Passivation of soil heavy metals using environmental materials is an important method or important in situ remediation measure. There are more studies on inorganic environmental materials for heavy metal passivation, but not enough studies on organic and their composite environmental materials with inorganic ones. In order to reveal the passivation effect of coal-based ammoniated humic acid (CAHA), biochemical humic acid (BHA), biochar (BC) and other organic types and inorganic environmental materials such as zeolites (ZL) on soil heavy metals and their biological effectiveness. The microstructures of these materials were analyzed by Scanning electron microscope (SEM). The main components of the environmental materials were analyzed by Energy dispersive spectrometer (EDS), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction spectrum (XRD) to elucidate the mechanism of passivation of heavy metals in soil by these environmental materials. The study was conducted to investigate the effects of different types of environmental materials and their combinations on the passivation effect and biological effectiveness of Pb and Cd complex contamination in soil by means of soil incubation and pot experiments using single-factor and multifactor multilevel orthogonal experimental designs. Soil incubation experiments proved that the effective state of soil Pb and Cd in T₇ was reduced by 13.40% and 11.07%, respectively. The extreme difference analysis determined the optimized formulation of soil lead and cadmium passivation as BHA: CAHA: BC: ZL = 3.5:5:20:10. The pot experiment proved that the application of composite environmental materials led to the reduction of lead and cadmium content and increase of biomass of Pak-choi, and the optimal dosage of optimized composite environmental materials was 23.1 g/kg.

Removal of multi-ionic contaminants from water resources has been a major challenge faced during the treatment of water for drinking and industrial applications. In the present study, varying composition of magnesium doped hydroxyapatite (Mg-HAp) and zeolite nanocomposite embedded porous polymeric beads were synthesized using solvent displacement method and its sorption efficiency towards multi-ion contaminant (such as Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, Tl, Th, U, V and Zn) was investigated in aqueous solution and spiked groundwater. The prepared beads were characterized using suitable techniques like high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) equation. The surface area and pore radius of the beads varied from 6.996 to 66.469 m²/g and 1.698–3.960 nm respectively according to the composition of the bead. The control bead without nanocomposite showed maximum surface area. Multi-ion adsorptions onto beads were confirmed using an inductively coupled plasma-optical emission spectrophotometer (ICP-OES) and X-ray photoelectron spectrophotometer (XPS). The sorption efficiency was high at pH 5 owing to its anionic surface charge leading to an increase in affinity towards the cations. For validating field application, selected high performance beads were tested in multi-ion spiked groundwater. The results indicated that the Mg-HAp nanocomposite bead dominate all the other bead compositions with more than 90% removal efficiency for most of the multi-ion contaminants. The feasible adsorption mechanism has been discussed. This adsorption study revealed that the Mg-HAp nanocomposite bead is a promising material that is cost-effective, non-toxic, biodegradable, eco-friendly and highly efficient towards the removal of multi-ionic contaminants from groundwater.

Additives are considered a promising approach to accelerate the composting process and alleviate the dissemination of pollutants to the environment. However, nearly all previous articles have focused on the impact of additive amounts on the reduction of HMs, which may not fully represent the main factor shaping HMs bioavailability status during composting. Simultaneously, previous reviews only explored the impacts, speciation, and toxicity mechanism of HMs during composting. Hence, a global-scale meta-analysis was conducted to investigate the response patterns of HMs bioavailability and compost parameters to different additives, composting duration, and composting factors (additive types, feedstock, bulking agents, and composting methods) by measuring the weighted mean values of the response ratio "[ln (RR)]" and size effect (%). The results revealed that additives significantly lessened HMs bioavailability by ≥ 40% in the final compost products than controls. The bioavailability decline rates were −40%, −60%, −57%, −55%, −42%, and −44% for Zn, Pb, Ni, Cu, Cr, and Cd. Simultaneously, additives significantly improved the total nitrogen (TN) (+16%), pH (+5%), and temperature (+5%), and decreased total organic carbon (TOC) (−17%), moisture content (MC) (−18%), and C/N ratio (−19%). Furthermore, we found that the prolongation of composting time significantly promoted the effect of additives on declining HMs bioavailability (p < 0.05). Nevertheless, increasing additive amounts revealed an insignificant impact on decreasing the HMs bioavailability (p > 0.05). Eventually, using zeolite as an additive, chicken manure as feedstock, sawdust as a bulking agent, and a reactor as composting method had the most significant reduction effect on HMs bioavailability (p < 0.05). The findings of this meta-analysis may contribute to the selection, modification, and application of additives and composting factors to manage the level of bioavailable HMs in the compost products.

Catalytic pyrolysis is a promising chemical recycling technology to supplement mechanical recycling since plastics can be broken down into monomers or converted to the required fuels and chemicals. In this study, a microwave (MW) -responsive SiC foam@zeoltie core-shell structured catalyst was proposed for the catalytic pyrolysis of polyolefins. Under microwave irradiation, the SiC foam core works as both microwave adsorber and catalyst support, thus concentrating the generated heat energy on the ZSM-5 zeolite shell, where the catalytic reaction takes place. SiC foam with an open cellular structure can also improve the global transport of mass and heat during plastics pyrolysis. In this work, the effects of the SiO₂/Al₂O₃ ratio and alkaline treatment of ZSM-5 zeolite coated SiC foam under MW irradiation on the variations in product distribution from low-density polyethylene (LDPE) pyrolysis were investigated at 450 °C. The results indicated that the appropriate acidity and pore structure were crucial to upgrading gas and liquid products. Particularly, the creation of a mesoporous structure in ZSM-5 zeolite via alkaline treatment could improve the diffusion of large molecules and products, thus significantly increasing the selectivity of high-valued light olefins and aromatics while inhibiting the formation of unwanted alkanes, which are expected in the chemical industry. Concretely, the concentration of olefins in gas increased to 51.0 vol% for ZSM-5(50)-0.25AT, and 65.6 vol% for ZSM-5 (50)-0.50AT, compared with 45.2 vol% for the parent ZSM-5(50). The relative concentration of aromatics in liquid decreased from 96.6% for ZSM-5(50) to 75.9% for ZSM-5(50)-0.25AT, and 71.1% for ZSM-5(50)-0.50AT. Given the respective yield of gas and liquid, the total selectivity of C2–C4 olefins and aromatics for mesoporous ZSM-5 zeolites could reach 58.6–64.9% during LDPE pyrolysis, which were higher than that for the parent ZSM-5 zeolite.

Iron-based materials have been widely investigated because of their high surface reactivity, which has shown potential for the remediation of metal(loid)s in groundwater. However, the disadvantages of structural stability and economic feasibility always limit their application in permeable reactive barrier (PRB) technology. In this study, zeolite-supported iron particles (Zeo-Fe) were synthesized by an innovative low-cost physical preparation method that is suitable for mass production. The removal efficiency and mechanism of typical metal(loid)s (Pb²⁺, Cd²⁺, Cr⁶⁺ and As³⁺) were subsequently investigated using various kinetic and equilibrium models and characterization methods. The results of scanning electron microscopy and energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) confirmed that zero valent iron (Fe⁰) and oxidation product (Fe₃O₄) were successfully loaded and efficiently dispersed on zeolite. The synthesized Zeo-Fe exhibited excellent adsorption and redox capacities for the cations Pb²⁺, Cd²⁺ and anions Cr⁶⁺, As³⁺. The increase in the pH resulting from Fe⁰ corrosion also enhanced the precipitation of Fe-metal(loid)s. The maximum removal capacity for Pb²⁺, Cd²⁺, Cr⁶⁺ and As³⁺ was up to 70.00, 9.12, 2.35 and 0.36 mg/g, respectively. The removal processes were well described by the pseudo-second-order kinetic model for Pb²⁺ and Cd²⁺, Lagergren pseudo first-order kinetics model for As³⁺ and double phase first order kinetics model l for Cr⁶⁺. Cr⁶⁺ was rapidly reduced to Cr³⁺ by the Fe⁰ stabilized on Zeo-Fe, and the oxidation of As³⁺ to As⁵⁺ was attributed to the Fe⁰/Fe²⁺ oxidation process at the interface over time, which was further demonstrated by the mineral phase and element valence analyses of reacted Zeo-Fe. The removal mechanism for metal(loid)s was a combination of physical and chemical processes, including adsorption, co-precipitation and reduction-oxidation. Conclusively, Zeo-Fe has been shown to have potential as an effective and economical material for removing various metal(loid)s used in PRB.

The recovery and recycling of nutrients (N&P) from wastewater are one of the major topics to save primary energy and resources, to raise the efficiency of wastewater treatment plants, and to foster a future circular economy. In the present study, the removal of ammonium (NH₄⁺) and phosphate (PO₄³⁻) using natural and Ca-treated zeolite is investigated in detail. Special emphasis is put on the simultaneous removal of both species from model solutions followed by elaborate mineralogical analyses (XRD, EPMA, FEG-SEM) for zeolite characterization and in order to determine the type, structure, and crystal sizes of CaP-phases precipitating on the zeolites surface. The effectivity of the phosphate segregation and chemical composition and the crystalline structure of the CaP-phase precipitating on the surface of the zeolite depend on the physico chemical conditions in particular on pH, molar ratio of Ca and P (due to zeolite modification), and the presence of NH₄⁺. Results of simultaneous removal experiments of N&P revealed that Ca pretreatment enhances P segregation and increases the obtainable P-loadings of Ca–zeolites. Maximum P-loadings of 25 mg g⁻¹ Ca–zeolite in binary solutions containing both ammonium and phosphate were obtained. Simultaneous phosphate removal by surface precipitation of CaP-phases does not significantly influence ammonium ion exchange and the type of CaP-precipitates formed on the zeolite surface is assumed to be mainly brushite and apatite.

Spent bleaching earth (SBE) as an industrious solid rubbish seriously causes the environmental pollution problem. The resourceful utilization of SBE has become increasingly important. In this work, silicon and carbon ingredients derived from SBE were coincidently employed to synthesize a 4A zeolite/carbon composite molecular sieve (4A/CMS). Therein, the graphite carbon components in the form of porous lamellar scattering among the interlayer, surface, and periphery of 4A zeolite promote the rate of mass transfer for the lipophilic gas, which can effectively improve the adsorption property for the volatile organic compounds. The obtained 4A/CMS has large specific surface area, hierarchical pore structure, satisfactory adsorption capacity, and regeneration performance, and its equilibrium adsorption capacity of p-xylene can achieve 209.57 mg·g⁻¹. The pseudo-first-order rate equation is appropriate for the adsorption kinetics. In the end, the formation mechanism of 4A/CMS was illuminated in detail. □ Spent bleaching earth (SBE) as an industrious solid rubbish were utilized resourcefully. Silicon and carbon ingredients from SBE were coincidently employed to synthesize 4A/CMS. Graphitic carbon with hierarchical pore promoted the rate of mass transfer of organic gas. 4A/CMS exhibited excellent adsorption capacity and regeneration performance of p-xylene.

The selection and configuration of soil media are a core issue of the bioretention system. A porous carbon material of Fe₃O₄/biochar (BSF) was prepared by adding pickling wastewater to modified sludge biochar, which could serve as a good adsorption performance and cheap media for bioretention system. Through the analytic hierarchy process (AHP), different media were evaluated according to their characteristics. By comparing the characteristics of BSF to bio-ceramic (BC), zeolite (ZE), and activated carbon (AC), it was found that BSF has a larger specific surface area and pore volume. The hydrological characteristics of the medium were also tested. The results show that BSF has better water-absorbing quality and hydraulic conductivity than the other three media, but the water-retention property of the medium seems to be inferior. BSF has stable adsorption performance for ammonia nitrogen (NH₄⁺-N) and total phosphorus (TP) in rainwater. Its high adsorption capacity is maintained at 5–35°C, but it is very susceptible to pH factors. The adsorption process by BSF and other media conforms to pseudo-second-order kinetics and the Langmuir model in rainwater. In general, the performance of BSF is shown to be superior to BC, ZE, and AC, making it a potential medium for bioretention system.

Organic and inorganic mixtures can be developed as immobilizing agents that could reduce heavy metal accumulation in crops and contribute to food safety. Here, inorganic materials (lime, L; zeolite, Z; and sepiolite, S) and organic materials (biochar, B, and compost, C) were selectively mixed to produce six composite soil amendments (LZBC, LSBC, LZC, LZB, LSC, and LSB). Given the fact that LZBC showed the best performance in decreasing soil Cd availability in the incubation experiment, it was further applied in the field condition with 14 vegetables as the test crops to investigate its effects on crop safety production in polluted greenhouse. The results showed that LZBC addition elevated rhizosphere soil pH by 0.1–2.0 units and reduced soil Cd availability by 1.85–37.99%. Both the biomass and the yields of edible parts of all vegetables were improved by LZBC addition. However, LZBC addition differently affected Cd accumulation in edible parts of the experimental vegetables, with the observation that Cd contents were significantly reduced in Allium fistulosum L., Amaranthus tricolor L., and Coriandrum sativum Linn., but increased in the three species of Lactuca sativa. Further health risk assessment showed that LZBC application significantly decreased daily intake of metal (DIM), health risk index (HRI), and target hazard quotient (THQ) for Cd in Allium fistulosum L., Amaranthus tricolor L., and Coriandrum sativum Linn., whereas increased all the indexes in Lactuca sativa. Our results showed that the effect of a composite amendment on Cd accumulation in different vegetables could be divergent and species-dependent, which suggested that it is essential to conduct a pre-experiment to verify applicable species for a specific soil amendment designed for heavy metal immobilization.

In this research work, the removal of chromium(III) ion (Cr³⁺) by raw materials such as zeolite (Z) and chert (CH) was investigated. The batch method was invested, using two concentrations in chromium(III) sulphate at 21.31mg/L and at 22mg/L in nitrate nonahydrate. In order to improve the porous structure, the specific surface area and the adsorbent capacity of these natural materials, a purification technique was undertaken, namely a chemical treatment of the used natural materials (zeolite and cherts) with NaCl was carried out. Thus, the obtained raw and purified materials were characterized through chemical analysis by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and liquid nitrogen adsorption-desorption analyses by measuring the specific surface area (BET method). The results demonstrated that zeolite (Z) and chert (CH) are good adsorbents and that the purified materials have a potential adsorbent to reduce the chromium concentration for a maximum adsorbed amount (Qads) of about 2.72mg/g and 2.85mg/g, respectively for purified zeolite and chert (Z-p and CH-p) in chromium(III) nitrate and about 2.83mg/g and 2.48mg/g, respectively for purified zeolite and chert (Z-p and CH-p) in chromium(III) sulphate. These results revealed that natural zeolite and chert hold great potential to remove cationic heavy metal species from industrial wastewater. The kinetics adsorption was also examined using pseudo-first-order and pseudo-second-order kinetics models. The adsorption kinetics was best described by the pseudo-second-order.