Modeling and optimization of trivalent arsenic removal from wastewater using activated carbon produced from maize plant biomass: a multivariate experimental design approach

This research article was published by Springer Nature Limited in 2023Globally, both industrialized and developing nations struggle with the issue of water pollution due to heavy metals. Human life depends on water, and when it is contaminated with dangerous heavy metals like arsenic, people’s health suffers. The interactive influence of three independent sorption processes variables such as bio-adsorbent dosage (0.50–3.00 g/L), contact time (40.00–90.00 min), and initial concentration (10.00–30.00 mg/L) on the modeling and optimization of trivalent arsenic removal from wastewater was studied in a batch mode using multivariate experimental design. The quadratic models provided accurate predictions for the response variables with high coefficients of correlation of 0.9984 and 0.9994 for removal and uptake rates, respectively. The developed models were accurate and exhibited a remarkable correlation between the observed and projected data according to the diagnostic test analyses. Through the analysis of variance, all the studied adsorption factors were statistically significant (p-values < 0.0001) with initial concentration and bio-adsorbent dosage producing the main interactive effect on the percentage removal and adsorption capacity with F-values of 146.05 and 264.65, respectively. The optimum operating conditions attained were 90.00 min contact time, 0.50 g/L bio-adsorbent dosage, and an initial concentration of 10.00 mg/L, which gave arsenic maximum removal and uptake efficiencies of 93.14% and 7.04 mg/g, correspondingly with the desirability of 0.844. Confirmative tests were conducted under the optimized conditions to validate the accuracy of the models in which a maximum removal efficacy of 94.33% and adsorption capacity of 7.15 mg/g were achieved. The applicability of the bio-adsorbent in the adsorption of arsenic in textile industrial wastewater was also tested and the bio-adsorbent could competitively decontaminate over 99% of arsenic species from the wastewater

Non-competitive and competitive detoxification of As (III) ions from single and binary biosorption systems and biosorbent regeneration

This research article was published by Springer Nature Switzerland AG. in 2023The quantity of studies reporting on single-metal sorption systems is increasing every day while the elimination of heavy metals in binary and multisolute systems is seldom reported. Therefore, the biosorption and desorption of arsenic from single and binary systems on hybrid granular activated carbon have been investigated using the batch technique. The hybrid granular activated carbon was characterized using Fourier transform infrared spectrometer and Brunauer–Emmett–Teller, and the results showed that the biosorbent surface characteristics could facilitate arsenic removal from the non- and competitive biosorption media. The main biosorption mechanisms of arsenic on the biosorbent involved surface complexation, electrostatic attraction, and replacement of hydroxyl groups. Furthermore, the effective elimination of arsenic was discovered to be reliant on the sorbent’s physicochemical properties as well as all the studied independent biosorption factors. The equilibrium sorption data of both the single and binary systems were best explained by the Langmuir and pseudo-second-order models, indicating the mechanism of arsenic biosorption was mainly chemisorption. The Langmuir maximum monolayer sorption capacities of the biosorbent were 205.76 and 153.09 mg/g for the single and binary systems, respectively. While the evaluated thermodynamic parameters suggest that the biosorption removal of arsenic from both sorption systems was spontaneous and endothermic with increasing randomness at the liquid–solid interface, the successive biosorption–desorption studies indicated that the exhausted biosorbent can be renewed without a substantial deterioration in its uptake capacity even after the seventh regeneration cycle. This indicates that the biosorbent has the economic potential to be used repeatedly in arsenic species sequestration from wastewater

Removal of heavy metals from binary and multicomponent adsorption systems using various adsorbents – a systematic review

This research article was published in Journals Research Society of Chemistry Volume13, Issue19,2023The ecosystem and human health are both significantly affected by the occurrence of potentially harmful heavy metals in the aquatic environment. In general, wastewater comprises an array of heavy metals, and the existence of other competing heavy metal ions might affect the adsorptive elimination of one heavy metal ion. Therefore, to fully comprehend the adsorbent's efficiency and practical applications, the abatement of heavy metals in multicomponent systems is important. In the current study, the multicomponent adsorption of heavy metals from different complex mixtures, such as binary, ternary, quaternary, and quinary solutions, utilizing various adsorbents are reviewed in detail. According to the systematic review, the adsorbents made from locally and naturally occurring materials, such as biomass, feedstocks, and industrial and agricultural waste, are effective and promising in removing heavy metals from complex water systems. The systematic study further discovered that numerous studies evaluate the adsorption characteristics of an adsorbent in a multicomponent system using various important independent adsorption parameters. These independent adsorption parameters include reaction time, solution pH, agitation speed, adsorbent dosage, initial metal ion concentration, ionic strength as well as reaction temperature, which were found to significantly affect the multicomponent sorption of heavy metals. Furthermore, through the application of the multicomponent adsorption isotherms, the competitive heavy metals sorption mechanisms were identified and characterized by three primary kind

Adsorption and desorption ability of divalent mercury from an interactive bicomponent sorption system using hybrid granular activated carbon

This research article was published in Environmental Monitoring and Assessment, Volume 195, 2023.The sequestration of heavy metals from multicomponent sorption media has become critical due to the noxious effects of heavy metals on the natural environment and subsequently on human health as well as all life forms. The abatement of heavy metals using bio-adsorbents is one of the efficient and affordable approaches for treating water and wastewater. Therefore, the interactive effect of arsenic [As(III)] ions on the sorption and desorption ability of mercury [Hg(II)] from a binary sorption system was conducted. More so, the impact of reaction time, solution pH, bio-adsorbent particle size, bio-adsorbent dose, initial mono-metal, and binary-metal concentration as well as reaction temperature on the individual and competitive sorption of Hg(II) was explored. The study showed that Hg(II) could be removed effectively from the single-component system and competitively from the aqueous phases by the bio-adsorbent in the coexistence of As(III) species in the bicomponent medium. The adsorptive detoxification of Hg(II) from the monocomponent and bicomponent sorption media showed dependence on all the studied adsorption parameters. The occurrence of As(III) species in the bicomponent sorption medium affected the decontamination of Hg(II) by the bio-adsorbent and the major interactive mechanism was found to be antagonism. The spent bio-adsorbent was effectively recycled using 0.10 M nitric (HNO3) and hydrochloric (HCl) acids solutions and the multi-regeneration cycles showed a high removal efficiency in each cycle. The first regeneration cycle was found to have the highest Hg(II) ions removal efficiencies of 92.31 and 86.88% for the monocomponent and bicomponent systems, respectively. Thus, the bio-adsorbent was found to be mechanically stable and reusable up to the 6.00 regeneration cycle. Therefore, this study concludes that the bio-adsorbent not only has a higher adsorption capacity but also a good recycling performance pointing to good industrial applications and economic prospects

A comprehensive review on the decontamination of lead(II) from water and wastewater by low-cost biosorbents

This research article published by Royal Society of Chemistry, 2022The disadvantages of conventional methods in water and wastewater management including the demand for high energy consumption, the creation of secondary toxic sludge, and operation cost are much too high for developing countries. However, adsorption using low-cost biosorbents is the most efficient nonconventional technique for heavy metals removal. The high adsorption capacities, cost-effectiveness, and the abundance of agricultural waste materials in nature are the important parameters that explain why these biosorbents are economical for heavy metals removal. The present investigation sought to review the biosorption of lead [Pb(II)] onto low-cost biosorbents to understand their adsorption mechanism. The review shows that biosorption using low-cost biosorbents is eco-friendly, costeffective, and is a simple technique for water and wastewater treatment containing lead(II) ions. The batch biosorption tests carried out in most studies show that Pb(II) biosorption by the low-cost biosorbents is dependent on biosorption variables such as pH of the aqueous solution, contact time, biosorbent dose, Pb(II) initial concentration, and temperature. Furthermore, batch equilibrium data have been explored in many studies by evaluating the kinetics, isothermal and thermodynamic variables. Most of the studies on the adsorptive removal of Pb(II) were found to follow the pseudo-second kinetic and Langmuir isotherm models with the thermodynamics variables suggesting the feasibility and spontaneous nature of Pb(II) sequestration. However, gaps exist to increase biosorption ability, economic feasibility, optimization of the biosorption system, and desorption and regeneration of the used agricultural biosorbents

Applicability of bio-adsorbents synthesized from maize/corn plant residues for heavy metals removal from aquatic environments: an insight review

The underutilization of agricultural waste products in recent years has resulted in environmental issues owing to improper disposal. As a result, heavy metals removal from aqueous systems utilizing sorbent materials produced from agricultural wastes has received a lot of attention. The current study provides an insightful review of the use of bio-adsorbents synthesized from maize/corn residues to decontaminate various toxicants from wastewater. Although bio-adsorbents made from maize/corn residues have shown to be efficient in the sequestration of heavy metals from wastewater, no study has looked at hybrid bio-adsorbents made from various parts of the maize/corn plant. Moreover, all studies practically investigate the sorption processes using the one-factor design technique, which exceedingly consumes time and is expensive for a significant number of biosorption/adsorption factors. Besides, the majority of the studies used bio-adsorbents produced from maize/corn biomass to remove heavy metals from single sorption systems. Furthermore, very few studies have focussed on heavy metals desorption from the exhausted maize/corn bio-adsorbents following the adsorption process to recycle the spent bio-adsorbents for future usage, which would be more cost-effective. Based on the gaps revealed in this review, it is recommended that further investigations on the usefulness of bio-adsorbents derived from maize/corn biomass in cleansing different water toxicants should be carried out

Artisanal and small-scale mining in Tanzania and health implications: A policy perspective

The mineral sector, especially its small-scale subsector, has become significant in the emerging economies of the Global South. Tanzania is the focus of this policy exposition paper because, aside from Ghana and South Africa, Tanzania is ranked 4th in Africa in terms of its mineral deposits and small-scale mining activities. The focus is also on artisanal and small-scale mining (ASM) because ASM operations have significantly increased in recent times across this mineral-rich country of East Africa. This is done against a negative backdrop-labelling of ASM as unsustainable, environmentally unfriendly, inefficient, and illegal. Tanzania has made some progress to respond to some of the challenges in the mining sector to improve the micro and macroeconomics of the country. Some areas remain challenging including the lack of proper environmental health education for the ASM miners; the lack of clear national-level policies to guide health-related matters in the ASM subsector, and the small capital investment of the ASM subsector to support healthy mining practices. The details related to the persistence of these challenges are not well known, particularly those that pertain to policymaking. This article attempts to evaluate the policy environment of the ASM subsector in Tanzania and propose appropriate actions for the future of mineral resource policymaking in Tanzania