Analytical Methods in Environmental Chemistry Journal

Abstract This study focused on the adsorption behavior of the cationic Crystal
Violet (CV) dye from aqueous solutions using a Co⁺²‒hectorite
composite as an adsorbent surface. The initial and equilibrium CV dye
concentrations were determined using a UV-Vis spectrophotometer. The
results were discussed and presented for the impacts of pH, primary CV
dye concentration, composite dosage, and temperature. The optimum
conditions were found for eliminating Crys tal Violet dye from the
aqueous solution at a pH 4, ideal temperature 293 K, and 0.5 g L^-1
of composite dose. The pseudo-second-order kinetic, intraparticle
diffusion analyzed the tes ts’ data and film diffusion models. Each
model’s defining features have been identified, and these models were
in good agreement and in charge of regulating the adsorption reaction.
The adsorption operation was also thermodynamically examined to
determine thermodynamic variables such as Gibbs free energy (ΔGo),
entropy (ΔS^o), activation energy ₍E_a), and enthalpy (ΔH^o). The negative
value of Gibbs free energy (ΔG^o) and enthalpy (ΔH^o) indicated that
the adsorption process was a spontaneous and exothermic reaction.
While the activation energy (E_a) data which fell within the normal
range for physisorption, was showed at  22.434 kJ mol^-1. 
The physical adsorption occurs between  CV dye and
 adsorbent .

Abstract In recent years, numerous researchers have concentrated on the process of turning waste into usable materials. Polystyrene and its modifications have received great attention over the past few decades due to their outstanding ion exchange behavior toward various toxic heavy metals in aqueous solutions. Therefore, this study is concerned with the preparation of three different cationic polymeric resins for the removal of Pb²⁺, Cd²⁺, and Fe³⁺ heavy metal ions from their contaminated water samples based on the sulfonated single-used polystyrene teacup waste (SPS), which was used to prepare sulfonated polystyrene-g-acrylamide monomer (SPS-g-Acryl) and sulfonated polystyrene-g-chitosan (SPS-g-Chit) using commercial chitosan (DD=85%) originally extracted from shrimp cortex. The concentrations of the selected heavy metal ions were measured before and after each experiment with a flame atomic absorption spectrometer (F-AAS). The analytical studies started by exploring the influence of pH (2, 4, 6, and 8) on removing the heavy metal ions Pb²⁺, Cd²+, and Fe³⁺ from their aqueous solutions. The obtained results revealed that as the pH of the analyzed ion solution is increased, the removal efficiency for ions increases. All three resins (SPS, SPS-g-Acryl, and SPS-g-Chit) had different removal efficiencies for the investigated ions, with SPS-g-Chit resin.

Abstract Arsenic is a highly toxic metalloid that forms different chemical states in nature, including arsenate and arsenite, as common inorganic forms. Exposure to arsenic may cause adverse effects on human health and the environment. Therefore, the detection of arsenic is critical. Exploring new approaches with low detection ranges and high sensitivity is crucial. This review paper consists of optical methods, including colorimetric and fluorometric methods, which detect arsenite and arsenate. Initially proposed colorimetric approaches such as the Gutzeit and molybdenum blue method can easily to use. However, the production of toxic substances limits their applications. Later, structurally modified molecules, nanoparticle-based assays, and their modifications are used for arsenic detection. Fluorometric methods also have noticeable attention to arsenic detection. Fluorescent approaches reported in this paper are based on semiconductor nanomaterials, other nanomaterials, and their modifications, etc. In addition, arsenate's catalytic and inhibitory activity on enzyme activity can be used to detect arsenic through colorimetric and fluorometric methods. This review highlighted the advantages, disadvantages, comparisons, and uses of colorimetric and fluorometric methods in detecting arsenite and arsenate.

Abstract The behavior of phenol was studied and determined using the modified carbon paste electrode (MCPE) with nickel oxide nanoparticles doped by nitrogen carbon quantum dots as nanoadsorbent (NiO - NCQD) and cyclic voltammetry (CV). The MCP electrode was manufactured in a laboratory. The modified carbon paste consisted of 12% (NiO-NCQD), ­ 44% of graphite powder and 44% of paraffin oil to get a modified carbonate paste. Cyclic voltammetry can provide behavior information; as such: diffusion coefficient (D), charge transfer coefficient (α.n_α), the mass transport (m_trans)  found that diffusion coefficient, the reduction of mass transport (m_trans) by increasing the phenol concentration in the solution, and increasing of constant K⁰ when the concentration of phenol increased in the solution.  Also, the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and Gibbs free energy (ΔG) are studied and calculated. In this study, E_HOMO=4.92eV, E_LUMO=0.32eV, and ΔG=-4.17 were considered. The drinking water samples from Latakia city were analyzed based on NiO-NCQD adsorbent using the MCPE method (NiO-NCQD/MCPE). The phenol concentration in the drinking water sample in Latakia was achieved less than the quantitative detection limit (LOQ), and the proposed procedure was validated by spiking samples.

Abstract In the last few years, using chemical insecticides to control the malaria vector has caused environmental pollution and resistance to chemical insecticides. This study aimed to investigate the chemical analysis of essential oils of Thymus carmanicus Jalas by gas chromatography and mass spectrometry (GC-MS) and toxicity activity against the major Iranian malaria vector, Anopheles stephensi. The essential oil of Thymus carmanicus Jalas was prepared from dried leaves using the hydro-distillation method. Gaschromatography-mass spectrometer (GC-MS) was used to analyze and identify thyme essential oil compounds. Bioassay was performed using World Health Organization (WHO) standard test. The T. Carmanicus Jalas essential oil consisted of 15 compounds, with Carvacrol (61%), Thymol (6%), and β-caryophyllene (5%) being the major components by volume. The LC₅₀ and LC₉₀ of thyme oil were 20.37 and 41.38 ppm at 24h after application, respectively. At 24h after application, significant differences were observed between the toxicity of 5%, 20%, 25%, 40%, 50%, and 80% concentrations of Thyme essential oil (P<0.05). The 80% concentration of Thyme essential oil exhibited 100% toxicity against A.stephensi larvae at 24h after application. T. Carmanicus has a rich source of bioactive compounds for use as a mosquito larvicide.

Abstract The continuous exposure of the environment to carcinogenic wastes and toxic chlorophenols such as pentachlorophenol (PCP) and 2,4,6-trichlorophenol (TCP) resulting from industrial production activities is become a great concern. The search for cost efficient and ecofriendly approach to phytoremediation of water will guarantee sustainability. The present research work is concerned with cost benefit evaluation, and the optimization modeling of the competitive biosorption of PCP and TCP from aqueous solution to Cana indica. L (CiL-plant) using response surface methodology (RSM) and artificial neural network (ANN) model. The predictive performances of the ANN model and the RSM were compared based on their statistical metrics. The antagonistic and synergetic effect of significant biosorption variables (pH, initial concentration, and exposure time) on the biosorption process were studied at p-values ≤0.005. The optimized output transcends to PCP and TCP removal rates of 90% and 87.99% efficiencies at predicted r-squared ≤0.9999, at 95% confidence interval. The cost benefit evaluation established that at the optimum conditions, the cost of operating the removal of TCP from aqueous solution will save $ 7.72 compared to PCP. The reliability of the optimization model based on design of experiment was proven to be more sustainable compared to the one-factor-at-a-time methodologies.

Abstract The present study aimed to extract pesticide residues in the field and greenhouse-grown tomatoes and homemade paste based on the  (QuEChERS) method before being determined by liquid chromatography-mass spectrometry (LC-MS). The mean difference in percentage reduction of deltamethrin (DLM) and acetamiprid (ACT) in raw tomatoes of greenhouse-grown was obtained at 91.42 and 90.00%, respectively, which was insignificantly more than filed condition (84.91% and 86.34%). Maximum reduction percentages of the DLM in paste under greenhouse and field tomato conditions were achieved by more than 95.86% and 93.11%, respectively. The residual concentration of both DLM (91.42%) and ACT (90.00%) in the greenhouse decreased more than the field (84.91% and 86.34%), respectively. Abamectin(ABA) reached below the MRL in a shorter time after spraying (2 days). Considering the pre-harvest interval (PHI) period of deltamethrin and abamectin can reach their residual concentration to the MRL in both conditions, which were determined by LC-MS. According to the results of the current study, 7 and 5 days can be suggested as the PHI period of the acetamiprid for field and greenhouse-grown tomatoes, respectively. Therefore, using pesticides in the proper dosage, considering appropriate PHI, and harvesting can reduce their residues in agricultural products.