Evaluating Cu(II) Removal From Aqueous Solutions with Response Surface Methodology by Using Novel Synthesized CaCO3 Nanoparticles Prepared in a Colloidal Gas Aphron System

Silica nanoparticles are novel aqueous additive mitigating heavy metals toxicity and improving the health of African catfish, Clarias gariepinus

Silica nanoparticles (SiNPs) are among the non-toxic nanoparticles (NPs) that have magnetic capabilities. It is hypothesized that SiNPs may be able to reduce toxic effects exerted by a mixture of lead (Pb) and mercury (Hg) in African catfish Clarias gariepinus. The in vitro magnetic potential of SiNPs to absorb Pb and Hg was tested. Fish (N = 240) were divided into four groups in triplicates for 30 days. The first group served as control and the second group (SiNPs) was exposed to 1/10 of 96 h LC50 of SiNPs (14.45 mg/L). The third group (HMM) was exposed to 1/10 of 96-h LC50 of a mixture of mercury chloride (HgCl₂) and lead chloride (PbCl₂) equal to 0.04 mg/ L and 23.1 mg/L. The fourth group (SiNPs+ HMM) was exposed to a suspension composed of SiNPs, HgCl₂, and PbCl₂ at the same concentrations as the third group. Results showed that fish exposed to heavy metals revealed the following consequences; a significant decrease in hematological, immunological (complement-3 and nitric oxide), and antioxidants (total antioxidant capacity, glutathione peroxidase, superoxide dismutase, and catalase) indices, down-regulation of IL-1β, IL-8, TGF-β, NF-κβ, HSP70, and Hepcidin genes, the highest mortality rate (48.33%), higher values of alkaline phosphatase, alanine, and aspartate aminotransferases, urea, creatinine, and branchial malondialdehyde, marked up-regulation of CC chemokine and CXC chemokines, and high HMs residues levels in muscles. Extensive pathology showed degeneration with diffuse vacuolation of hepatopancreatic cells and hemorrhage in the HMM group. Interestingly, the exposed group to SiNPs and HMM demonstrated a decline of HMs concentration in fish muscles and modulated the abovementioned parameters with the regeneration of histological alterations of liver and gills. Based on the study outcomes, we highlight the importance and the safety of SiNPs as a novel aqueous additive to alleviate HMs toxicity and recommend using SiNPs for enhancing fish performance for sustaining aquaculture without adverting safety of human health by their little accumulation in muscular tissue.

Size-tunable effect of CaCO3/nanocellulose hybrid composites on the removal of paracetamol from aqueous solution

Paracetamol is a ubiquitous drug used by animals and humans but is not fully metabolized within their bodies, and thus often finds its way into raw wastewater. This study represents a new class of adsorbent nanocomposite with high adsorption capacity towards paracetamol removal. Herein, both the kinetic study and the removal of paracetamol from aqueous solutions were investigated in terms of diverse CaCO₃/nanocellulose composites with different surface charges and different particle sizes. To fine-tune these parameters, the latter was hydrothermally synthesized by manipulating of three nanocelluloses types. Precisely, micro-crystalline cellulose (MCC), nano-crystalline cellulose (CNC), and nano-fibrillated cellulose (NFC) were used as templates for precipitating CaCO₃ particles from CaCl₂ solution with the aid of Na₂CO₃. Results revealed the successful in situ deposition of calcite form of CaCO₃ with size varied relying on the base of nanocellulose. For MCC, CNC, and NFC, the size of CaCO₃ was disclosed in the range of 850-1200 nm, 350-600 nm, and 150-200 nm, respectively, regarding their surface charge. While the process of paracetamol adsorption was described by Freundlich and Langmuir isotherms, it was observed that, for MCC, the best fit of the experimental data was achieved with the Freundlich model, while the Langmuir model was the most appropriate for CNC and NFC. Also, the highest max adsorption capacities of paracetamol varied respectively to both size and surface charge of hybrid composite used. Among them, MCC/CaCO₃ composite exhibited the highest max adsorption capacity at 428 mg g^-1, clarifying that the low surface zeta potential of the latter hybrid nanocomposite is responsible for the accumulation of CaCO₃ at a bigger size with a higher affinity to adsorb paracetamol with the highest capacity due to its weak repulsion. Results also demonstrated that the material is highly effective and economical for removal of paracetamol and reusability with marginal diminishing in adsorption capacity up to 10% after five reuse cycles.

Removal of copper from sulfate solutions using biochar derived from crab processing by-product

Increasing metal demand is accelerating the mining and processing of minerals, however to ensure sustainable growth innovative approaches are required to better manage associated effluents. Biochar from the fast pyrolysis of residues from fishery and forestry operations has been studied as a low-cost, environmentally and economically friendly method for treating mine tailings and processing effluents. However, the bulk of the studies focus on terrestrial biomass (e.g. wood) and do not include potential inhibition/enhancement of adsorption due to pH controlling compounds. In this work biochar generated from snow crab (Chionoecetes Opilio) processing was studied as an adsorbent for copper solutions containing sulfate (a key compound in sulfide ore mining waters) with the objective of assessing adsorption capacity and the impact of sulfate on copper adsorption. The biochar, a porous structure comprised of calcite (CaCO₃), was alkaline and has a negative zeta potential under neutral and basic conditions. The crab biochar removed over 99% of Cu²⁺ from a 100 mg/L solution (sourced as CuSO₄) at a dosage of 5 g/L, which was higher than lignocellulosic biochar at the same biochar dosage. While metal adsorption can often be impacted at acidic conditions, Cu²⁺ adsorption was not impacted by initial acidic pH due to the biochar's buffering capacity. The Pseudo-Second Order (PSO) model fit the adsorption rate with maximum adsorption achieved in approximately 2 h. The maximum adsorption isotherm capacity was 184.8 ± 10.2 mg/g for Cu²⁺, much higher than existing commercial activated carbons and previously studied lignocellulosic biochars and followed the Freundlich isotherm. The adsorption mechanism responsible for removal of Cu²⁺ was found to be precipitation, in the form of the mineral posnjakite (Cu₄[(OH)₆SO₄]·H₂O). These results indicate for the first time that crab-based biochars are capable of adsorbing large quantities of Cu²⁺ from sulfate-rich solution, while also buffering solution pH, demonstrating promise as an acid mine drainage treatment for removal of harmful metals and reduction of acidity.

Adsorption of lead ions from wastewater using nano silica spheres synthesized on calcium carbonate templates

Lead is a heavy metal that is bio accumulative and non-biodegradable that poses a threat to our health when it exists in excess in our bloodstream. It has found its way into wastewater from mostly chemical industrial processes. In this article, we investigated the adsorption and hence removal of lead (II) ions from wastewater in order to purify it for re-use in industrial processes or for plant and animal use. We synthesized nano silica hollow spheres (NSHS) and used them as adsorbents to remove lead ions from wastewater. When we characterized the NSHS using X-Ray diffraction, the amorphous nature of silica was evident with average crystal size of 39.5 nm. Scanning electron microscopy was used to determine the morphology of the adsorbent and the particles were found to be spherical in shape within a size range of 100–200 nm. Thermogravimetric analysis was used to determine the mass loss of NSHS which was ~2% at 800 °C. Our experimental results from adsorption studies showed that there was a linear relationship between temperature (27–60 °C) and adsorption efficiency and an inverse relationship between initial metal concentration (50–300 mg/L) and adsorption efficiency. At a maximum temperature of 60 °C and maximum initial metal concentration of 300 mg/L, the adsorption capacity was 200 mg/g and 262 mg/g, respectively while the adsorption efficiency was 99.6% and 87.4%, respectively. Our equilibrium and thermodynamic results revealed that the process was better modelled by the Langmuir adsorption isotherm (q_max = 266.89 mg/g and b = 0.89 L/mg). The adsorption process was both endothermic (ΔH = 97 kJ/mol) and spontaneous (ΔG = -22 kJ/mol). We can conclude that we were able to successfully synthesize NSHS, use them to remove lead (II) ions and the produced NSHS have a capacity that is higher than most other adsorbents investigated by other researchers.