Adsorption of heavy metals from coal acid mine drainage by shrimp shell waste: Isotherm and continuous-flow studies

The main characteristics of coal acid mine drainage (AMD) are low pH and high concentrations of sulfate and different metallic ions. The objective of this research was to study the sorption equilibrium of the removal of metal ions and acids present in coal AMD using shrimp shell in natura (SS) as a biomaterial as well as the behavior of the continuous-flow removal process. The isotherms assays were carried out with synthetic solutions and natural AMD aiming to identify significant differences on metals ions removal by SS. Five isotherm models were studied. R2 values and error statistical functions studies showed that the Freundlich isotherm model was the most appropriate for fitting the experimental data with both synthetic solutions and natural AMD, indicating a metallic removal via a physisorption mechanism. The removal of metal ions in continuous descendent flow was up to 90% Fe and 88% Mn, and the pH increased from 3.49 to 6.77. The adsorption capacities of Fe and Mn resulted in 17.43 and 3.87 mg g−1 SS, respectively. Computing chemical modelling (Visual MINTEQ® software) indicated the sorption was a predominant mechanism on AMD remediation with SS, but with high pH-dependence. This study confirms the suitability of the proposed treatment and provides valuable information for designing a low-cost remediation process for AM

Aplication of the statistical experimental design to optimize mine-impacted water (MIW) remediation using schrimp-shell

Mine-impacted water (MIW) is one of the most serious mining problems and has a high negative impact on water resources and aquatic life. The main characteristics of MIW are a low pH (between 2 and 4) and high concentrations of SO42− and metal ions (Cd, Cu, Ni, Pb, Zn, Fe, Al, Cr, Mn, Mg, etc.), many of which are toxic to ecosystems and human life. Shrimp shell was selected as a MIW treatment agent because it is a low-cost metal-sorbent biopolymer with a high chitin content and contains calcium carbonate, an acid-neutralizing agent. To determine the best metal-removal conditions, a statistical study using statistical planning was carried out. Thus, the objective of this work was to identify the degree of influence and dependence of the shrimp-shell content for the removal of Fe, Al, Mn, Co, and Ni from MIW. In this study, a central composite rotational experimental design (CCRD) with a quadruplicate at the midpoint (22) was used to evaluate the joint influence of two formulation variables—agitation and the shrimp-shell content. The statistical results showed the significant influence (p < 0.05) of the agitation variable for Fe and Ni removal (linear and quadratic form, respectively) and of the shrimp-shell content variable for Mn (linear form), Al and Co (linear and quadratic form) removal. Analysis of variance (ANOVA) for Al, Co, and Ni removal showed that the model is valid at the 95% confidence interval and that no adjustment needed within the ranges evaluated of agitation (0–251.5 rpm) and shrimp-shell content (1.2–12.8 g L−1). The model required adjustments to the 90% and 75% confidence interval for Fe and Mn removal, respectively. In terms of efficiency in removing pollutants, it was possible to determine the best experimental values of the variables considered as 188 rpm and 9.36 g L−1 of shrimp-shell

Optimization of Fe and Mn Removal from Coal Acid Mine Drainage (AMD) with Waste Biomaterials: Statistical Modeling and Kinetic Study

The main characteristics of coal acid mine drainage (AMD) are a low pH and high concentrations of sulfate and diferent metallic ions. Response surface methodology using the central composite rotatable design (CCRD) model was used to optimize the parameters for AMD remediation with aquaculture farming waste [shrimp shell (SS) and mussel byssus (MB)]. SS was chosen due to its high chitin (a metal sorbent) and calcium carbonate (an acidity neutralizing agent) content, and MB because of its potential synergistic efect for the treatment. The coefcient of determination and standard error results from the analysis of variance have shown the model to be adequate. The predicted values were in good agreement with the experimental values. The best experimental conditions established from the statistical study were 136 rpm, 11.46 g L−1 SS and 71.6 g L−1 MB. CCRD can efciently be applied for modeling the AMD remediation with biomaterials and is an economical way of obtaining the maximum amount of information in a short period of time with the fewest number of experiments. Additionally, fve kinetic models, i.e., pseudo-frst-order, pseudo-second-order, intraparticle difusion, Bangham and Elovich equation, were tested to investigate the adsorption mechanisms. The kinetic studies revealed that a 200 min contact time is sufcient to transform AMD into water suitable for non-potable reuse. The pseudo-second-order model provided the best ftting of the experimental data, indicating a chemical adsorption mechanism. This research shows the suitability of the proposed treatment, and the information is valuable for designing a low-cost remediation process for AM

Chitin as a substrate for the biostimulation of sulfate-reducing bacteria in the treatment of mine-impacted water (MIW)

This study aims to know the basis of sulfate-reducing bacteria (SRB) and chitin source relationship for the development of a biotreatment system for mine-impacted water (MIW). The MIW consists of river water impacted by coal acid mine drainage (AMD), an extremely acid effluent, rich in sulfate and dissolved metal ions, with a high pollutant potential. Chitin was used as metal ion sorbent and biostimulant of SRB, whose anaerobic dissimilatory metabolism reduces sulfate to sulfide. Microcosms were built in an oxygen-free atmosphere using chitin from two different sources: commercial chitin and shrimp shell waste, which contains calcium carbonate, an acidity removal agent, in addition to chitin. The results indicate that the shrimp shell performs best in removing sulfate (99.75%), iron (99.04%), aluminum (98.47%), and manganese (100%) ions. The iron ion sorption kinetics of the sediments were also studied; pseudo-second order behavior was observed. Highthroughput sequencing analysis revealed the present bacterial community and its abundance in the microcosms after 11 and 30 treatment days: SRB were detected but were not the majority. Thus, this research aims to contribute to the sustainable treatment MIW through the employment of an abundant and low-cost biomateria

Potencial dos resíduos do processamento de camarão para remediação de águas contaminadas com drenagem ácida mineral

Resumo A drenagem ácida mineral (DAM) é um dos mais graves impactos ambientais da mineração. Cursos de água impactados pela DAM são avaliados como impróprios acarretando graves impactos ambientais e problemas socioeconômicos severos. Este estudo visa identificar o potencial de um resíduo, casca de camarão, como fonte de quitina e alcalinidade para remediação de águas contaminadas por DAM visando seu posterior reuso para fins secundários não potáveis. Foram efetuados ensaios com a casca de camarão, diferenciando entre corpo (CR) e cabeça (CB), e quitina comercial (QT, 70% de pureza), para o tratamento de amostras de água superficiais e subterrâneas impactadas da Região Carbonífera Catarinense/SC (Brasil). Realizaram-se ensaios em duplicata e em regime de batelada variando o teor de substrato, tempo de contato e velocidade de agitação. Conseguiu-se a remoção quase total de Fe (>92%) e Al (>99%) e uma remoção de Mn entre 40-60%. CR apresentou os melhores resultados após 48h de tratamento com 200 rpm e 10 gL–1de substrato. O aumento no pH foi mais significativo nas amostras contendo CR, passando o pH de ~3 para ~7. Os resultados indicaram o potencial da utilização direta da casca de camarão para o tratamento de efluentes para reuso secundário não potável

Determination of zinc and cadmium with characterized Electrodes of carbon and polyurethane modified by a bismuth film

This study aims to use electrodes modified with bismuth films for the determination of zinc and cadmium. The film was electrodeposited ex situ on a composite carbon electrode with polyurethane and 2% metallic bismuth (2BiE) and on a carbon bar electrode (CBE). The electrodes were characterized by scanning electron microscopy and energy dispersive spectroscopy. Through differential pulse anodic stripping voltammetry, the electrodes 2BiE and CBE containing bismuth films showed a limit of detection (LOD) of 5.56 × 10-5 and 3.07 × 10-5 g.L-1 for cadmium and 1.24 × 10-4 and 1.53 × 10-4 g.L-1 for zinc, respectively. The presence of a bismuth film increased the sensitivity of both electrodes

Use of a Waste-Derived Linde Type-A Immobilized in Agarose for the Remediation of Water Impacted by Coal Acid Mine Drainage at Pilot Scale

A new adsorbent based on an immobilized waste-derived LTA zeolite in agarose (AG) has proven to be an innovative and efficient alternative for removing metallic contaminants from water impacted by acid mine drainage (AMD) because the immobilization prevents the solubilization of the zeolite in acidic media and eases its separation from the adsorbed solution. A pilot device was developed containing slices of the sorbent material [AG (1.5%)&ndash;LTA (8%)] to be used in a treatment system under an upward continuous flow. High removals of Fe2+ (93.45%), Mn2+ (91.62%), and Al3+ (96.56%) were achieved, thus transforming river water heavily contaminated by metallic ions into water suitable for non-potable use for these parameters, according to Brazilian and/or FAO standards. Breakthrough curves were constructed and the corresponding maximum adsorption capacities (mg/g) (Fe2+, 17.42; Mn2+, 1.38; Al3+, 15.20) calculated from them. Thomas mathematical model was well fitted to the experimental data, indicating the participation of an ion-exchange mechanism in the removal of the metallic ions. The pilot-scale process studied, in addition to being highly efficient in removing metal ions at toxic levels in AMD-impacted water, is linked to the sustainability and circular economy concepts, due to the use as an adsorbent of a synthetic zeolite derived from a hazardous aluminum waste