount of filtrate varied with the site. Twenty-seven freshwater fish species were detected from the water samples collected in Lake Taihu. The results showed that the composition of the detected species did not differ whether or not blooms were present. However, the amount of filtration could influence the number of species detected. The results suggest that future eDNA metabarcoding studies under similar water environments should increase the amount of filtration to maximize number of species detected.

Phosphorus-inactivating agents (PIAs) as geoengineering tools in lakes have been investigated extensively, but PIA resuspension in the photic layer occurs frequently in shallow lakes and little is known about the influence of algae on PIA performance. Our results proved that algae increased the dissolved oxygen, pH and dissolved organic carbon concentration substantially. In the absence of sediment, lanthanum modified zeolite (LMZ) as a representative PIA and algae could deplete dissolved inorganic phosphorus (DIP) from water but the former was faster than the latter. When LMZ and algae coexisted, the amount of phosphorus that was captured by LMZ was 3.1 times greater than that taken up by algae. An increase in pH or dissolved organic carbon increased the zero-equilibrium phosphorus concentration (EPC0) of the sediment but LMZ addition could lower the EPC0 and reduce the risk of phosphorus release during the algal blooming season. In the presence of sediment, LMZ reduced the DIP concentration more rapidly and yielded a lower final DIP concentration compared with algae. In conclusion, the influence of algae on the performance of LMZ by (i) taking up DIP to reduce the availability of DIP and convert DIP into a releasable phosphorus form and (ii) increasing the pH and dissolved organic carbon concentration to hinder the adsorption ability of DIP were recognized. The LMZ performed well, even in the presence of algae.

Monolayers of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane have been established on magnetite nanoparticles to develop a novel magnetic adsorbent for fast decontamination of hexavalent chromium (Cr(VI)) from water. Results indicated that monolayer adsorption of the silane from water took place at low concentrations (<300 mg/L) and around 100% surface coverage was obtained at temperatures >= 90 degrees C. The hydrolysed silane was anchored to the magnetite surface through condensation reactions between its silanol groups and the surface hydroxyl groups of magnetite. The functional amine groups were protonated by acid treatment for adsorbing Cr(VI). The monolayer of the silane on magnetite (MSM) with approximately 100% surface coverage showed extremely rapid adsorption kinetics for Cr(VI), such that the process was complete within 1 min. This enables the treatment of large amounts of sewage per unit time. The adsorption capacity for Cr(VI) was 8.0 mg/g, as estimated from the Langmuir isotherm model. The saturation magnetization of the MSM reached 64.16 emu/g, allowing easy magnetic recovery from water. In the presence of up to 50-fold molar excesses of chloride and nitrate anions, little effect on Cr(VI) removal was seen, but moderate and large impacts were observed with sulphate and hydroxyl anions, respectively. Desorption of adsorbed Cr(VI) and regeneration of the MSM were successfully achieved by NaOH and HCl treatments to deprotonate and protonate the amine groups, respectively. By selecting a silane with suitable functional groups, the surface properties may be tailored for a particular pollutant.

Lanthanum (hydr)oxide-based materials are attractive as highly efficient adsorbents for phosphate removal from both sewage and lake environment. However, dissolved organic carbon (DOC) coexists in the waters and exact information is still lacking on how DOC influence the phosphate adsorption process. In this study, competitive adsorption of phosphate and DOC on lanthanum modified zeolite (LMZ) was investigated using humic acid as the representative. In LMZ, lanthanum hydroxide was shown to be the active ingredient accounting for >98% of the binding sites of both phosphate and DOC. Without competition, the maximum adsorption capacity of phosphate and DOC estimated from the Langmuir isotherm model was 52.25 and 41.32 mg/g, respectively. When coexisted, DOC did not affect the adsorption of phosphate while phosphate reduced the adsorption of DOC by ~40%. In addition, preloading LMZ with DOC had little effect on phosphate adsorption while coating with phosphate substantially lowered DOC adsorption. Furthermore, phosphate can release most of the adsorbed DOC (>60%), while DOC can not replace adsorbed phosphate (<2%). The adsorption kinetics of both phosphate and DOC was best described by the psudo-second-order model (r2 > 0.999). The adsorption of both phosphate and DOC increased with decreasing pH or increasing ionic strength. We proposed that phosphate was competitive than DOC for the ligand exchange sites of singly-coordinated hydroxyls, but DOC can be solely adsorbed onto the uncharged hydroxyls via hydrogen bonding.

The removal of phosphate from source-separated urine is an efficient approach to reduce the P-load in receiving waters due to its high P concentration and low volume in wastewater. However, a highly efficient adsorbent is imperative for this purpose. Metal-organic frameworks (MOFs) have recently attracted a lot of attention in adsorption due to their outstanding physicochemical features. In this study, we examined four Zr-based MOFs (UiO-66, UiO-66-NO2, UiO-66-Br and UiO-66-NH2) for the adsorption of phosphate from acidified urine. Our results indicated that the zirconium content, pore size and crystallinity are driving forces for the adsorption process. UiO-66-NH2 displayed the highest adsorption capacity (153.9 mg/g) at 25 degrees C and pH 4. Phosphate in urine could be nearly totally depleted ( > 99% removal) using UiO-66-NH2 at a dosage >= 13.5 g/L. Elevating temperature and lowering pH are effective strategies to enhance the adsorption performance. The reduction of the isoelectric point of UiO-66-NH2 after P uptake, the activation energy of the adsorption process estimated using Arrhenius equation (63.1 kJ/mol), FTIR spectroscopy and XPS suggested that inner-sphere complexation between phosphate and Zr atoms in the MOFs was the key adsorption mechanism. The performance of adsorption-desorption-regeneration using real human urine was verified.