Nuhu Dalhat Mu’azu

Electrochemical oxidation of low phenol concentration on boron doped diamond anodes: optimization via response surface methodology

AbstractDirect electrochemical oxidation of aqueous organic pollutants using Boron doped diamond (BDD) electrode is usually inhibited at low concentration of the target organic pollutant. In this study, a multivariate statistical approach was used to optimize the direct electrochemical oxidation of low phenol concentration using on BDD anodes by employing response surface methodology (RSM) technique. A 24 factorial faced centered central composite design was employed for the experimental design from which the influences of operating parameters were assessed using analysis of variance. The efficiencies of removal of phenol, total organic carbon and chemical oxygen demand, the percentage of aromatic byproducts produced, current efficiency, and energy consumed were collectively taking into account in the RSM optimization. All the six responses fitted quadratic models (R2 of 83.21–98.48%) with the relative contributions of the investigated parameters on the responses following the order: reaction time > pH > ...

Application of Box-Behnken Design to Hybrid Electrokinetic-Adsorption Removal of Mercury from Contaminated Saline-Sodic Clay Soil

A hybrid electrokinetic-adsorption (HEKA) technique using uniform electric field and granular activated carbon (GAC) produced from date palm pits was investigated for the removal of mercury from natural saline-sodic clay heavily contaminated with heavy metals, phenol, and kerosene. Response surface methodology (RSM) was employed to model, optimize, and interpret the results obtained with the aid of Design Expert software. According to the Box-Behnken experimental design, 15 experiments were conducted each with residence time of three weeks. The effects of voltage gradient (0.2–1 V/cm), initial Hg concentration (mg/Kg), and polarity reversal interval (0-48 hours) on Hg removal efficiency and energy consumed for Hg removal were investigated. Respectively, the responses fitted reduced cubic (R2 = 99.3%) and quadratic models (R2 = 92.3%) with the overall relative contributions of the investigated parameters on the responses following the order: voltage gradient > initial Hg concentration > polarity reversal interval based on analysis of variance (ANOVA). The optimal conditions obtained with desirability of 90% aimed at maximizing Hg removal were 24 hours polarity reversal interval, 0.2 V/cm voltage gradient, and 100 mg/kg initial Hg concentration. This optimum operating condition yielded good removal of Hg (99.5%) at reduced energy consumption of 50.1kWh.m−3mg−1. Experimental validation of the models showed good prediction of Hg removal efficiency (0.0368% prediction error). The results presented herein suggest that HEKA technology could be utilized effectively for the removal of Hg from contaminated, low permeable soils under extreme soil and contamination conditions.

Polyaspartate extraction of cadmium ions from contaminated soil: Evaluation and optimization using central composite design

The occurrences of heavy metal contaminated sites and soils and the need for devising environmentally friendly solutions have become global issues of serious concern. In this study, polyaspartate (a highly biodegradable agent) was synthesized using L-Aspartic acid via a new modified thermal procedure and employed for extraction of cadmium ions (Cd) from contaminated soil. Response surface methodology approach using 35 full faced centered central composite design was employed for modeling, evaluating and optimizing the influence of polyaspartate concentration (36-145mM), polyaspartate/soil ratio (5-25), initial heavy metal concentration (100-500mg/kg), initial pH (3-6) and extraction time (6-24h) on Cd ions extracted into the polyaspartate solution and its residual concentration in the treated soil. The Cd extraction efficacy obtained reached up to 98.8%. Increase in Cd extraction efficiency was associated with increase in the polyaspartate and Cd concentration coupled with lower polyaspertate/soil ratio and initial pH. Under the optimal conditions characterized with minimal utilization of the polyaspartate and high Cd ions removal, the extractible Cd in the polyaspartate solution reached up to 84.4mg/L which yielded 85% Cd extraction efficacy. This study demonstrates the suitability of using polyaspartate as an effective environmentally friendly chelating agent for Cd extraction from contaminated soils.

Removal of Phenolic Compounds from Water Using Sewage Sludge-Based Activated Carbon Adsorption: A Review

Due to their industrial relevance, phenolic compounds (PC) are amongst the most common organic pollutants found in many industrial wastewater effluents. The potential detrimental health and environmental impacts of PC necessitate their removal from wastewater to meet regulatory discharge standards to ensure meeting sustainable development goals. In recent decades, one of the promising, cost-effective and environmentally benign techniques for removal of PC from water streams has been adsorption onto sewage sludge (SS)-based activated carbon (SBAC). This is attributed to the excellent adsorptive characteristics of SBAC and also because the approach serves as a strategy for sustainable management of huge quantities of different types of SS that are in continual production globally. This paper reviews conversion of SS into activated carbons and their utilization for the removal of PC from water streams. Wide ranges of topics which include SBAC production processes, physicochemical characteristics of SBAC, factors affecting PC adsorption onto SBAC and their uptake mechanisms as well as the regeneration potential of spent SBAC are covered. Although chemical activation techniques produce better SBAC, yet more research work is needed to harness advances in material science to improve the functional groups and textural properties of SBAC as well as the low performance of physical activation methods. Studies focusing on PC adsorptive performance on SBAC using continuous mode (that are more relevant for industrial applications) in both single and multi-pollutant aqueous systems to cover wide range of PC are needed. Also, the potentials of different techniques for regeneration of spent SBAC used for adsorption of PC need to be assessed in relation to overall economic evaluation within realm of environmental sustainability using life cycle assessment.

Highly efficient removal of Pb(II) ion from aqueous phase using surface modified graphene. Equilibrium and kinetic study

A novel surface-modified graphene (SMG) was employed as an adsorbent for the removal of Pb(II) from aqueous solution at room temperature (295 ± 5 K). The SMG was prepared from graphene (G) via oxidation method using concentrated nitric acid. scanning electron microscopy, thermogravimetric analysis, Brunauer, Emmett, and Teller, and Fourier transform infrared spectroscopy were used to characterize the produced adsorbent. Batch adsorption experiments were carried out under different operating conditions; pH (2–7), adsorbent dosage (4–32 mg), and contact time (5–240 min). The maximum Pb(II) adsorption was obtained at a pH of 6, adsorbent dose of 20 mg after 100 min at 298 K. Surface of the SMG had more oxygen functionalities and higher surface area compared with the G, thereby resulting in enhanced removal of Pb(II), significantly. Pseudo-second-order kinetic model fitted the results better than pseudo-first-order and intra-particle diffusion models. Redlich– Peterson, Freundlich, and Langmuir isotherm models fitted very well the equilibrium results. The SMG was a superior adsorbent for Pb(II) with a maximum adsorption capacity of 140 mg/g. Therefore, it can be concluded that SMG can be effectively used to remove heavy metals from waste and domestic water.