Adsorption of brilliant green dye onto activated carbon prepared from cashew nut shell by KOH activation: Studies on equilibrium isotherm

Activated carbon from cashew nut shell via a potassium hydroxide (KOH) at 600 °C in an N₂ atmosphere and their characteristics using FT-IR, XRD, SEM with EDS, and BET analysis was investigated. The cashew nut shell activated carbon obtained by KOH activation with a CNS/KOH ratio of 1:1 at 600 °C (N₂ atmosphere) for 2 h had the highest surface area (407.80 m²/g) as compared to other ratio samples. Amongst, CNS/KOH ratios of 1:1 sample are used for the adsorbent, they are effects of contact time, pH, adsorbent dose, and initial dye concentration on brilliant green (BG) removal efficiency were studied. Moreover, the Langmuir and Freundlich adsorption models consisted utilized to affirm the adsorption isotherms. They are, best fitting for BG experimental equilibrium data was achieved with the Langmuir isotherm, giving a maximum BG adsorption capacity of 243.90 mg/g.

Ball milling potassium ferrate activated biochar for efficient chromium and tetracycline decontamination: Insights into activation and adsorption mechanisms

Herein, novel Fe-biochar composites (MBC_BM500 and MBC_BM700) were synthesized through K₂FeO₄ co-pyrolysis and ball milling, and were used to eliminate Cr(VI)/TC from water. Characterization results revealed that higher temperature promoted formation of zero-valent iron and Fe₃C on MBC_BM700 through carbothermal reduction between K₂FeO₄ and biochar. The higher specific surface area and smaller particle size of MBC_BM500/700 stemmed from the corrosive functions of K and the ball milling process. And the maximal uptake amount of MBC_BM700 for Cr(VI)/TC was 117.49/90.31 mg/g, relatively higher than that of MBC_BM500 (93.86/84.15 mg/g). Furthermore, ion exchange, pore filling, precipitation, complexation, reduction and electrostatic attraction were proved to facilitate the adsorption of Cr(VI), while hydrogen bonding force, pore filling, complexation and π-π stacking were the primary pathways to eliminate TC. This study provide a reasonable design of Fe-carbon materials for Cr(VI)/TC contained water remediation, which required neither extra modifiers nor complex preparation process.

Nanoporous Carbon from Oil Palm Leaves via Hydrothermal Carbonization-Combined KOH Activation for Paraquat Removal

In this study, nano-porous carbon was completely obtained from oil palm leaves (OPL) by hydrothermal pretreatment with chemical activation, using potassium hydroxide (KOH) as an activating agent. Potassium hydroxide was varied, with different ratios of 1:0.25, 1:1, and 1:4 (C: KOH; w/w) during activation. The physical morphology of nano-porous carbon has a spongy, sponge-like structure indicating an increase in specific surface area and porosity with the increasing amount of KOH activating agent. The highest specific surface area of OPL nano-porous carbon is approximately 1685 m²·g^-1, with a total pore volume of 0.907 cm³·g^-1. Moreover, the OPL nano-porous carbon significantly showed a mesoporous structure designed specifically to remove water pollutants. The adsorptive behavior of OPL nano-porous carbon was quantified by using paraquat as the target pollutant. The equilibrium analyzes were explained by the Langmuir model isotherm and pseudo-second-order kinetics. The maximum efficiency of paraquat removal in wastewater was 79%, at a paraquat concentration of 400 mg·L^-1, for 10 min in the adsorption experiment. The results of this work demonstrated the practical application of nano-porous carbon derived from oil palm leaves as an alternative adsorbent for removing paraquat and other organic matter in wastewater.

Potassium ferrate followed by alkali-stripping treatment to achieve short-chain fatty acids and nitrogen recovery from waste activated sludge

Waste activated sludge (WAS) is a potential resource to achieve carbon-neutral goal of wastewater treatment plant. However, the solubilization is always the rate-limiting step for resource recovery from anaerobic digestion of WAS. This study reported a novel strategy, i.e., potassium ferrate (PF) followed by alkali-stripping treatment, to achieve short-chain fatty acids (SCFAs) and nitrogen recovery from WAS. Results showed that whether the stripping process was conducted under alkaline condition or not, the SCFAs production potential was increased rather than reduced. The promoted SCFAs production was due to the accelerated solubilization and hydrolysis stages but the inhibited methanogenesis stage. The SCFAs yield reached 258 mg chemical oxygen demand (COD)/g volatile suspended solids (VSS), and the carbon source, including SCFAs, soluble polysaccharides and proteins, reached 384 mg COD/g VSS. The potentially recovered nitrogen was about 8.71 mg NH₄⁺-N/g VSS. This work may provide some new solutions for enhancing resource recovery from WAS.

Potassium ferrate combined with ultrafiltration for treating secondary effluent: Efficient removal of antibiotic resistance genes and membrane fouling alleviation

Antibiotic resistance genes (ARGs) are considered as emerging environmental contaminants, which should be controlled by wastewater treatment plants to prevent their discharge into the environment. However, conventional treatment techniques generally fail to successfully reduce ARGs, and the release of cell-free ARGs was underestimated. In this study, potassium ferrate (Fe(VI)) pretreatment combined with ultrafiltration (UF) process was developed to remove both cell-associated and cell-free ARGs in real secondary effluent, compared to ferric chloride (Fe(III)) and poly-aluminum chloride (PACl) pretreatment processes. It was found that total ARGs especially cell-free ARGs were effectively removed by Fe(VI) oxidation. However, due to the poor settleability of the negatively charged particles formed by Fe(VI) in the secondary effluent, the removal of cell-associated ARGs was less compared to Fe(III) and PACl pretreatments. The combination of Fe(VI) and UF removed the most ARGs (3.26 - 5.01 logs) due to the efficient removal of cell-free ARGs by Fe(VI) (> 2.15 logs) and co-interception of both cell-associated ARGs and Fe(VI) formed particles of the UF. High-throughput sequencing revealed that Fe(VI) decreased the viability and relative abundances of the potential ARGs hosts. Fe(VI)-UF exhibited the best performance on humic-like fluorescent organic matters removal, as well as the least phytotoxicity in the effluent. Moreover, membrane fouling was remarkably alleviated by Fe(VI) pretreatment because (1) Fe(VI) removed macromolecules such as protein-like and polysaccharide-like substances which would block the membrane pores, (2) Fe(VI) improved the hydrophilicity of foulants and reduced the hydrophobic adsorption between foulants and membrane. In short, Fe(VI)-UF is a promising technology to efficiently remove ARGs (especially cell-free ARGs) and alleviate UF membrane fouling in wastewater reclamation.

Degradation of ofloxacin by potassium ferrate: kinetics and degradation pathways

Drug residues, including various antibiotics, are being increasingly detected in aqueous environments. Ofloxacin (OFX) is one such antibiotic that is widely used in the treatment of several bacterial infections; however, chronic exposure to this antibiotic can have adverse impacts on human health. Hence, the identification of an effective OFX degradation method is essential. Thus, in this study, the degradation performance of OFX using potassium ferrate (Fe(VI)) under the influence of different initial concentrations, pH, temperature, and common ions in water was investigated. OFX degradation by Fe(VI) was directly proportional to the concentration of Fe(VI) and temperature and inversely proportional to the pH. Among the common ions in water, Fe³⁺ and NH₄⁺ could significantly promote the degradation of OFX by Fe(IV), while humic acid (HA) significantly inhibited it. Under the conditions of [Fe(VI)]:[OFX] = 15:1, T = 25℃, and pH = 7.0, the removal efficiency of 8 μM OFX reached more than 90% in 4 min. Seven intermediates were identified by quadrupole time-of-flight tandem ultra-performance liquid chromatography mass spectrometry (Q-TOF LC/MS), and two possible pathways for the degradation of OFX by Fe(VI) were proposed. Overall, the results suggest that advanced oxidation technology using Fe(VI) is effective for treating wastewater containing OFX.

Simultaneous recovery of vivianite and produce short-chain fatty acids from waste activated sludge using potassium ferrate as pre-oxidation treatment

Recovery resources from waste active sludge (WAS) is an effective way to alleviate the predicament of WAS disposal, and it is also conducive to the carbon neutralization of wastewater treatment systems. This study discussed the strategy of WAS anaerobic fermentation after pre-oxidation with potassium ferrate (K₂FeO₄, PF), which can simultaneously recover vivianite and enhance SCFAs production. The results showed that PF pre-oxidation considerably shortened the fermentation time of SCFAs to 2 days, and the main Fe-P mineral was vivianite. The optimal PF dosage of 0.06 g Fe (VI)/g TSS for pre-oxidation WAS resulted in the maximum SCFAs production and vivianite recovery rate of 3698.2 ± 118.98 mg COD/g VSS and 32.39%, respectively. The mechanism analysis showed that the oxidizing properties of PF significantly accelerated the disintegration of tight EPS, release of protein and sludge acidification efficiency. Moreover, the PF strengthened the transfer of P to the solid phase, forming the Fe-P mineral and unsaturated coordination state of phosphate group. Then the key microorganism Geobacter reduced the Fe³⁺ in Fe-P state to Fe²⁺ and combined unsaturated phosphate to form vivianite. This study provides an alternative method for resource recovery and environmentally friendly disposal of WAS and contributes to the carbon neutrality of urban water systems.

Nanoplastics interaction with feldspar and weathering originated secondary minerals (kaolinite and gibbsite) in the riverine environment

Despite the massive accumulation of nanoplastics (NPs) in the freshwater system, research so far has highly focused on the marine environment. NPs interaction with mineral surfaces can influence their fate in freshwater, which will further impact their bioavailability and transport to the oceans. Current work focuses on understanding NPs interaction with weathering sequence of minerals in freshwater under varying geochemical conditions. Primary mineral feldspar and weathering originated secondary minerals, i.e., kaolinite and gibbsite, were investigated for interaction with NPs under batch mode under relevant environmental conditions. Minerals-NPs interaction was also investigated in natural water samples. Results showed that the amorphous nature, small particle size, and positive surface charge of gibbsite resulted in multi-fold sorption of NPs (108.1 mg/g) compared to feldspar (7.7 mg/g) and kaolinite (11.9 mg/g). FTIR spectroscopy revealed hydrogen bonding and complexation as major players in gibbsite-NPs interaction suggesting the possibility of their co-precipitation. The continuous adsorption-desorption and limited sorption capacity of feldspar and kaolinite can be attributed to their negative surface charge, larger size, crystalline nature, and physical sorption. Therefore, both minerals may co-transport and enhance the mobility of NPs.

Preparation of magnesium Ferrite-Doped magnetic biochar using potassium ferrate and seawater mineral at low temperature for removal of cationic pollutants

Magnetic biochar has captured a great interest for remediation of environment as an easily separable carbonous adsorbent. Herein, a highly adsorptive magnetic biochar was manufactured through seawater mineral and K₂FeO₄ co-promoted pyrolysis of jackfruit peel at 300 °C for removal of different cationic pollutants, and characterized by element analysis, FTIR, SEM-EDS, XRD, XPS and so on. MgFe₂O₄ was generated without external base and a 19.42 emu/g saturation magnetization was achieved. Simultaneously, iron oxides and oxygen containing groups were introduced. The magnetic biochar exhibited 61.30 mg/g, 129.61 mg/g, and 1238.30 mg/g adsorption capacities for Cu²⁺, methylene blue (MB), and malachite green (MG) at 25 °C, respectively, and remarkably surpassed the corresponding pristine biochar. The adsorption of MB and MG was mainly realized by electrostatic interaction, hydrogen bonding, complexation, and π-π electron-donor-acceptor interaction, and that of Cu²⁺ was attributed to electrostatic interaction, hydrogen bonding, and complexation.

Effect of potassium persulphate addition on sludge disintegration of a mesophilic anaerobic fermentation system

Persulphates, an advanced oxidation process, has been recently used as an alternative pretreatment method to enhance short-chain fatty acids (SCFAs) yield from waste-activated sludge (WAS) anaerobic fermentation (AF). But so far, the effects of peroxydisulphate (PDS) dosages on mesophilic anaerobic fermentation are still not studied fully. Herein, we explored the influences of potassium PDS addition on mesophilic AF of WAS. Notably, the addition of PDS could drastically accelerate WAS solubilization and hydrolysis, which was proportional to the amount of PDS. The maximal total SCFAs yield of 249.14 mg chemical oxygen demand/L was obtained with 120 mg PDS/g suspended solids addition at 6 days of AF, which was 2.2-fold that of the control one. Tightly bound extracellular polymeric substances (EPSs) were transformed into loosely bound EPS and dissolved organic matters, and aromatic proteins and humic-like substances of EPSs were disintegrated, which were caused by the devastating effects of PDS treatments on EPSs disruption. The intracellular constituents of microbial cells in the sludge were released accordingly. As a result, there was release of soluble substrates derived from the disintegration of both EPSs and cells, the amounts of which were proportional to the dose of PDS. Moreover, microbial diversity and richness were both decreased in the presence of PDS, and the relative abundance of phyla Actinobacteria increased with the increase of the PDS dosage. In addition, the stability of sludge flocs was destroyed in the presence of PDS, the distribution of particle size tended to be small and dispersive, and dewaterability of the sludge was deteriorated.

An efficient, green and sustainable potassium hydroxide activated magnetic corn cob biochar for imidacloprid removal

The extensive use of imidacloprid (IMI) has led to its being frequently detected in natural water, also caused the potential damage to the ecosystem. Development of efficient, green and sustainable technique is demanded to eliminate this problem. A novel biochar (KMCBC) derived from agriculture waste of corn cob was first time co-modified by potassium hydroxide (KOH), ferric chloride (FeCl₃) and zinc chloride (ZnCl₂), which showed the greater adsorption amount (410 mg g^-1 at 298 K) for imidacloprid (IMI). Pseudo-second-order kinetic and Langmuir isotherm models fitted well with the experimental data, together with the physicochemical characterization analysis, demonstrating that the adsorption process of IMI by KMCBC might be mainly controlled by micropore filling, π-π electron donor-acceptor and functional groups interactions (H-bonding and complexation). Additionally, the thermodynamics parameters suggested that IMI adsorption in this study was a spontaneous, endothermic and randomly increasing process. Besides, KMCBC owned the easy separation performance and promising environmental safety, also exhibited a high selective adsorption capacity regardless of solution pH (its optimum adsorption performance for IMI was obtained at pH = 5), inorganic ions strength and humic acid (HA) concentrations. The regenerated KMCBC (synergistic ultrasound/ethanol) could sustainably and efficiently adsorb IMI in the reuse cycles. Therefore, this study provided an efficient, green and sustainable adsorbent of KMCBC for IMI removal.

The effect of KOH activation and Ag nanoparticle incorporation on rice husk-based porous materials for wastewater treatment

Major agricultural solid waste, rice husk (RH)-based mesoporous materials were prepared by potassium hydroxide (KOH) treatment of RH and RH hydrochar (RHH) produced at 180 °C with 20 min reaction time. In this study, RH was treated with three different methods: RH activation by KOH (KOH-RH), RH activation by KOH-aqueous silver (Ag)-shell nanoparticle (AgNP) incorporation followed calcination at 550 °C for 2 h (AgNP-KOH-RH) and hydrothermally carbonized RH activation by KOH (KOH-RHH). The main objective of this study was to determine the effect of KOH activation with different synthesis approaches and compare the characterization results of RH based porous material to identify the potential adsorbent application for wastewater treatment. Therefore, after activation in different methods, all interactive properties such as elemental, chemical, structural, morphological, and thermal analyses were investigated comprehensively for all samples. The crystallinity peak intensity around 22°λ at the angle of diffraction of 2θ confirmed the presence of silica, higher stability of the material, and removal of organic components during the KOH activation. AgNP-KOH-RH and KOH-RHH presented high porosity on the outer surface. The presence of negligible volatile matter in KOH-RHH by TGA demonstrated the decomposition of organic compound. Very high ratio of aromatic carbon and lignin content by FTIR and XPS analysis in both AgNP-KOH-RH and KOH-RHH showed these two samples have improved stability. Very high negative surface charge (zeta potential) in AgNP-KOH-RH (-43.9 mV) and KOH-RHH (-43.1 mV) indicated the enhanced water holding capacity. Surface area for all experimented porous materials has been enhanced after KOH activation, where KOH-RHH demonstrated the maximum surface area value, 27.87 m²/g. However, AgNP-KOH-RH presented maximum pore diameter, 18.16 nm, and pore volume, 0.12 cm³/g. Hence, it can be concluded that both KOH-RHH and AgNP-KOH-RH have the potential to be implemented as wastewater adsorbents.

Antifungal and defense elicitor activity of Potassium phosphite against fungal blast disease on ptxD-OE transgenic indica rice and its acceptor parent

In rice farming, the blast disease caused by Magnaporthe oryzae (T.T. Hebert) M.E. Barr. is one of the primary production constraints worldwide. The current blast management options such as blast-resistant varieties and spraying fungicides are neither durable nor commercially and environmentally compatible. In the present study, we investigated the antifungal and defense elicitor activity of potassium phosphite (Phi) against M. oryzae on elite rice cultivar BPT5204 (popularly known as Samba Mahsuri in India) and its transgenic rice variant (ptxD-OE) over-expressing a phosphite dehydrogenase enzyme. The Phi was evaluated both preventively and curatively on rice genotypes where the preventive spray of Phi outperformed the Phi curative application with significant reductions in both rice blast severity (35.67-60.49%) and incidence (22.27-53.25%). Moreover, the application of Phi increased the levels of photosynthetic pigments (Chlorophyll and Carotenoids) coupled with increased activity of defense enzymes (PAL, SOD, and APx). Besides, Phi application also induced the expression of defense-associated genes (OsCEBiP and OsPDF2.2) in the rice leaf. Furthermore, the Phi application reduced the reactive Malondialdehyde (lipid peroxidation) to minimize the cellular damage incited by Magnaporthe in rice. Overall, the present study showed the potential of Phi for blast suppression on rice as an alternative to the current excessive use of toxic fungicides.

Evaluation of potassium ferrate activated biochar for the simultaneous adsorption of copper and sulfadiazine: Competitive versus synergistic

Combined pollution caused by organic pollutants and heavy metals pose a significant challenge to the adsorption process. In this study, iron-modified biochar (Fe-BC) was prepared by using ferrate (K₂FeO₄) and wheat stalk as the precursors for the adsorption of copper (Cu²⁺) and sulfadiazine (SDZ), especially under combined pollution scenarios. Iron modification not only enlarged the surface area but also loaded iron oxide nanoparticles on biochar surface. Accordingly, Fe-BC exhibited better adsorption capability of Cu²⁺ and SDZ than the pristine biochar (BC). The corresponding maximum adsorption capacities of Fe-BC₇₀₀ were 46.85 mg g^-1 and 45.43 mg g^-1 towards Cu²⁺ and SDZ, respectively. Interestingly, the adsorption was elevated in binary-pollutants system, suggesting a synergistic effect, which was probably attributed to the mutual bridging effects and complexation between Cu²⁺ and SDZ. The loaded iron oxide particles could serve as a physical barrier to separate the adsorptions of Cu²⁺ and SDZ and thus inhibited the competitive adsorption. Meanwhile, theoretical calculation demonstrated that sulfonamide group was the most probable binding site. Columns packed with Fe-BC₇₀₀ showed better performances for Cu²⁺ and SDZ removal in binary system (635.73 BV for Cu²⁺ and 4846.26 BV for SDZ) than in single systems (571.60 BV for Cu²⁺ and 3572.06 BV for SDZ), which was consistent with batch adsorption experiments. These results demonstrated the potential application of Fe-BC₇₀₀ for simultaneous adsorption of Cu²⁺ and SDZ and provided a cost-effective way for the remediation of organic and inorganic pollutants.

Isolation and Identification of Penicillium rubens from the Local Strain in Mosul, Iraq, and Investigation of Potassium Phosphate Effect on its Growth

Penicillium species is one of the most common microscopic filamentous fungi that have been isolated from widespread substrates. In this study, soil samples from different areas of Mosul, Iraq, were examined by morphological and molecular methods. Fungi were isolated and grown in diagnostic culture media, including Czapek Yeast Extract Agar, Malt Extract Agar, and 25% Glycerol nitrate agar at different temperatures of 15, 20, 25, and 30°C. The growth rate of the fungus was also evaluated in the culture containing K₂HPO₄. In the molecular method, the obtained fragment was sequenced using the Internal Transcribed Spacer region primers after replication. Morphological evaluation of both macroscopic and microscopic features revealed that strains were Penicillium rubens, and molecular methods used have confirmed the isolated strain. The results of this study showed a decrease in the diameters of the colonies at different growth temperatures when doubling the amount of K₂HPO₄. In addition, the findings revealed that compared to growth inhibition in the control groups, the maximum growth inhibition was 16 and 29 mm on Czapek Dox Agar (modified) medium at incubation temperatures of 20°C and 25°C, respectively. As a result, K₂HPO₄ has an important role in inhibiting growth; therefore, it can be used as Fungicide.

Effectiveness of potassium ferrate (VI) as a green agent in the treatment and disinfection of carwash wastewater

Carwash wastewater treatment with potassium ferrate (VI) (K₂FeO₄) was optimized by response surface methodology. The optimum conditions for chemical oxygen demand removal were established a pH 3.5, 0.328 g/L dose of K₂FeO₄, and with a process duration of 48 min. At these conditions, chemical oxygen demand, total organic carbon, total nitrogen, and total phosphorus decreased by 70.3, 58.9, 73.3, 82.0%, respectively; and the putrid odor was reduced. Simultaneously, the total viable count, total coli count, most probable number of fecal enterococci, and the total proteolytic bacteria count decreased by 89.5, 93.1, 92.9, and 95.0 %, respectively. Comparatively, an application of 0.450 g/L FeCl₃·6H₂O corresponding to the iron content in 0.328 g/L of K₂FeO₄ resulted in a decrease of total viable count, total coli count, most probable number of fecal enterococci and the total proteolytic bacteria count only by 38.1, 31.2, 42.9, and 58.0%, respectively. Therefore, flocculation with polyacrylamide anionic flocculant combined with potassium ferrate (VI) oxidation is a more effective alternative to coagulation with FeCl₃ and the same flocculant. The use of potassium ferrate (VI) is a viable option for the treatment of carwash wastewater.

Potassium Phosphite Enhances the Antagonistic Capability of Bacillus amyloliquefaciens to Manage Tomato Bacterial Wilt

Bacterial wilt caused by Ralstonia solanacearum is a distributed and worldwide soilborne disease. The application of biocontrol microbes or agricultural chemicals has been widely used to manage tomato bacterial wilt. However, whether and how agricultural chemicals affect the antagonistic ability of biocontrol microbes is still unknown. Here, we combined potassium phosphite (K-Phite), an environmentally friendly agricultural chemical, and the biocontrol agent Bacillus amyloliquefaciens QPF8 (strain F8) to manage tomato bacterial wilt disease. First, K-Phite at a concentration of 0.05% (wt/vol) could significantly inhibit the growth of R. solanacearum. Second, 0.05% K-Phite enhanced the antagonistic capability of B. amyloliquefaciens F8. Third, the greenhouse soil experiments showed that the control efficiency for tomato bacterial wilt in the combined treatment was significantly higher than that of the application of B. amyloliquefaciens F8 or K-Phite alone. Overall, our results highlighted a novel strategy for the control of tomato bacterial wilt disease via application and revealed a new integrated pattern depending on the enhancement of the antagonistic capability of biocontrol microbes by K-Phite.

Coeffect of pyrolysis temperature and potassium phosphate impregnation on characteristics, stability, and adsorption mechanism of phosphorus-enriched biochar

Potassium phosphate (K₃PO₄)-impregnated bamboo was pyrolyzed at temperatures ranging from 350 to 950 °C to explore the coeffect of pyrolysis temperature and K₃PO₄ impregnation on biochar's characteristics and adsorption behavior. The degree of aromatization and graphitization in phosphorus-enriched biochars (PRBCs) rose as temperature increased, whereas H/C and O/C ratios, pH value, and O-containing group content decreased. The pre-aging impact of K₃PO₄ impregnation results in increased stability and adsorption performance of PRBCs. Adsorption mechanism of PRBCs to heavy metal varies from pyrolysis temperature. Micropores dominate medium-temperature PRBCs (prepared at 550 ∼ 750 °C), possessing the highest P-containing group content (116 % that of PRBC-350) and maximal adsorption capacity (greater than289 mg/g). The medium-temperature PRBCs adsorb Cd (II) via the role of O-containing groups, PO₄^3-, and P₂O₇^4-, mainly by reactions of organic complexation, precipitation and inorganic complexation, respectively. 550 °C is the optimal pyrolysis temperature for both energy saving and heavy metal adsorption.

Hydrothermally-altered feldspar reduces metal toxicity and promotes plant growth in highly metal-contaminated soils

Novel green technologies for soil remediation have been focusing on altering soil properties and improving soil health. Hydrothermally-altered feldspar (HYP, HydroPotash), recently developed, is being related as both an efficient amendment to immobilize heavy metals in soils and a plant nutrients source, consisting in a promising technology for revegetation of contaminated sites. In order to evaluate the effectiveness of using HYP for phytostabilization programs, two different soils (Technosol and Oxisol) collected from a smelting site were amended with increasing doses of HYPs (HYP-1 and HYP-2): 15, 30, 60, and 120 Mg ha^-1. For comparison, a control (soil without amendment) and a soil amended with zeolite (clinoptilolite) were also included as treatments. After 90 days of incubation, HYPs decreased up to 83.8 % of Cd availability and reduced exchangeable Al up to 100 %. HydroPotash increased pH, cation exchange capacity, and contents of potassium, calcium, and phosphorus, as well as microbial biomass carbon, and fluorescein diacetate hydrolysis of soils. Andropogon gayanus, Eucalyptus grandis, and Heterocondylus vitalbae started growing from the dose of 15 Mg ha^-1 HYPs in the Oxisol and 60 Mg ha^-1 HYPs in the Technosol. Principal component analysis indicates that plant shoot dry weight was negatively correlated with extractable Cd and Zn and positively with pH, CEC, and Ca content. Besides promoting plant growth, HYPs reduced heavy metals (Cd and Zn) absorption by plants, indicating that HYP has potential use as an amendment in phytostabilization programs.

Microwave-assisted catalytic hydrothermal carbonization of Laminaria japonica for hydrochars catalyzed and activated by potassium compounds

There are limited investigations describing preparation and application of alga-based hydrochars via microwave-assisted catalytic hydrothermal carbonization (MA-CHTC). Therefore, hydrochars were successfully prepared from macroalgae biomass Laminaria japonica impregnated with KH2PO4, KCl, K2CO3, and KOH as acidic, neutral salt, and alkaline catalysts, respectively, via the MA-CHTC. Comprehensive characterization of physicochemical properties of the hydrochars, including yields, elemental and phase composition, specific surface areas, functional groups, and morphology, confirmed different catalytic effects of these catalysts on hydrochar formation. Adsorption kinetics and isotherms of Pb(II) revealed significant improvement of adsorption capacities for Pb(II) due to synergetic chemical activation of the spiked catalysts. Therefore, the synergetic catalytic effects and chemical activation is benefic for tailored design of engineered hydrochars with different properties for special application through selection of catalysts during the MA-CHTC process.

Enhanced methane production from waste activated sludge by potassium ferrate combined with ultrasound pretreatment

This study explored the effect of potassium ferrate (PF) combined with ultrasound (US) pretreatment on methane generation from sludge by a series of experiments and simulations. Batch experiments showed that the pretreatment of PF coupled with US exhibited positively synergy on the methane yield. And by the pretreatment of 0.05 g/g TSS (total suspended solids) PF cooperated with US (1 W/mL, 25 kHz, 15 min), the methane yield was enhanced from 180.62 ± 3.26 to 228.83 ± 4.76 mL/g VSS (volatile suspended solids). Mechanism studies confirmed that the co-pretreatment of PF and US efficiently promoted sludge disintegration, and the biodegradability of sludge organics was obviously enhanced. Microbial community analysis showed that the functional microorganisms participating in sludge anaerobic digestion were enriched by PF cooperated with US pretreatment, with the total abundance enhanced from 12.96% in the control to 17.96% in PF + US pretreated reactor.

Using potassium ferrate control hazardous disinfection by-products during chlorination

The generation of hazardous disinfection by-product is one of the major problems in drinking water chlorination. This study aims to investigate the potential of potassium ferrate (K₂FeO₄) on by-product control. Filtered raw water from a water treatment plant in Jinan was used to evaluate the effects of K₂FeO₄ dose, pH, ammonia nitrogen, and Br^- concentration on trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP). The results present that 3 mg/L K₂FeO₄ effectively reduced ultraviolet absorbance at 254 nm (UV₂₅₄) by 45%, but removed little dissolved organic carbon (DOC) by 12% at pH 7.40, since K₂FeO₄ tends to attack the electron-rich part of organic matter molecules but with restricted mineralization ability. Fluorescence excitation-emission matrix (EEM) analyses indicate the effective removal of fulvic acid and humic acid. Increasing K₂FeO₄ dose reduced THMFP but increased HAAFP, due to their precursors reacting with K₂FeO₄ in different pathway, while the rising pH or Br^- concentration increased THMFP but decreased HAAFP. Both THMFP and HAAFP decrease with increasing ammonia nitrogen concentrations. Additionally, it was found that under alkaline conditions, trihalomethanes (THMs) were dominated by haloacetic acids (HAAs).

KNbO3/ZnO heterojunction harvesting ultrasonic mechanical energy and solar energy to efficiently degrade methyl orange

In this paper, KNbO₃/ZnO nanocomposite was synthesized and used in piezo/photocatalytic degradation of methyl orange (MO) under simulated sunlight and ultrasonic vibration. Under simulated solar light, the optimal KNbO₃/ZnO sample presented a MO degradation rate of 0.047 min^-1, which is 2.47 times higher than that of ZnO. The promotion effect of KNbO₃ on ZnO was also observed in the piezoelectric catalytic reaction. In addition, the co-utilization of solar and mechanical energy can further increase the MO degradation rate. Piezoelectric property and photoresponse capability are the origins of the piezo/photo catalytic behavior of the KNbO₃/ZnO composite. Owing to the different band potentials of KNbO₃ and ZnO, the electric potential field at their interface can drive the second distribution of the photo/piezoinduced charge carriers and hence promote the photo/piezocatalytic activity. This phenomenon was verified by the analysis on transient photocurrent and piezocurrent response. Trapping experiments on reactive species were also conducted. Superoxide radicals, holes, and hydroxyl radicals were found to be the main reactive species during the photo/piezocatalytic reaction. Recycling test showed that the KNbO₃/ZnO composite exhibited good catalytic stability during six consecutive uses. Given its advantages of good catalytic activity and stability, the synthesized KNbO₃/ZnO nanocomposite material has great potential in the further use of solar and mechanical energy to develop new water purification technologies.

Clinical and Radiographic Assessments of Potassium Nitrate in Polycarboxylate Versus Mineral Trioxide Aggregate as Pulpotomy Biomaterials in Immature Mandibular First Permanent Molars: A Randomized Clinical Trial

INTRODUCTION

The purpose of this study was to compare clinically and radiographically the effects of potassium nitrate in polycarboxylate cement and mineral trioxide aggregate (MTA) as pulpotomy agents in vital immature mandibular first molars.

METHODS

The trial design was a parallel randomized, 1:1 allocation ratio, with both the participants and the data assessor blinded. A total of 50 molars of 48 eligible children aged 6-9 years were studied. The children had mandibular immature first molars with extensive caries that revealed pulp exposure during caries excavation. Patients were randomly allocated equally into 2 groups in which potassium nitrate in polycarboxylate cement (the intervention group) and MTA (the control group) were used as pulpotomy biomaterials. The treated teeth were restored permanently. The primary outcome was clinical/radiographic assessment after 1 week, 6 months, and 12 months. The secondary outcomes were radiometric analysis at 6 and 12 months to determine dimensional changes during maturogenesis. The digital radiographs were imported to image processing software to perform radiometric measurements. Data were tabulated and statistically analyzed with significance set at P ≤ .05.

RESULTS

Only a single tooth failed at the 6-month recall, and another one was lost during recall in each group. Thus, the overall success rate for cases/group who finally attended the 12-month follow-up time point was 92% (23/25) with no statistically significant difference between the 2 groups. At the 12-month recall, successful cases showed root development with an increase in root length and a decrease in apical foramen width. Complete apical closure was observed in 65.2% of the roots in the intervention group and 52.1% in the control group.

CONCLUSIONS

The clinical and radiographic success reported in the present study reveals that potassium nitrate in polycarboxylate cement could be used as a biological and economic alternative to MTA as a pulpotomy agent in vital immature mandibular first molars. Further follow-up for longer periods is recommended.

Potassium hydroxide-modified algae-based biochar for the removal of sulfamethoxazole: Sorption performance and mechanisms

Biochar has been deemed one of the most promising sorbents for the removal of organic pollutants from aqueous solution. In this study, potassium hydroxide-modified Enteromorpha prolifera biochars (PEBCs) were prepared for the first time and applied for efficient sorption of a typical antibiotic, sulfamethoxazole (SMX). The characteristics of PEBCs, including morphology, pore structure, graphitization degree, surface functional groups, and surface element composition, were investigated. Moreover, sorption kinetic and isotherm experiments were carried out to explore the sorption process, performance, and mechanisms. The maximum sorption capacity for SMX can reach 744 mg g^-1, which is much higher than that reported for sorbents. The sorption of SMX onto PEBCs was controlled by both physical and chemical processes. Moreover, pore filling, hydrogen bonding, partitioning, π-π stacking, and electrostatic interactions were possible sorption mechanisms. This study indicated that the structure and properties of algal biochar can be further improved by potassium hydroxide modification at high temperature and applied as an excellent sorbent for the removal of antibiotics from aqueous solution.