Dynamic adsorption studies for the removal of Cd (II) and Ni (II) from aqueous solutions using mahogany leaves

A dynamic adsorption study was carried out using mahogany leaves (ML) powder as an adsorbent for the removal of Cd (II) and Ni (II) from their aqueous solutions. The effects of contact time, adsorbent dose (5, 10 and 15 g), initial concentration (10, 15 and 20 mg/L), particle size (212, 150 and 106 μm) and pH of zero charge (pHpzc) on the adsorption of Cd (II) and Ni (II) ions onto mahogany leaves powder at pH of 4.5 were investigated. The results showed that, an increase in contact time and adsorbent dose increase the percentage removal of metals. The adsorption was found to be more effective at higher concentrations of metals and with smaller adsorbent particle size. The physicochemical characteristics of the adsorbent such as attrition loss, moisture content, bulk density, pore (void) volume, iodine number/surface area, SEM and FTIR of the stationary phase were investigated. Modelling of dynamics of the fixed-bed adsorption process was studied, and the application of different models to describe the breakthrough curves showed that, Yoon–Nelson is the best fit model with values of correlation coefficient R2 of 0.9048 and 0.8557 for cadmium and nickel respectively gave better results for the operating conditions. Recommendation was made such that, mahogany leaves should be studied for the remediation of other heavy metals, such as lead, chromium, mercury, zinc and uranium among others.Keywords: adsorption, cadmium, mahogany, nicke

Adsorption of Alkali Blue, Metanil Yellow and Neutral Red dyes Using Copper (II) Oxide particles: Kinetic and Thermodynamic Studies

Copper (II) oxide particles (CuO-Ps) was synthesized and used for the removal of Metanil Yellow (MY), Alkali Blue (AB) and Neutral Red (NR). The influence of variables such as contact time, dosage, temperature and agitation speed for the adsorption process were investigated using Batch Adsorption Method. The synthesized particles were characterized using UV-Visible spectroscopy with a broad peak of 273 nm indicating the changein colour of the CuO-Ps from blue to brownish black with the formation of CuO-Ps. FTIR were carried out to determine the functional groups present at the surface of the particle with functional groups such as –OH, C=C, C-H, C≡C detected. SEM analysis of the CuO-Ps was carried out. The changes in the morphology was observed which is due to the attachment of the dye molecules at the surface of the particles. The percentage removal and optimum contact time of MY, AB and NR were obtained as 70.7% at 25 min, 84.8% at 10 mins and56.9% at 30 min respectively. Kinetics studies of all the dyes shows that adsorption process fits pseudo second order with the experimental values of qe 2.844, 4.242 and3.536 for NR, AB and MY respectively being closer to the calculated values of the qe 2.739, 4.108 and3.222 for NR, AB and MY respectively. Non linearity from Bangham’s plot shows that both film and pore diffusion played an important role in all the three adsorption processes. Negative values of ΔH andΔG revealed that the process was exothermic and feasible. Positive and Negative values for ΔS showed spontaneity of the process and decrease in randomness. Values of ΔH -6.70, -20.30 and-7.76 kJ/mol for AB, NR and MY, respectively confirmed the adsorption process as physical in nature. The results indicated that copper (II) oxide particles can be used as a low cost adsorbent for the removal of MY, AB and NR from aqueous solutions.Keywords: Adsorption, CuO, FTIR, Kinetic, SEM, Thermodynamics, UV-Visible spectroscop

Reclamation of malachite green-bearing wastewater using desert date seed shell: adsorption isotherms, desorption and reusability studies

A low-cost activated carbon adsorbent was prepared from desert date seed shell (DDSS) and utilized for the removal of hazardous malachite green (MG) from aqueous solution using batch mode technique. Different isotherm models were applied to acquire the theoretical data of MG adsorption onto the adsobent at variable initial concentration of 100-1000 mg dm-3. Based on the coefficient of determination (R2), isotherm models exhibit the following sequence: Freundlich > Langmuir > Redlich-Peterson > Temkin > Jovanovic > Harkin- Jura > Elovich > Dubinin-Radushkevic. The maximum monolayer capacity of the adsorbent was found to be 312.5 mg g-1 at 303 K. The mean free energy value (0.91 kJ mol-1) obtained from D-R isotherm suggests that the adsorption process follows physisorption mechanism. Desorption studies for reusability revealed that acetic acid offered the best recovery (52.09%) and the process follow pseudo-second-order kinetics. The conducted reusability test revealed the decline of the adsorbent performance from 96.5% MG removal down to 70.5% MG removal after 5 successive adsorption/desorption cycles.Keywords: Activated Carbon, Desorption, Isotherms, Malachite Green, Reusabilit

Mangifera indica leaves powder for the removal of rhodamine B.: isotherm and kinetic studies

Adsorption of Rhodamine B (RB) dye onto a non-conventional plant biosorbent, Mangifera indica (mango tree) leaves powder (MLP), was investigated in batch adsorption experiments. Process parameters which include initial dye concentration, contact time and adsorbent dosage were varied in order to evaluate their influence on the adsorption process. Maximum adsorption efficiency (87.00%) was obtained at 75 min. The experimental data fitted well to pseudo-second-order kinetic model and the intra-particle diffusion model, however, diffusion was not only the rate-controlling step. The isotherm modeling suggested that Freundlich isotherm best described the process, with R2 value of 0.972, which is an indication of presence of multi-layer adsorption. The nf value (1.073) shows the adsorption process is favourable, indicating a physisorption. FT-IR results showed the shifting of peak down field and up field which depicts an interaction between the adsorbent and the dye molecules. The results showed that Mangifera indica leaves powder can be used as a low-cost adsorbent for the removal of RB from aqueous media.Keywords: Adsorption, Isotherms, Kinetics, Mangifera indica, Rhodamine B

Green synthesis of zinc nanoparticles using Ipomoea asarifolia leaves extract and its adsorption properties for the removal of dyes

In this paper, a green method is reported for the synthesis and characterization of zinc nanoparticles using Ipomoea asarifolia leaf extract as reducing and capping agent together with polyethylene glycol (PEG-10000) as stabilizing agent. The biosynthesized zinc nanoparticles were characterized by UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM); and were used as adsorbent for the removal of Bromophenol blue (BPB), and Eriochrome black T (EBT) dyes. Isotherms, kinetics and thermodynamics of the adsorption process were studied with the view to understand the adsorption mechanism. The adsorption isotherms were closely described by Freundlich isotherm model with correlation coefficient (R2) of 0.99. The adsorption kinetics data were well fitted by the pseudo-second-order rate model with high regression coefficient (0.998). The intra particle diffusion of BPB anId EBT on ZnNPs represents the rate-limiting step. The adsorption capacity increases with the increase in temperature (from 298 to 318K) and thermodynamic calculations suggested that the adsorption of the dyes onto ZnNPs is an endothermic process with ΔH values of 10.78kJ/mol for BPB and 14.14 kJ/mol for EBT respectively.Keywords: Adsorption, Bromophenol blue, Eriochrome black T, Ipomoea asarifolia, Zinc nanoparticle

Adsorption thermodynamics of some basic dyes uptake from aqueous solution using Albizia lebbeck shells

The efficiency of Albizia lebbeck shell for the adsorption of auramine yellow (AY), basic malachite green (BMG) and basic violet (BV) dyes from aqueous solution has been studied in a batch system. The effects of contact time, adsorbent dosage, initial dye concentration, solution pH and temperature have been investigated and the optimum conditions were determined. Thermodynamic parameters such as enthalpy change (ΔHo), entropy change (ΔSo) and free energy change (ΔGo) were studied and the values were -53,475.648 Jmol-1, -138.345 Jmol-1K-1 and -11,557.125 Jmol-1 respectively for the adsorption of auramine yellow and -12,6730.302 Jmol-1, -389.012 Jmol-1K-1 and -8,859.648 Jmol-1 respectively for the adsorption of basic malachite green indicating exothermic, non-spontaneous and feasible processes for AY and BMG at tested low and high temperatures of 303k and 323k. However, the enthalpy, entropy and free energy changes’ values for the adsorption of basic violet were 19,030.746 Jmol-1, 83.639 Jmol-1K-1 and 18,335.371 Jmol-1 respectively indicating endothermic, spontaneous and infeasible process at 303k but feasible at 323k. Surface characterization of the adsorbent based on scanning electron microscopy (SEM) were studied before and after adsorption, and the results indicate that the adsorbent could be effective due to its large number of external cavities on the surface. Therefore, Albizia lebbeck shells could serve as an effective adsorbent for the removal of organic colorants from textile wastewater prior to disposal since it has 94.2, 72.4 and 85.3% adsorption efficiency values for the removal of AY, BMG and BV respectively.Keywords: Adsorption, Albizia lebbeck Shells, Basic Dyes, Thermodynamic

Removal of crystal violet from aqueous solution using desert date (Balanites aegyptiaca) seed shell

The feasibility of utilizing desert date seed shell (DDSS) as an alternative low-cost adsorbent for the removal of hazardous crystal violet (CV) dye from aqueous solution was investigated. The prepared adsorbent was characterized by Fourier transform infrared (FTIR) spectroscopy (Cary 630; Agilent Technologies) and scanning electron microscopy (PRO: X: Phenonm World 800-07334). The influence of operational parameters such as contact time, adsorbent dosage, pH, and temperature were studied using batch mode technique. The obtained results showed that 60 min contact time, 0.4g adsorbent dose, solution pH of 8 and 60 oC temperature resulted in maximum CV removal. The equilibrium data fitted very well to Freundlich model (R 2 = 0.9983) and the KF and 1/n values were found to be 31.21 dm3g -1 and 0.828 respectively. The maximum adsorption capacity of DDSS for CV as determined by Langmuir isotherm is 294.12 mg g -1at 303K. Kinetic analysis revealed that the pseudo second order was the best model (R 2 = 0.9999) for the description of CV uptake with the experimental value of qe 20.3575 mg g -1 being closer to the calculated value of the qe 20.3651 mg g -1 . Thermodynamic studies revealed a negative value for ∆G o (-11.07 kJ mol -1 ) and a positive value for ∆H o (33.75 kJ mol -1 ) and ∆S o (134.9 J mol -1 K-1  ). These indicated the  spontaneous and endothermic nature of the adsorption process. Keywords: Adsorption, Desert date seed shell, Crystal violet, Batch  mode, Modelin

Thermodynamic Study on the Adsorptive Removal of Cr(Vi) and Ni(Ii) Metal Ions Using Schiff Base as Adsorbent.

In this work, the efficiency of a Schiff base derived from ethylenediamine and benzaldehyde in the removal of Cr(VI) and Ni(II) ions from their aqueous solution in batch mode was investigated. The FT-IR spectra of the Schiff base before and after adsorption showed bands at 1640 cm-1 and 1644 cm-1which indicate the formation of C=N functional group and coordination of the metal ions respectively. The Schiff base was found to be insoluble in water. SEM results of the Schiff base before and after adsorption revealed different morphology. Adsorption parameters were studied at equilibrium time of 80 min and 60 min for Cr(VI) and Ni(II) respectively. The optimum pH value for the adsorption of Cr(VI) and Ni(II) was 4 and 8 respectively. The thermodynamic parameters such as change in Gibbs free energy ((G), enthalpy ((H) and entropy ((S) were calculated at different temperatures. The values of Gibbs free energy were found to be negative, which that the adsorption process was spontaneous and feasible. The heat for adsorption of Cr(VI) and Ni(II) ions were 80928 J/mol and 47248 J/mol respectively, and this indicates the removal of Cr(VI) and Ni(II) is through chemisorption and endothermic. Furthermore, entropy values 277 J/molK-1 for Cr and 168 J/molK-1 revealed the spontaneity of the process

Critical motivational factors for enhancing employee performance in construction firms based on correlation and principal component analyses

Over the years, construction firms have often hinged their success on the effective motivation of their employees so as to ensure productivity and improved performance. Previous studies noted that various factors affect the motivational level of employees with regards to work performance. However, due to the difference in employee needs, not all motivational factors have influence on employees’ performance. This study sets out to assess the influence of motivational factors on the performance of employees in construction firms. The study aim was achieved through the identification and assessment of critical motivational factors (intrinsic and extrinsic) in the Nigerian construction firms. Perceptual data was collected from employees of selected construction firms using a structured questionnaire. Data collected was analyzed using descriptive and inferential statistics. Motivational factors were ranked based on respective mean scores from the most to the least influential. Extrinsic motivational factors such as promotion when due, availability of resources and provision of transportation for employees were found to be the most influential factors on performance. Whereas, constant supervision was found to have the least influence on performance. Findings of the study provides construction firms with empirical data on factors that influence the motivation level of employees with a view to optimizing employee productivity. It is recommended that construction firms should pay close attention to the peculiar needs of respective employees which aids in optimizing organizational performance. Keywords: Motivation, Employee performance, construction firms, critical factor

Analysis of heavy metals concentration in Kano herbal preparations for major disease conditions

The use of herbal medicines for treatment, management and prevention of different disease conditions has been as old as human history. These herbs usually contained some chemical substances which are considered as beneficial, while others were not. Study of the levels of some essential (Copper, Cadmium, Cobalt, Iron, Manganese, Nickel and zinc) and toxic (Cd and Pb) heavy metals content of herbal preparations sold in Kurmi market of Kano state, Nigeria was carried out. The aim of this study is to evaluate the levels of essential and toxic heavy metals in Kano herbal preparations used for commonly identified disease conditions. The samples were digested by wet digestion method with nitric acid and perchloric acids and analyzed using Flame Atomic Absorption Spectrometer (FAAS). The data obtained were statistically treated and the results presented as mean of three replicated. The range of mean concentrations of the essentials Cu, Co, Fe, Mn, Ni, Zn and toxic Cd, Pb heavy metals obtained were 4.94-10.03μg/g, 3.33-3.80μg/g, 163.04-350.95 μg/g, 57.57-65.05μg/g, 9.94-15.63μg/g,, 6.86-66.59 μg/g and 1.53-3.23μg/g, 3.75-35.24 μg/g respectively. The level of contamination of the herbal preparation with the toxic heavy metals indicated 100% of the samples analyzed contained cadmium above WHO permissible limits (0.3μg/g) specified for herbal medicine and 33% of the samples contained lead (Pb) above WHO permissible limits (10μg/g) specified for herbal medicine. The gross level of contamination of these herbal preparations with Pb and Cd metals could be associated to poor adherence to quality control requirements such as current/good manufacturing practice (CGMP) and effective surveillance/enforcement. There is need for commitment for immediate action by both the herbal medicine practitioners and the relevant stakeholders in order to avert impending health hazards due to the tendency of gradual accumulation of these toxic metals in the body system of the consumers of these herbal preparations in order to attain to safe and effective herbal medicine usage in Nigeria.Keywords: Disease conditions, Heavy metals, Herbal preparations, Kan