Metal Ions Removal Using Nano Oxide Pyrolox™ Material

Isolation and screening of phosphorus solubilizing bacteria from saline alkali soil and their potential for Pb pollution remediation

The high pH and salinity of saline alkali soil not only seriously restrict the growth of crops, but also aggravate the pollution of heavy metals. The fixation of heavy metals and the regulation of pH by phosphorus solubilizing microorganisms may become a new way to repair heavy mental and improve saline alkali soil. In this study, a saline-alkali resistant bacteria (CZ-B1, CGMCC No: 1.19458) was screened from saline-alkali soil, and its tolerance to salt/alkali/lead stress was investigated by shaking flask experiment. The strain was identified as Bacillus amyloliquefaciens by morphology and 16S rRNA gene sequence analysis. The optimum growth temperature of CZ-B1 is about 35°C-40℃. The maximum salt stress and pH that it can tolerance are 100 g/L and 9 respectively, and its tolerance to Pb²⁺ can reach 2000 mg/L. The phosphorus release amount of CZ-B1 to Ca₃(PO₄)₂ within 72 h is 91.00-102.73 mg/L. The phosphate solubilizing index in PVK agar medium and NBRIP agar medium are more than 2, which can be defined as phosphate solubilizing bacteria. Moreover, the dissolution of CZ-B1 to phosphorus is mainly attributed to tartaric acid, citric acid and succinic acid in inorganic medium. In addition, the removal rate of Pb²⁺ by CZ-B1 can reach 90.38% for 500 mg/L. This study found that CZ-B1 can immobilize Pb through three biological mechanisms (organic acid, extracellular polymers and mineralization reaction). The release of succinic acid (10.97 g/L) and citric acid (5.26 g/L) may be the main mechanism to promote the mineralization reaction of CZ-B1 (phosphate and oxalate) and resistance to Pb stress. In addition, the high enrichment of Pb²⁺ by EPS can increase the rate of extracellular electron transfer and accelerate the mineralization of CZ-B1. The screening and domestication of saline-tolerant phosphorus-solubilizing bacteria not only help to remediate Pb contamination in saline soils, but also can provide P element for plant growth in saline soil.

Resource Recycling Utilization of Distillers Grains for Preparing Cationic Quaternary Ammonium—Ammonium Material and Adsorption of Acid Yellow 11

Using distillers grains (DG) as raw material after pre-treatment with sodium hydroxide (NaOH) and modified with cationic etherification agent 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC), cationic quaternary ammonium distillers grains adsorption material (CDG) was successfully prepared. The optimal adsorption conditions were an adsorption temperature of 25 °C, adsorption time of 180 min, amount of adsorbent at 8.5 g/L, initial dye concentration of 100 mg/L, and pH of dye solution 7.0. The structure of CDG was characterized by FTIR, EDS, SEM, BET, ultraviolet spectrum analysis, and analysis of the zeta potential, while the adsorption mechanism was studied by adsorption kinetics, isotherms, and thermodynamics. The results showed that CHPTAC modified the distillers grains successfully and induced the formation of CDG with a large number of pore structures and good adsorption effect. The highest adsorption yield was above 98%, while after eight rounds of adsorption–desorption experiments, the adsorption rate was 81.80%. The adsorption mechanism showed that the adsorption process of acid yellow 11 (AY11) by CDG conforms to the pseudo-second-order kinetic model, mainly with chemical and physical adsorption such as pore adsorption and electrostatic adsorption. Thermodynamics conforms to the Freundlich isothermal model, and the adsorption process is a spontaneous, endothermic and entropy-increasing process.

Heavy Metal Pollution and Potential Ecological Risk Assessment in a Typical Mariculture Area in Western Guangdong

The distribution characteristics, environmental contamination states, and potential ecological risks of chromium (Cr), copper (Cu), arsenic (As), lead (Pb), and cadmium (Cd) in seawater, sediment and breeding feed were studied in a typical mariculture area in western Guangdong of China. Pearson correlation analysis was used to determine metal homology, and the single-factor index, potential ecological risk index, hazard quotient (HQ), and joint probability curve (JPC) were used to evaluate pollution states and ecological risk of metals. Four main statements can be concluded from the results: (1) Pb and Cu showed a similar distribution pattern in the seawater and sediment and their contents in the breeding wastewater exceeded the standard limits in several stations. (2) Cr, Cu, and As have similar sources in the feeds, which may be an important source of metals in water. (3) The risk assessment revealed that the sediment from the studied areas was at a low ecological risk of heavy metal, whereas, water in the pond and outfall was slightly polluted by Pb, and water in the cages and outfall were slightly polluted by Cu. (4) Both the hazard quotient (HQ) and joint probability curve showed the overall risk probabilities (ORPs) in the waters ranked as Cu > Cr > Pb > Cd > As. Although Pb and Cd had HQ values greater than 1, their ORPs were acceptable. This study highlights that multiple evaluation models are more reliable than the single ecological risk assessment for evaluating heavy metal pollution risks in the mariculture area.

Role of plant growth promoting rhizobacteria in the alleviation of lead toxicity to Pisum sativum L

Plant-microbe interaction is a significant tool to tackle heavy metals problem in the soil. A pot trial was conducted to evaluate the efficiency of lead tolerant rhizobacteria in improving pea growth under Pb stress. Lead sulfate (PbSO4) was used for spiking (250, 500, and 750 mg kg-1). Results indicated that inoculation with Pb-tolerant PGPR strain not only alleviated the harmful impacts of Pb on plant growth but also immobilized it in the soil. PGPR in the presence of Pb at concentrations of 0, 250, 500 and 750 mg kg-1, increased shoot and root lengths by 21, 15, 18% and 72, 80, 84%, respectively, than uninoculated control. Moreover, fresh biomass of shoots and roots were also increased by 51, 45, 35% and 57, 101, 139% respectively, at Pb concentrations of 250, 500 and 750 mg kg-1. In addition, PGPR inoculation also reduced Pb concentration in the roots and shoots by 57, 55, 49% and 70, 56 and 58% respectively, than uninoculated control. So, PGPR proved to be an efficient option for reducing Pb mobility and can be effectively used for its phytostabilization. Novelty statementLead (Pb) is highly noxious and second most toxic element in the nature having high persistence. It ranks 1st in the priority list of hazardous substances and causes adverse effects after its entry into the living system. So, its remediation is inevitable. Plant growth promoting rhizobacteria (PGPR) possess the potential to not only survive under stressed environments, but also promote plant growth on account of their different plant growth promoting mechanisms.Most researchers have worked on its bioaccumulation in plant body. This study however, used pea as a test crop and caused Pb phytostabilization and thereby, suppressed its entry in the above-ground plant parts.

Coupling of Anodic Oxidation and Soil Remediation Processes: A Review

In recent years, due to industrial modernization and agricultural mechanization, several environmental consequences have been observed, which make sustainable development difficult. Soil, as an important component of ecosystem and a key resource for the survival of human and animals, has been under constant contamination from different human activities. Contaminated soils and sites require remediation not only because of the hazardous threat it possess to the environment but also due to the shortage of fresh land for both agriculture and urbanization. Combined or coupled remediation technologies are one of the efficient processes for the treatment of contaminated soils. In these technologies, two or more soil remediation techniques are applied simultaneously or sequentially, in which one technique complements the other, making the treatment very efficient. Coupling anodic oxidation (AO) and soil remediation for the treatment of soil contaminated with organics has been studied via two configurations: (i) soil remediation, ex situ AO, where AO is used as a post-treatment stage for the treatment of effluents from soil remediation process and (ii) soil remediation, in situ AO, where both processes are applied simultaneously. The former is the most widely investigated configuration of the combined processes, while the latter is less common due to the greater diffusion dependency of AO as an electrode process. In this review, the concept of soil washing (SW)/soil flushing (SF) and electrokinetic as soil remediation techniques are briefly explained followed by a discussion of different configurations of combined AO and soil remediation.

Toxicity, migration and transformation characteristics of lead in soil-plant system: Effect of lead species

Lead (Pb) is a typical hazardous element of high concern in species characteristics involving toxicity, migration and transformation. A greenhouse experiment was conducted using Solanum nigrum L. grown in soils treated by divalent (Pb²⁺), tetravalent (Pb⁴⁺), trimethyl (TML) and triethyl (TEL) lead for 60 days. Results of physio-biochemical parameters indicated Pb toxicity was ranked as TEL > TML > Pb²⁺ > Pb⁴⁺ in a dose-dependent manner, and the correlation levels of organic species were higher than inorganic species. S. nigrum L. adopted phytostabilization strategy through fixing Pb in roots and restricting its transfer to shoots. More phytotoxic Pb was absorbed from soils treated by Pb²⁺ than Pb⁴⁺ as well as TEL than TML. In soils, inorganic Pb species were mainly present in residues while organic Pb species in Fe/Mn oxide and exchangeable fractions. Although most of Pb species in plant existed in the low-bioavailable extractions of 1 M NaCl and 2% HAC, the water-soluble Pb extracted by d-H₂O and 80 % ethanol were increased to a large extent under high-level exposure. The occurrence of reduction and (de)alkylation were considered as the major pathways in the biotransformation of Pb species. This study will conduce to the ecological risk management for Pb-contaminated soils.

Preparation of Activated Carbon from Coffee Waste as an Adsorbent for the Removal of Chromium (III) from Water. Optimization for an Experimental Box-Behnken Design

Coffee grounds are an organic waste consisting of the ground, roasted and processed grain for the extraction of coffee, being of great volume the waste obtained, which, if not treated and preserved for a long time, emanates unpleasant aromas and becomes an optimal means for the proliferation of flies, and other pests. Activated carbon has the characteristic of being a material that has a large surface area; because of this, it is used in adsorption, which refers to the retention of atoms, ions, and molecules on its surface. In this paper, the production of activated carbon is presented by means of the physicochemical activation of coffee waste by calcining at 900 °C and subsequent activation with sulfuric acid, as well as the Box–Behnken design of three factors for chromium (III) adsorption optimization. It is determined that the optimal conditions for performing the adsorption are pH = 3 and a contact time of 140 min. According to the analysis of variance for the experimental design, it is determined that the initial chromium formation is not significant for the adsorption process. Under the optimal adsorb conditions of 96%, an application is given to the erasure of coffee for the production of activated carbon, which serves as the adsorbent agent applied to the removal of chromium (III) aqueous. The area of activated carbon obtained is 13657.89 ± 251.09 m2/g determined by the acetic acid adsorption isotherm method.

Removal of Hazardous Oxyanions from the Environment Using Metal-Oxide-Based Materials

Scientific development has increased the awareness of water pollutant forms and has reawakened the need for its effective purification. Oxyanions are created by a variety of redox-sensitive metals and metalloids. These species are harmful to living matter due to their toxicity, nondegradibility, and mobility in aquatic environments. Among a variety of water treatment techniques, adsorption is one of the simplest, cheapest, and most effective. Since metal-oxide-based adsorbents poses a variety of functional groups onto their surface, they were widely applied in ions sorption. In this paper adsorption of harmful oxyanions by metal oxide-based materials according to literature survey was studied. Characteristic of oxyanions originating from As, V, B, W and Mo, their probable adsorption mechanisms and comparison of their sorption affinity for metal-oxide-based materials such as iron oxides, aluminum oxides, titanium dioxide, manganium dioxide, and various oxide minerals and their combinations are presented in this paper.

Metal–organic framework-based materials for the recovery of uranium from aqueous solutions

This review focuses on the recent progress in MOFs and MOF-based materials as superior adsorbents for the efficient removal of uranium from aqueous solutions.

Imidazole-2yl-Phosphonic Acid Derivative Grafted onto Mesoporous Silica Surface as a Novel Highly Effective Sorbent for Uranium(VI) Ion Extraction

A new imidazol-2yl-phosphonic acid/mesoporous silica sorbent (ImP(O)(OH)₂/SiO₂) was developed and applied for uranium(VI) ion removal from aqueous solutions. The synthesized material was characterized by fast kinetics and an extra-high adsorption capacity with respect to uranium. The highest adsorption efficiency of U(VI) ions was obtained for the reaction system at pH 4 and exceeded 618 mg/g. The uranium(VI) sorption proceeds quickly in the first step within 60 min of the adsorbent sites and ion interactions. Moreover, the equilibrium time was determined to be 120 min. The equilibrium and kinetic characteristics of the uranium(VI) ions uptake by synthesized sorbent was found to follow the Langmuir-Freundlich isotherm model and pseudo-second-order kinetics rather than the Langmuir, Dubinin-Radushkevich, and Temkin models and pseudo-first-order or intraparticle diffusion sorption kinetics. The adsorption mechanism for uranium on the sorbent was clarified basing on the X-ray photoelectron spectroscopy (XPS) analysis. The model of UO₂²⁺ binding to surface of the sorbent was proposed according to the results of XPS, i.e., a 1:1 U-to-P ratio in the sorbed complex was established. The regeneration study confirms the ImP(O)(OH)₂/SiO₂ sorbent can be reused. A total of 45% of uranium ions was determined as originating from the sorbent leaching in the acidic solutions, whereas when the basic solutions were used, the removal efficiency was 12%.