Performance Comparison of Chemically Modified Sugarcane Bagasse for Removing Cd(II) in Water Environment

This paper evaluates the adsorption capacity of chemically sugarcane bagasses with sodium hydroxide(SHS),citric acid(CAS),tartaric acid(TAS)and unmodified sugarcane bagasse(SB)for cadmium adsorption in water environment.The results prove adsorption capacity for Cd(II)increases after chemical modification and the adsorption fits perfectly with the Langmuir isotherm.CAS had the highest maximum adsorption capacity of 45.45 mg/g followed by TAS with 38.46 mg/g and SHS with 29.41 at optimum pH 5.0 and 120 minutes equilibrium time while 1 g SB removed 18.8 mg Cd(II)in the same conditions.The kinetics study of the process followed a pseudo-secondorder rate expression,that indicated a strong interaction between the biosorbents and adsorbate.The sugarcane bagasse and modified sugarcane bagasse were characterized by scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR)analysis.The chemical modification was confirmed by the presence of carboxyl and esters groups created at 1,738 cm-1.The estimation of acid groups in modified materials shows the enhancement of this group after modification.On the other hand,desorption studies showed the high leaching of cadmium ion from the biosorbent leading to the efficient reutilization of materials.

<i>Acacia etbaica</i>as a Potential Low-Cost Adsorbent for Removal of Organochlorine Pesticides from Water

The presence of pesticides in the environment is of great concern due to their persistent nature and chronic adverse effect on human health and the environment. Water bodies are subject to pollution by organochlorine pesticides, especially in developing countries, where water pollution is a key sustainability challenge. Hence, activated carbon is considered a universal adsorbent for the removal of organochlorine pollutants from water. Activated carbon from Acatia etbaica was prepared using traditional kilns with low investment costs. Pesticides such as aldrin, dieldrin and DDT were selected for adsorption because of their common usage in agricultural and malaria control activities and may occur in high concentrations in surface waters that are used as drinking water sources. The effect of the adsorbent dose and initial concentration were investigated. To describe the equilibrium isotherms the experimental data were analyzed by the Langmuir and Freundlich isotherm models. The Freundlich model gave the best correlation with the experimental data. Activated carbon prepared from Acacia etbaica was found to be an effective and low-cost alternative for the removal of organochlorine pesticides from aqueous solutions. The preparation method allows the use of this material by local communities for effective remediation of pollution by pesticides.

Determination of the Toxicological Risk of Urban Waste from the City of Uvira Dumped into the North-Western Coast in Lake Tanganyika (Democratic Republic of Congo)

This study focuses on determining the toxicological risks of urban waste from the city of Uvira, discharged into Lake Tanganyika, on the surrounding population. Volatile organic compounds were measured in a variety of solid waste matrices, including inorganic micropollutants in wastewater and fish. The concentrations of Hg and Pb in the lake were found to be 1.21 and 1.42 μg/L respectively and between 0.83 to 18.36 μg/L of Hg and 8.25 to 670 μg/L of Pb, at the collector outlet. The presence of trace metallic elements, such as Cr, Co, Ni, Cu, Zn, As, Sb, Hg and Pb, were detected at high concentrations compared to the WHO standard. An ecotoxicology experiment herein on wastewater samples showed lethal pollutant concentrations of the order of 0.0055 mL/mL which killed at least 50% of fish (LC50), confirming the toxicity of the wastewater. These potentially harmful effluents also contain volatile organic compounds originating in high concentration from the pharmaceutical discharges of the general Uvira hospital, in particular: toluene, ethylbenzene, m-xylene/p-xylene, o-xylene and chloroform in higher concentrations compared to the norm. Other components such as benzene, bromodichloroethane and 1,1-dichloroethane were found to be present, but at a concentration below 0.05 ppb. A variety of trace organics can be suspected to be present as well.

Membrane bioreactors for hospital wastewater treatment: recent advancements in membranes and processes

Discharged hospital wastewater contains various pathogenic microorganisms,antibiotic groups,toxic organic compounds,radioactive elements,and ionic pollutants.These contaminants harm the environment and human health causing the spread of disease.Thus,effective treatment of hospital wastewater is an urgent task for sustainable development.Membranes,with controllable porous and nonporous structures,have been rapidly developed for molecular separations.In particular,membrane bioreactor(MBR)technology demonstrated high removal efficiency toward organic compounds and low waste sludge production.To further enhance the separation efficiency and achieve material recovery from hospital waste streams,novel concepts of MBRs and their applications are rapidly evolved through hybridizing novel membranes(non hydrophilic ultrafiltration/microfiltration)into the MBR units(hybrid MBRs)or the MBR as a pretreatment step and integrating other membrane processes as subsequent secondary purification step(integrated MBR-membrane systems).However,there is a lack of reviews on the latest advancement in MBR technologies for hospital wastewater treatment,and analysis on its major challenges and future trends.This review started with an overview of main pollutants in common hospital wastewater,followed by an understanding on the key performance indicators/criteria in MBR membranes(i.e.,solute selectivity)and processes(e.g.,fouling).Then,an in-depth analysis was provided into the recent development of hybrid MBR and integrated MBR-membrane system concepts,and applications correlated with wastewater sources,with a particular focus on hospital wastewaters.It is anticipated that this review will shed light on the knowledge gaps in the field,highlighting the potential contribution of hybrid MBRs and integrated MBRmembrane systems toward global epidemic prevention.

Surface modification of HKUST-1 for enhanced activity of immobilized formate dehydrogenase used in CO_(2)hydrogenation

Post synthetic modification of a hydrophilic metal-organic framework(MOF),HKUST-1,with stearic acid(SA)was carried out to enhance the stability of HKUST-1 in aqueous solution to be used as a support for formate dehydrogenase(FDH)used for CO_(2)conversion to formate.SA modification improved the hydrophobicity without affecting the morphology and crystal structure of MOF.Adsorption of FDH on the modified MOF(SA@HKUST-1)was compared to that of the native HKUST-1 and ZIF-L.The adsorption kinetics on all MOFs was found to follow pseudo-second order kinetics and the isotherm was best described by Freundlich model.The high stability of SA@HKUST-1 and enhanced hydrophobic interaction between support and CO_(2)resulted in high catalytic efficiency and stability of FDH@SA@HKUST-1.The immobilized enzyme retained 95.1%of its initial activity after 4 cycles of repeated use.It was also shown that FDH@SA@HKUST-1 retained morphology and crystal structure after repeated use.Results of the present work provide novel insight into the influence of hydrophobic MOFs on the activity and stability of immobilized FDH.These findings are expected to assist in developing highly active and stable biocatalysts for CO_(2)hydrogenation at commercial level.

Comparative studies on fouling of homogeneous anion exchange membranes by different structured organics in electrodialysis

Five negatively charged organic compounds with different structures, sodium methane sulfonate(MS), sodium benzene sulfonate(BS), sodium 6-hydroxynaphthalene-2-sulfonate(NSS), sodium dodecyl sulfate(SDS), and sodium dodecyl benzene sulfonate(SDBS), were used to examine the fouling of an anion exchange membrane(AEM) in electrodialysis(ED),to explore the effect of molecular characteristics on the fouling behavior on the AEM and changes in the surface and electrochemical properties of the AEM. Results indicated that the fouling degree of the AEM by the different organics followed the order:SDBS > SDS > NSS > BS > MS. SDBS and SDS formed a dense fouling layer on the surface of the AEM, which was the main factor in the much more severe membrane fouling, and completely restricted the transmembrane ion migration. The other three organics caused fouling of the AEM by adsorption on the surface and/or accumulation in the interlayer of the AEM, and exhibited almost no influence on the transmembrane ion migration. It was also concluded that the organics with benzene rings caused more severe fouling of the AEM due to the stronger affinity interaction and steric effect between the organics and the AEM compared with organics with aliphatic chains.