Removal of Different Kinds of Heavy Metals by Novel PPG-nZVI Beads and Their Application in Simulated Stormwater Infiltration Facility

Sources, effects and present perspectives of heavy metals contamination: Soil, plants and human food chain

Heavy metal (HM) poisoning of agricultural soils poses a serious risk to plant life, human health, and global food supply. When HM levels in agricultural soils get to dangerous levels, it harms crop health and yield. Chromium (Cr), arsenic (As), nickel (Ni), cadmium (Cd), lead (Pb), mercury (Hg), zinc (Zn), and copper (Cu) are the main heavy metals. The environment contains these metals in varying degrees, such as in soil, food, water, and even the air. These substances damage plants and alter soil characteristics, which lowers crop yield. Crop types, growing circumstances, elemental toxicity, developmental stage, soil physical and chemical properties, and the presence and bioavailability of heavy metals (HMs) in the soil solution are some of the factors affecting the amount of HM toxicity in crops. By interfering with the normal structure and function of cellular components, HMs can impede various metabolic and developmental processes. Humans are exposed to numerous serious diseases by consuming these affected plant products. Exposure to certain metals can harm the kidneys, brain, intestines, lungs, liver, and other organs of the human body. This review assesses (1) contamination of heavy metals in soils through different sources, like anthropogenic and natural; (2) the effect on microorganisms and the chemical and physical properties of soil; (3) the effect on plants as well as crop production; and (4) entering the food chain and associated hazards to human health. Lastly, we identified certain research gaps and suggested further study. If people want to feel safe in their surroundings, there needs to be stringent regulation of the release of heavy metals into the environment.

Simultaneous removal of phenanthrene and Pb using novel PPG-CNTs-nZVI beads

PPG-CNTs-nZVI bead was synthesized by polyvinyl alcohol, pumice, carbon nanotube, and guar gum-nanoscale zero-valent iron to be applied on simultaneously removal of polycyclic aromatic hydrocarbons (PAHs; phenanthrene) and heavy metals (Pb2+) via adsorption. The individual and simultaneous removal efficiency of phenanthrene and Pb2+ using the PPG-CNTs-nZVI beads was evaluated with a range of initial concentrations of these two pollutants. The kinetics and isotherms of phenanthrene and Pb2+ adsorption by the PPG-CNTs-nZVI beads were also determined. The PPG-CNTs-nZVI beads show reasonably high phenanthrene adsorption capacities (up to 0.16 mg/g), and they absorbed 85% of the phenanthrene (initial concentration 0.5 mg/L) in 30 min. High Pb2+ adsorption capabilities were also demonstrated by the PPG-CNTs-nZVI beads (up to 11.6 mg/g). The adsorption fits the Langmuir model better than the Freundlich model. The adsorption still remained stable with various ionic strength circumstances and a wide pH range (2-5). Additionally, the co-adsorption of phenanthrene and Pb2+ by the PPG-CNTs-nZVI beads resulted in synergistic effects. Particularly, phenanthrene-Pb2+ complex formation via π-cation interactions demonstrated a greater affinity than phenanthrene or Pb2+ alone. The present findings suggest that PPG-CNTs-nZVI beads may be effective sorbents for the simultaneous removal of PAHs and heavy metals from contaminated waters.

Influence of tomato waste composts on dry matter and heavy metals content in cucumber and summer squash seedlings

Huge quantities of agricultural waste are available annually in Saudi Arabia, which are not well exploited, leading to large environmental pollution and health problems. The use of different proportions of tomato waste compost (TWC) mixed with commercial peat-moss as a natural, economical, cheap and environmentally friendly fertilizer for fertilizing vegetables is very important, therefore, this study is concerned with investigating and evaluating the dry matter content (DM) and the accumulated heavy metal contents (HMs) in the root and leaf seedlings tissues of cucumber and summer squash plants as a result of using this fertilizer. Five ratios of mixtures (vermiculite: peat moss: TWC by weight) used in the experiment, and the TWC in the mixture represents 0, 5, 10, 15 and 20% (by wieght). The results indicated that, the DM contents in the root and leaf tissues were relatively close between cucumber and summer squash seedlings. However, they were higher in the root than in leaf tissues, particularly under 20% TWC. A TWC application ratio of 20% reduced concentrations of the most HMs in the two vegetable species seedlings due to high EC and pH levels. The amounts of HMs in vegetable species were not high, which proves the that transfer of HMs from the TWC substrate to the seedlings is determined chiefly by metal bioavailability and by a vegetable species. DM, mineral and nutritional quality of vegetable seedlings showed that substrates containing 5% and 10% TWC appeared to be the most suitable growing medium for economic vegetable seedlings; and it is recommended for use in the nursery production. Implications: The idea of this research revolves around the use of different proportions of tomato waste compost in fertilizing cucumber and summer squash seedlings and investigate the effect of this compost on dry matter (DM) and heavy metal (HMs) contents in the root and leaf tissues of the seedlings, and fruit quality of cucumber and summer squash plants.

Nano/micro-cellulose-based materials as remarkable sorbents for the remediation of agricultural resources from chemical pollutants

Overusing pesticides, fertilizers, and synthetic dyes has significantly increased their presence in various parts of the environment. The transportation of these pollutants into agricultural soil and water through rivers, soils, and groundwater has seriously threatened human and ecosystem health. Applying techniques and materials to clean up agricultural sources from pesticides, heavy metals (HMs), and synthetic dyes (SDs) is one of the major challenges in this century. The sorption technique offers a viable solution to remediate these chemical pollutants (CHPs). Cellulose-based materials have become popular in nano and micro scales because they are widely available, safe to use, biodegradable, and have a significant ability to absorb substances. Nanoscale cellulose-based materials exhibit greater capacity in absorbing pollutants compared to their microscale counterparts because they possess a larger surface area. Many available hydroxyl groups (-OH) and chemical and physical modifications enable the incorporation of CHPs on to cellulose-based materials. Following this potential, this review aims to comprehensively summarize recent advancements in the field of nano- and micro-cellulose-based materials as effective adsorbents for CHPs, given the abundance of cellulosic waste materials from agricultural residues. The recent developments pertaining to the enhancement of the sorption capacity of cellulose-based materials against pesticides, HMs, and SDs, are deliberated.

In Situ Synthesis of Zero-Valent Iron-Decorated Lignite Carbon for Aqueous Heavy Metal Remediation

Lignite’s large abundance, physicochemical properties and low cost are attractive for industrial wastewater remediation. However, directly applying lignite for wastewater treatment suffers low efficiency. Here, we synthesize highly efficient zero-valent iron (ZVI)-decorated lignite carbon through the in-situ carbonization of a lignite and FeCl2 mixture for heavy metal removal. The effect of carbonization temperature on the morphology, structure and crystallite phases of ZVI-decorated lignite carbons (ZVI-LXs) was investigated. At an optimized temperature (i.e., 1000 °C), ZVI particles were found evenly distributed on the lignite matrix with the particles between 20 to 190 nm. Moreover, ZVI particles were protected by a graphene shell that was formed in situ during the carbonization. The synthesized ZVI-L1000 exhibited higher Cu2+, Pb2+ and Cd2+ stripping capacities than pristine lignite in a wide pH range of 2.2–6.3 due to the surface-deposited ZVI particles. The maximum Langmuir adsorption capacities of ZVI-L1000 for Cd2+, Pb2+ and Cu2+ were 38.3, 55.2 and 42.5 mg/g at 25 °C, respectively, which were 7.8, 4.5 and 10.6 times greater than that of pristine lignite, respectively. ZVI-L1000 also exhibited a fast metal removal speed (~15 min), which is ideal for industrial wastewater treatment. The pseudo-second-order model fits well with all three adsorptions, indicating that chemical forces control their rate-limiting adsorption steps. The reduction mechanisms of ZVI-L1000 for heavy metals include reduction, precipitation and complexation.

Turmeric (Curcuma longa L.) tends to reduce the toxic effects of nickel (II) chloride in Allium cepa L. roots

The immense protection potential of plant-derived products against heavy metal toxicity has become a considerable field of research. The goal of the present study was to evaluate the mitigative ability of turmeric against nickel (II) chloride (NiCl₂)-related toxicity in the roots of Allium cepa L. For this purpose, one control (treated with tap water) and five treatment groups (treated with 440 mg/L turmeric, 880 mg/L turmeric, 1 mg/L NiCI₂, 1 mg/L NiCI₂ + 440 mg/L turmeric, and 1 mg/L NiCI₂ + 880 mg/L turmeric, respectively) of Allium bulbs were established. Experimental conditions were maintained at room temperature for 3 days. Physiological, biochemical, cytogenetic, and meristematic integrity parameters were analyzed in all groups. NiCl₂ reduced germination percentage, root elongation, and weight gain. Following NiCl₂ application, the frequency of aberrant chromosomes and micronuclei increased, while mitotic index decreased. NiCl₂ caused an increase in oxidative stress, which was evident by increased malondialdehyde level and catalytic activities of superoxide dismutase and catalase. Epidermal and cortex cell injuries as well as deformed cell nuclei and indistinct transmission tissue were observed as a result of NiCl₂ treatment. When applied alone, turmeric, which did not cause any negative effects, led to an improvement in all parameters depending on the dose when applied together with NiCl₂. Data from the study suggests that turmeric has remarkable protection potential against NiCl₂ in Allium cepa.

Advancements in heavy metals removal from effluents employing nano-adsorbents: Way towards cleaner production

Due to the development in science field which gives not only benefit but also introducesundesirable pollution to the environment. This pollution is due to poor discharge activities of industrial effluents into the soil and water bodies, surface run off from fields of agricultural lands, dumping of untreated wastes by municipalities, and mining activites, which deteriorates the cardinal virtue of our environment and causes menace to human health and life. Heavy metal(s), a natural constituent on earth's crust and economic important mineral, due to its recalcitrant effects creates heavy metal pollution which affects food chain and also reduces the quality of water. For this, many researchers have performed studies to find efficient methods for wastewater remediation. One of the most promising methods from economic point of view is adsorption, which is simple in design, but leads to use of a wide range of adsorbents and ease of operations. Due to advances in nanotechnology, many nanomaterials were used as adsorbents for wastewater remediation, because of their efficiency. Many researchers have reported that nanoadsorbents are unmitigatedly a fruitful solution to address this world's problem. This review presents a potent view on various classes of nanoadsorbents and their application to wastewater treatment. It provides a bird's eye view of the suitability of different types of nanomaterials for remediation of wastewater and Backspace gives up-to-date information about polymer based and silica-based nanoadsorbents.

Green synthesis of zero-valent iron nanoparticles and loading effect on activated carbon for furfural adsorption

The adsorption techniques are extensively used in dyes, metronidazole, aniline, wastewater treatment methods to remove certain pollutants. Furfural is organic in nature, considered a pollutant having a toxic effect on humans and their environment and especially aquatic species. Due to distinct characteristics of the adsorption technique, this technique can be utilized to adsorb furfural efficiently. As an environmentally friendly technique, the pomegranate peel was used to synthesized activated carbon and nanostructure of zerovalent iron impregnated on the synthesized activated carbon. The physicochemical and crystallinity characterization was done using Fourier transmission infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and Field emission scanning electron microscopy (FESEM). The nanoparticles are porous in structure having 821.74 m²/g specified surface area. The maximum amount of the adsorbent pores in the range of 3.08 nm shows the microporous structure and enhancement in adsorption capacity. The effects of increment in concentration of adsorbent, pH, reaction contact time and adsorbent dose, isothermal and kinetic behaviour were investigated. At the UV wavelength of 227 nm furfural adsorption was detected. The separation of the furfural from the aqueous solution was calculated at the 1 h reaction time at the composite dosage of 4 g/L, 250 mg/L adsorbent concentration and pH kept at 7. The 81.87% is the maximum removal attained by the nanocomposite in comparison to the activated carbon is 62.06%. Furfural adsorption was also analyzed by using the equations of isothermal and kinetics models. The adsorption process analysis depends on the Freundlich isotherm and Intra-particle diffusion than the other models. The maximum adsorbent of the composite was determined by the Langmuir model which is 222.22 mg/g. The furfural removal enhances as the adsorbent dose enhances. The developed zerovalent iron nanoparticles incorporated on activated carbon (AC/nZVI) from pomegranate peel extract are feasible as an efficient and inexpensive adsorbent to eliminate furfural from a liquid solution.

Heavy Metals and Pesticides Toxicity in Agricultural Soil and Plants: Ecological Risks and Human Health Implications

Environmental problems have always received immense attention from scientists. Toxicants pollution is a critical environmental concern that has posed serious threats to human health and agricultural production. Heavy metals and pesticides are top of the list of environmental toxicants endangering nature. This review focuses on the toxic effect of heavy metals (cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn)) and pesticides (insecticides, herbicides, and fungicides) adversely influencing the agricultural ecosystem (plant and soil) and human health. Furthermore, heavy metals accumulation and pesticide residues in soils and plants have been discussed in detail. In addition, the characteristics of contaminated soil and plant physiological parameters have been reviewed. Moreover, human diseases caused by exposure to heavy metals and pesticides were also reported. The bioaccumulation, mechanism of action, and transmission pathways of both heavy metals and pesticides are emphasized. In addition, the bioavailability in soil and plant uptake of these contaminants has also been considered. Meanwhile, the synergistic and antagonistic interactions between heavy metals and pesticides and their combined toxic effects have been discussed. Previous relevant studies are included to cover all aspects of this review. The information in this review provides deep insights into the understanding of environmental toxicants and their hazardous effects.