Acid-treated pomegranate peel; An efficient biosorbent for the excision of hexavalent chromium from wastewater

Pomegranate peel adsorbents for water pollutants removal: preparation, characterization and applications

Pomegranate peel waste in the forms of raw biomass, biochar and activated carbon has been explored as adsorbents in water treatment. This review examined and discussed published works between 2008 and 2024 that focused on the utilization of pomegranate peel waste adsorbents with emphasis on preparation strategies, characterization techniques and applications. The thermal and chemical activation have shown to improve the structural and chemical properties of the resultant adsorbent materials to effectively adsorb various pollutants such as dyes, heavy metals, organics, inorganic nonmetals, and pharmaceuticals from water. The performance was compared and the avenues for future research was highlighted to shed insight into the potential of pomegranate peel adsorbents for environmental protection.

Removal of Arsenic(V) from wastewater using calcined eggshells as a cost-effective adsorbent

This study investigates calcined eggshells (CES) as an effective adsorbent for the remediation of As(V). Characterization of CES was performed using zeta potential analysis, FTIR, XRD and SEM-EDX. Batch studies were conducted to examine the effects of pH, adsorption kinetics, and adsorption isotherms to assess efficacy. The adsorption of As(V) followed the Langmuir isotherm and pseudo-second-order kinetics, with a maximum capacity of 91.05 mg g⁻1 at pH 6.0 and 298 K. The presence of additional anions such as chloride, sulfate, or nitrate had no significant impact on the biosorption of arsenate. However, the introduction of phosphate ions notably decreased the rate of arsenic adsorption. CES was easily regenerated with an alkaline solution and showed excellent reusability over four cycles. Thermodynamic studies confirmed the spontaneity and feasibility of the biosorption process. This study highlights that CES is a promising adsorbent for As(V) removal from contaminated water.

A comprehensive study on pomegranate (Punicagranatum) peels as a low-cost biosorbent: adsorption mechanisms, application, regeneration, and cost analysis

This study investigates the potential of utilizing pomegranate peel, a waste material, as an environmentally friendly adsorbent for the removal of methylene blue (MB) from wastewater. The novelty of this study lies in producing a competitive adsorbent (96% removal in a reasonably short contact time), very low cost, from a biowaste material and in providing cost analysis, regeneration method, application, and a mechanism based on a set of results that are in harmony with each other. Characterization of the purified pomegranate (Punicagranatum) peels (PP) inferred remarkable acidic sites. The MB removal was observed to increase with increasing dosages of adsorbent, contact time (93-94% removal took place in the first 30-40 min), agitation speed (the amount of MB removed increased with increasing agitation speed up to 160 rpm), pH (increasing solution pH up to pH 8.0, the removal efficiency of MB by PP increased), and MB initial concentrations. The experimental results of MB adsorption on PP were best fitted to the Temkin isotherm model and the kinetic studies showed that the adsorption rate was best fitted to the pseudo-second-order (PSO) model showing a correlation coefficient R2 of 0.969-0.991. Thermodynamic investigations demonstrated that the removal of MB dye utilizing PP may be due to a spontaneous, electrostatic, chemical, and exothermic interaction with a heterogeneous adsorption mechanism. Adsorption is anticipated to begin with attraction between cationic MB and negatively charged active functional groups on adsorbent's surface, soon to be followed by multisite chemical interaction. The results (up to 96% removal) show that pomegranate peels could be used as a potential eco-friendly, cost-effective, and efficient biosorbent for dye removal from wastewaters. With an average removal effectiveness of 86.8%, PP were successfully utilized to remove MB from MB-spiked actual river water samples.

Loading of anionic surfactant on eco-friendly biochar and its applications in Cr(VI) removal: adsorption, kinetics, and reusability studies

Surfactant-modified biochar is a viable adsorbent for eliminating Cr(VI) from synthetic wastewater. The biochar obtained from the zea mays plant (BC) was tailored with sodium dodecyl sulfate (SDS) as an anionic surfactant forming SDS-BC adsorbent. Different controlling conditions have been evaluated including pH of the solution, biomass concentration, primary Cr(VI) concentration, time of adsorption, and temperature. Under the best controlling circumstances, the percentage of removal has attained 99%. The pseudo-second-order kinetic model best described the removal process, according to the kinetic data, while the Temkin model, one of the applicable adsorption isotherm models, well expressed the adsorption process. The thermodynamic parameters were computed, which disclosed the spontaneity and exothermic character of the Cr(VI) elimination. According to the regeneration cycles, SDS-BC was cost-effective and had a good removal capability.

Surfactant-modified zein nanoparticles adsorbents for ultrafast and efficient removal of Cr(VI)

The adsorption and removal of heavy metal ions Cr(VI) is of great significance for human health and ecological environment. Here, an ultrafast and high efficient adsorbent for Cr(VI) was developed based on cetyltrimethylammonium bromide (CTAB)-modified zein nanoparticles (C-ZNPs). In comparison to pristine zein nanoparticles (ZNPs) (11.199 m2 g-1), the surfactant-modified C-ZNPs exhibited larger specific surface area (17.002 m2 g-1). Moreover, C-ZNPs had superior dispersion and more positive charge distribution, which contributed to the improvement for adsorption performance. The results showed that the saturated adsorption of Cr(VI) was reached up to 192.27 mg/g using the C-ZNPs nanosorbent at T = 298 K, pH = 4, t = 10s, and C0 = 125 mg/L. The removal rate was significantly faster than that reported natural polymer-based adsorbents. The experimental values were followed Freundich isothermal model and pseudo-second-order kinetic model, indicating that the adsorption occurred primarily through a multimolecular layer adsorption process, with a strong emphasis on chemisorption. Mechanistic investigations further revealed that the adsorption of Cr(VI) onto C-ZNPs was mediated by various interactions, including electrostatic attraction, complexation, and ion exchange. These findings provide insights into the efficient removal of Cr(VI) by C-ZNPs and suggest potential applications in water treatment and environmental remediation.

Recent and sustainable advances in phytoremediation of heavy metals from wastewater using aquatic plant species: Green approach

A key component in a nation's economic progress is industrialization, however, hazardous heavy metals that are detrimental to living things are typically present in the wastewater produced from various industries. Therefore, before wastewater is released into the environment, it must be treated to reduce the concentrations of the various heavy metals to maximum acceptable levels. Even though several biological, physical, and chemical remediation techniques are found to be efficient for the removal of heavy metals from wastewater, these techniques are costly and create more toxic secondary pollutants. However, phytoremediation is inexpensive, environmentally friendly, and simple to be applied as a green technology for heavy metal detoxification in wastewater. The present study provides a thorough comprehensive review of the mechanisms of phytoremediation, with an emphasis on the possible utilization of plant species for the treatment of wastewater containing heavy metals. We have discussed the concept, its applications, advantages, challenges, and independent variables that determine how successful and efficient phytoremediation could be in the decontamination of heavy metals from wastewater. Additionally, we argue that the standards for choosing aquatic plant species for target heavy metal removal ought to be taken into account, as they influence various aspects of phytoremediation efficiency. Following the comprehensive and critical analysis of relevant literature, aquatic plant species are promising for sustainable remediation of heavy metals. However, several knowledge gaps identified from the review need to be taken into consideration and possibly addressed. Therefore, the review provides perspectives that indicate research needs and future directions on the application of plant species in heavy metal remediation.

Study on the adsorption of Zn(II) and Cu(II) in acid mine drainage by fly ash loaded nano-FeS

Aiming at the acid mine drainage (AMD) in zinc, copper and other heavy metals treatment difficulties, severe pollution of soil and water environment and other problems. Through the ultrasonic precipitation method, this study prepared fly ash-loaded nano-FeS composites (nFeS-F). The effects of nFeS-F dosage, pH, stirring rate, reaction time and initial concentration of the solution on the adsorption of Zn(II) and Cu(II) were investigated. The data were fitted by Lagergren first and second-order kinetic equations, Internal diffusion equation, Langmuir and Freundlich isotherm models, and combined with SEM, TEM, FTIR, TGA, and XPS assays to reveal the mechanism of nFeS-F adsorption of Zn(II) and Cu(II). The results demonstrated that: The removal of Zn(II) and Cu(II) by nFeS-F could reach 83.36% and 70.40%, respectively (The dosage was 8 g/L, pH was 4, time was 150 min, and concentration was 100 mg/L). The adsorption process, mainly chemical adsorption, conforms to the Lagergren second-order kinetic equation (R2 = 0.9952 and 0.9932). The adsorption isotherms have a higher fitting degree with the Langmuir model (R2 = 0.9964 and 0.9966), and the adsorption is a monolayer adsorption process. This study can provide a reference for treating heavy metals in acid mine drainage and resource utilization of fly ash.

A promising approach for the removal of hexavalent and trivalent chromium from aqueous solution using low-cost biomaterial

Heavy metal pollution is an enduring environmental challenge that calls for sustainable and eco-friendly solutions. One promising approach is to harness discarded plant biomass as a highly efficient environmental friendly adsorbents. In this context, a noteworthy study has spotlighted the employment of Euryale ferox Salisbury seed coat (E.feroxSC) for the exclusion of trivalent and hexavalent chromium ions. This study aims to transform discarded plant residue into a novel, environmentally friendly, and cost-effective alternative adsorbent, offering a compelling alternative to more expensive adsorption methods. By repurposing natural materials, we can contribute to mitigating heavy-metal pollution while promoting sustainable and economically viable solutions in environmental remediation. The effect of different parameters, i.e., chromium ions' initial concentration (5-25 mg L-1), solution pH (2-7), adsorbent dosage (0.2-2.4 g L-1), contact time (20-240 min), and temperature (298-313 K), were investigated. E.feroxSC proved highly effective, achieving 96.5% removal of Cr(III) ions at pH 6 and 97.7% removal of Cr(VI) ions at pH 2, with a maximum biosorption capacity of 18.33 mg/g for Cr(III) and 13.64 mg/g for Cr(VI), making it a promising, eco-friendly adsorbent for tackling heavy-metal pollution. The adsorption process followed the pseudo-second-order kinetic model, aligning well with the Langmuir isotherm, exhibited favorable thermodynamics, and was characterized as feasible, spontaneous, and endothermic with physisorption mechanisms. The investigation revealed that E.feroxSC effectively adsorbed Cr(VI) which could be rejuvenated in a basic solution with minimal depletion in its adsorption capacity. Conversely, E.feroxSC's adsorption of Cr(III) demanded rejuvenation in an acidic milieu, exhibiting comparatively less efficient restoration.

Parameter Influence, Characterization and Adsorption Mechanism Studies of Alkaline-Hydrolyzed Garcinia kola Hull Particles for Cr(VI) Sequestration

Despite the regulations by The World Health Organization (WHO) on the permissible limit of chromium, many industries still discharge wastewater polluted with chromium into the environment irrationally. This poses a lot of risk to aquatic lives and humans because of its carcinogenic and toxic attributes. Thus, treatment of industrial wastewater polluted with chromium is highly imperative before its disposal. Nonetheless, the hulls generated from Garcinia kola in our various farmlands also causes environmental pollution when dumped unknowingly. In this present study, Garcinia kola hull particles (GK-HP) was hydrolyzed using NaOH and applied as adsorbent for Cr(VI) sequestration. The raw Garcinia kola hull particles (rGK-HP) and modified Garcinia kola hull particles (cMGK-HP) were characterized using Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), powder X-ray diffractometry (XRD), Fourier-Transform-Infrared (FTIR), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS) and point of zero charge (pHpzc). The influence of pH, adsorbent dose, contact time, temperature and adsorbate initial concentration on Cr(VI) sequestration were examined. The cMGK-HP was able to remove 96.25% of Cr(VI) from solution and proved to be effective than rGK-HP. The amount of Cr(VI) removed from solution decreased as the pH and adsorbate initial concentration were increased. However, the amount increased as the adsorbent dose, contact time and temperature were increased. Change in morphological structure, textural property, spectral peak, phase composition and adsorbents chemical composition before and after Cr(VI) sequestration from solution were proved by SEM, BET, FTIR, XRD, and EDS analyses respectively. The isotherm and kinetic studies suggest Cr(VI) adsorption on adsorbents' surface to be monolayer in nature and adsorption data to be well-fitted into pseudo second order model respectively. The cMGK-HP possessed excellent reusability attribute and high thermal stability as shown by TGA. In conclusion, cMGK-HP could effectively be used as an adsorbent for Cr(VI) sequestration from solution.

Studies on ultrafast and remarkable removal of phosphate from sewage water by metal-organic frameworks

In the proposed research, a lanthanum-doped metal-organic framework (La-ATP) has been synthesised to remove phosphate from contaminated aqueous solutions. La-ATP was synthesised by a green energy-saving route using microwave irradiation and exhibited a phenomenal sorption capacity of 290 mg/g for the removal of phosphate. At a minimal dose of 0.1 g/L, 25 mg/L of phosphate gets reduced to 6.3 mg/L within 5 min and reaches equilibrium in 25 min. The isoelectric point of La-ATP was found to be 8.99, and it is efficient in removing phosphate over a wide range of pH 5-10. The existence of commonly occurring competing anions like sulphate, fluoride, chloride, arsenate, bicarbonate, and nitrate does not affect the uptake capacity of La-ATP towards phosphate ions. Furthermore, the robustness of La-ATP is demonstrated by its applicability to remove phosphate from real-life sewage water by reducing 10 mg/L of phosphorus from sewage water to < 0.02 mg/L. The primary mechanism governing phosphate removal was found to be ionic interaction and ligand exchange. Therefore, La-ATP can be considered a viable candidate for the treatment of eutrophic water streams because of its high sorption capacity, super-fast kinetics, and adaptability to contaminated sewage.

Efficient Cr(VI) sequestration from aqueous solution by chemically modified Garcinia kola hull particles: characterization, isotherm, kinetic, and thermodynamic studies

There is a need for the removal of hexavalent chromium from contaminated water prior to its discharge into the environment, as part of industrial effluents, due to its toxic nature. In this present study, an adsorbent prepared via chemical modification of Garcinia kola hull particles (GK-HP) using NaOH was applied for Cr(VI) sequestration from aqueous solution. Both the raw (rGK-HP) and chemically modified Garcinia kola hull particles (cMGK-HP) were characterized using BET, SEM, XRD, FTIR, TGA, and EDS. The effects of pH, contact time, adsorbent dose, adsorbate initial concentration, and temperature on Cr(VI) sequestration were examined. The adsorbent, cMGK-HP, proved to be more effective for the adsorption process than rGK-HP with 96.25% removal efficiency at a pH of 2, a contact time of 60 min, an adsorbent dose of 5 g/L, Cr(VI) initial concentration of 20 mg/L and a temperature of 40°C. Isotherm and kinetic studies showed experimental data to be well-fitted with Langmuir isotherm and follow the pseudo-second-order kinetic model. The thermodynamic study revealed adsorption nature to be feasible, occur via physisorption, spontaneous, and exothermic. Changes in morphological structure, textural property, spectral peak, phase composition, and chemical composition of adsorbents before and after Cr(VI) sequestration from solution were proved by SEM, BET, FTIR, XRD, and EDS analyses, respectively. cMGK-HP possessed excellent reusability attribute and high thermal stability as shown by TGA. In conclusion, the adsorption capacity of cMGK-HP is better than many other adsorbents generated from agrowastes used in previous studies for Cr(VI) removal.