Enhanced removal of ammonia nitrogen from rare earth wastewater by NaCl modified vermiculite: Performance and mechanism

Biomimetic flame retardant adhesive via combining polysiloxane, chitosan and vermiculite nanosheets inspired by nacre and arthropod cuticle

The wood industry's dependence on traditional petrochemical adhesives, which pose environmental and health risks, has spurred research into sustainable alternatives. Sustainable bio-based polysaccharide materials show promise due to their inherent adhesive properties, despite challenges related to mechanical weaknesses and water resistance. Inspired by the hardening mechanisms of nacre and arthropod cuticles, we have developed a novel biomimetic flame-retardant HPA/OCTS/VMT NSs-NH2 adhesive. This adhesive uses oxidized chitosan (OCTS) to crosslink with hyperbranched polymers (HPA) and surface-modified vermiculite nanosheets ((VMT NSs-NH2), conferring flame retardancy. Furthermore, the interfacial compatibility between the VMT NSs-NH₂ nanomaterials and the adhesive is enhanced through the mediating action of HPA, thereby promoting the homogeneous dispersion of the adhesive. Through Schiff base chemistry-mediated covalent crosslinking, VMT NSs-NH2 integrates with OCTS, forming a microphase-separated structure similar to marine arthropod cuticles. This combination yields a wood bonding strength of 1.7 MPa, a limiting oxygen index of 36.7 %, and excellent cone calorimetry test results, providing an environmentally friendly adhesive solution for the wood industry.

Multidimensional effects of green waste vermicomposting on cadmium contaminated soil ecosystems: From physicochemical properties to microbial communities

Soil heavy metal pollution and green waste accumulation have emerged as two major environmental challenges, necessitating the development of sustainable remediation and management technologies. This study investigated the remediation effects of vermicomposted green waste (JE) on cadmium (Cd)-polluted soil. Batch adsorption tests and soil microcosm experiments were conducted to examine the impact of JE on soil quality, microbial community structure, and Cd biotransformation. Results demonstrated that, compared with untreated green waste, JE significantly increased the Cd2+ adsorption capacity by 55.94 %. This enhancement was attributed primarily to increased surface functional groups and altered crystal structure through vermicomposting. JE treatment effectively improved the soil physicochemical properties, increased the nutrient content and elemental exchangeability, and increased soil enzyme activities. At the microbial level, JE drove the assembly and modification of soil microbial communities, increasing their diversity and abundance, particularly those of beneficial bacterial groups. Environmental matrix analysis revealed complex interactions among soil properties, enzyme activities, and soil microbial communities in terms of Cd biotransformation. Overall, vermicomposted green waste rapidly improved the Cd adsorption efficiency and, upon its soil application, effectively enhanced the Cd-polluted soil quality while optimizing soil microbial community structure and function. This ultimately led to Cd immobilization and inert transformation in the soil. This study provides a solid theoretical and practical foundation for the safe utilization and sustainable remediation of heavy metal-polluted agricultural soils, as well as the resource utilization of green waste.

Evaluation of the bactericidal activity of plasma-activated NaCl solution (PAN) against foodborne pathogens: Inactivation mechanism and application to mackerel

The objective of this study was to assess the bactericidal effect of plasma-activated NaCl solution (PAN) against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes and apply PAN as a brine salting solution for mackerel. To enhance the bactericidal effect of plasma-activated water (PAW), NaCl solutions (0, 3.5, 7, and 10%) were treated with plasma for 20 and 40 min to generate PAN. Plasma-activated glycerol solution (PAG) was also included to evaluate the influence of water activity on plasma activation and its effect on microbial activity. Physicochemical analysis revealed that elevating the NaCl concentration of PAN led to a decrease in pH, an increase in oxidation-reduction potential, and higher levels of reactive species such as H2O2 and HOCl. PAN showed greater antibacterial activity compared to PAW and PAG, except for L. monocytogenes, where 40 min activation time and treatment time exceeding 20 min was required for significantly higher reduction to occur. PAN exhibited greater antibacterial activity at higher NaCl concentrations, which was attributed to increased ionic strength and reactive chlorine species. Additionally, we evaluated the microbial mechanisms of PAN by assessing cellular damage and alterations. The common observation across the three pathogens was that PAN resulted in increased cell membrane damage, reduced intermembrane enzyme activity, higher intracellular ROS levels, and changes in zeta potential values, while DNA damage was observed only in PAN-treated L. monocytogenes. Furthermore, when PAW and PAN were stored for up to four weeks, PAN showed higher efficacy compared to PAW. 10% PAN was also effective against foodborne pathogens on mackerel, achieving log reductions of 3.62 for E. coli O157:H7, 4.62 for S. Typhimurium, and 3.18 for L. monocytogenes after a 20 min treatment without adversely affecting quality. Our results demonstrated the antibacterial activity and action mechanism of PAN, presenting its potential application in the seafood industry.

Copper supported Dowex50WX8 resin utilized for the elimination of ammonia and its sustainable application for the degradation of dyes in wastewater

To obtain high efficient elimination of ammonia (NH4+) from wastewater, Cu(II), Ni(II), and Co(II)) were loaded on Dowex-50WX8 resin (D-H) and studied their removal efficiency towards NH4+ from aqueous solutions. The adsorption capacity of Cu(II)-loaded on D-H (D-Cu2+) towards NH4+ (qe = 95.58 mg/g) was the highest one compared with that of D-Ni2+ (qe = 57.29 mg/g) and D-Co2+ (qe = 43.43 mg/g). Detailed studies focused on the removal of NH4+ utilizing D-Cu2+ were accomplished under various experimental conditions. The pseudo-second-order kinetic model fitted well the adsorption data of NH4+ on D-Cu2+. The non-linear Langmuir model was the best model for the adsorption process, producing a maximum equilibrium adsorption capacity (qmax = 280.9 mg/g) at pH = 8.4, and 303 K in less than 20 min. The adsorption of NH4+ onto D-Cu2+ was an exothermic and spontaneous process. In a sustainable step, the resulting D-Cu(II)-ammine composite from the NH4+ adsorption process displayed excellent catalytic activity for the degradation of aniline blue (AB) and methyl violet 2B (MV 2B) dyes utilizing H2O2 as an eco-friendly oxidant.

Rapid enrichment of AnAOB with a novel vermiculite/tourmaline modification technology for enhanced DEAMOX process

The DEnitrifying AMmonium OXidation (DEAMOX) has been proven to be a promising process treating contaminated surface water containing ammonia and nitrate, while the enrichment of the slow-growing anammox bacteria (AnAOB) remains a challenge. In this study, a novel polyurethane-adhesion vermiculite/tourmaline (VTP) modified carrier was developed to achieve effective enrichment of AnAOB. The results demonstrated that the VTP-1 (vermiculite: tourmaline = 1:1) system exhibited the greatest performance with the total nitrogen removal efficiency reaching 87.6% and anammox contributing 63% to nitrogen removal. Scanning electron microscope analysis revealed the superior biofilm structure of the VTP-1 carrier, providing attachment for AnAOB. The addition of VTP-1 promoted the secretion of EPS (extracellular polymeric substances) by microorganisms, which increased to 85.34 mg/g VSS, contributing to the aggregation of anammox cells. The favorable substrate microenvironment created by NH4+ adsorption and NO2- supply via partial denitrification process facilitated the growth of AnAOB. The relative abundance of Candidatus Brocadia and Thauera increased from 0.04% to 0.3%-1.03% and 2.06% in the VTP-1 system, respectively. This study sheds new light on the anammox biofilm formation and provides a valid approach to initiate the DEAMOX process for low nitrogen polluted water treatment.

Study on adsorption of ammonia nitrogen by sodium-modified kaolin at calcination temperature

Natural kaolin (NK) is not used as a material for removal of ammonia nitrogen in wastewater because of its low ammonia adsorption capacity. In this study, sodium-modified kaolin adsorbent (NaCK) with high ammonia nitrogen adsorption capacity was prepared by NaOH modification of calcined NK, which was developed to address this problem. The adsorption properties were evaluated by batch static adsorption test. The results showed that when the initial concentration of ammonia nitrogen was 10 mg/L, pH = 8, and dosage of adsorbent was 1 g/L, the adsorption capacity of NaCK-600 for ammonia nitrogen was the best, reaching 6.23 mg/g, which was 34.6 times higher than that of NK (0.18 mg/g). Batch static adsorption test combined with adsorption kinetics, adsorption isothermal, and characteristic data showed that NaCK prepared at different temperatures had different adsorption mechanisms. Batch static adsorption test data of NaCK-600 was in good agreement with the pseudo-second-order model and Langmuir model, and the main mechanism of its adsorption of ammonia nitrogen was the ion exchange of NH4+ and Na+ in NaCK. After the third cycle, the removal rate of NaCK-600 was still up to 76.44%, which indicates that NaCK-600 has considerable potential for removal of ammonia nitrogen in wastewater and provides a new way for the application of kaolin in removal of ammonia nitrogen.

A passive sink-zeolite permeable reactive barrier to control NH4+-N pollution plume within groundwater: Conceptual design and numerical modeling

Ammonium nitrogen (NH₄⁺-N) is a typical inorganic pollutant in the groundwater at landfill sites, and high-concentration NH₄⁺-N is toxic to humans and organisms. Zeolite can effectively remove NH₄⁺-N in water by adsorption, and it is suitable to be used as a type of reactive materials for permeable reactive barriers (PRBs). A passive sink-zeolite PRB (PS-zPRB) with higher capture efficiency than a continuous permeable reactive barrier (C-PRB) was proposed. And a passive sink configuration was integrated with PRB in the PS-zPRB, this configuration enabled the high hydraulic gradient of groundwater at the treated sites to be fully utilized. In order to explore treatment efficiency for groundwater NH₄⁺-N using the PS-zPRB, numerical modeling on decontamination of NH₄⁺-N plumes at a landfill site was performed. The results indicated that the NH₄⁺-N concentrations of PRB effluent gradually decreased from 21.0 mg/L to 0.5 mg/L within 5 y, and met the drinking water standards after treatment for 900 d. The decontamination efficiency index of PS-zPRB was consistently higher than 95% within 5 y, and the service life of PS-zPRB would be over 5 y. The capture width of PS-zPRB effectively exceeded the PRB length by around 50%. Compared with C-PRB, the capture efficiency of PS-zPRB was increased by around 28%, and the reactive material of PS-zPRB was saved by approximately 23% in volume.

An Eco-Friendly Adsorbent Based on Bacterial Cellulose and Vermiculite Composite for Efficient Removal of Methylene Blue and Sulfanilamide

In this work, a novel composite of bacterial cellulose (BC) and expanded vermiculite (EVMT) composite was used to adsorb dyes and antibiotics. The pure BC and BC/EVMT composite were characterized using SEM, FTIR, XRD, XPS and TGA. The BC/EVMT composite exhibited a microporous structure, providing abundant adsorption sites for target pollutants. The adsorption performance of the BC/EVMT composite was investigated for the removal of methylene blue (MB) and sulfanilamide (SA) from an aqueous solution. The adsorption capacity of BC/ENVMT for MB increased with increasing pH, while the adsorption capacity for SA decreased with increasing pH. The equilibrium data were analyzed using the Langmuir and Freundlich isotherms. As a result, the adsorption of MB and SA by the BC/EVMT composite was found to follow the Langmuir isotherm well, indicating a monolayer adsorption process on a homogeneous surface. The maximum adsorption capacity of the BC/EVMT composite was found to be 92.16 mg/g for MB and 71.53 mg/g for SA, respectively. The adsorption kinetics of both MB and SA on the BC/EVMT composite showed significant characteristics of a pseudo-second-order model. Considering the low cost and high efficiency of BC/EVMT, it is expected to be a promising adsorbent for the removal of dyes and antibiotics from wastewater. Thus, it can serve as a valuable tool in sewage treatment to improve water quality and reduce environmental pollution.