Due to urbanization and industrialization, there has been an increase in solid waste generation and has become a global concern and leakage of leachate from landfills contaminate the soil and groundwater and hence can have a severe impact on human health. The present study aimed to determine the composition of toxic metals (Cr, Mn, Cu, As) and heavy metals (Cd, Ba, Hg, Pb) in soil and water by an inductively coupled plasma optical emission spectrometer (ICP-OES). To ensure accuracy during the analysis of Cr, Mn, Cu, As, Cd, Ba, Hg, and Pb in real samples, certified reference material (CRM, SRM 2709a) of San Joaquin soil and water (SRM 1640a) were analyzed and results were presented in terms of % recovery studies. The mean concentration of all the metals in soil and water did not exceed the limit set by the European Community (EU), WHO, and US EPA except Cu where the permissible limit defined by the EU is 50–140 mg/kg in soil. The soil is uncontaminated to moderately contaminated with respect to all metals except the Cu and Pb. Among the average daily dose (ADD) of soil, ADDing and ADDinh for children had the maximum dose for all metals than adults while ADDderm was higher in adults. Hazard quotient (HQ) trend in both adults and children was found in order HQing > HQderm > HQinh of soil for all metals except Ba which followed HQing > HQinh > HQderm. Hazard index (HI) values of soil for Cr and Pb in children were 7 and 7.5 times higher than adults respectively. Lifetime cancer risk (LCR) value for Cr by different exposure pathways of soil was 5.361 × 10−4 for children which are at the lower borderline of risk for cancer.
Microemulsions (μEs) are unique systems that offer exciting perspectives in biophysical research for mimicing biomembranes at the molecular level. In the present study, biocompatible μE formulation of a new oil-in-water (o/w) system comprising clove oil/Tween 20/2-propanol/water was accomplished for encapsulating an antibiotic, levofloxacin (LVF). The pseudoternary phase diagram was delineated at a constant cosurfactant/surfactant (2:1) ratio to meet the economic feasibility. The gradual changes occurring in the microstructure of the as-formulated four-component μEs were explored via multiple complementary characterization techniques. The results of electrical conductivity (σ), viscosity (η), and optical microscopic measurements suggested the existence of a percolation transition to a bicontinuous structure in the microregions of the as-formulated μE. LVF displayed a high solubility (5.0 wt %) at the pH of 6.9 in an optimum μE formulation comprising 2-propanol (36.4%), Tween 20 (18.2%), clove oil (20.7%), and water (24.7%). The LVF-loaded μE composition showed long-term stability for over 6 months of storage. Fourier transform IR analysis showed that LVF was stable inside the μE formulation, indicating the absence of any possible aggregation of LVF. Dynamic light scattering revealed that the average particle size of drug-free μE (64.5 ± 3.4 nm) increases to 129.7 ± 5.8 nm upon loading of LVF, suggesting the accumulation of LVF in the interfacial layers of the micelles. Moreover, fluorescence measurements indicated that LVF might be localized in the interfacial film of μE system, which may result in a controlled release of drug.
In the present investigation, brown
clay (BC) was modified with
didodecyldimethylammonium bromide (DDAB) to produce a sorbent (DDAB-BC),
which was characterized and applied for sorption of methylene blue
(MB) from aqueous media. BC was functionalized using DDAB by cation
exchange of the DDAB moiety with positive ions existing inside the
interlayer spaces of the BC. X-ray diffraction (XRD) studies confirmed
that the
d
-spacing of DDAB-BC became wider (3.39
Å) than that of BC (3.33 Å). Fourier transform infrared
spectroscopy (FTIR) and scanning electron microscopy (SEM) were exploited
to explore the functional groups and morphological structure of sorbents,
respectively. The Brunauer–Emmett–Teller (BET) surface
area, pore volume, and pore diameter of DDAB-BC were determined as
124.6841 m
2
/g, 0.316780 cm
3
/g, and 8.75102 nm,
respectively. Batch sorption investigations were carried out to determine
the optimum experimental conditions, using the one-factor one-time
procedure. The sorption of MB on DDAB-BC strongly obeyed the Langmuir
isotherm and agreed well with pseudo-second-order kinetics. Sorption
of MB onto DDAB-BC showed maximum efficiency (∼98%) and maximum
sorption capacity (∼164 mg/g) at optimal values of pertinent
factors: dye concentration (100 mg/L), pH (7), and temperature (55
°C). Sorption isothermal studies predicted that removal of MB
on DDAB-BC follows multilayer sorption at higher MB dye concentrations
and monolayer sorption at lower MB dye concentrations.
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