N.A. Oladoja

Snail shell as coagulant aid in the alum precipitation of malachite green from aqua system

The ability of snail shell (SS) to act as coagulant aid in the alum precipitation of a basic dye (MG) was investigated. The proximate physicochemical characterization of the SS showed the pH(solution) to be 8.01, high fraction of the inorganic constituents (ash content=93.76%), the presence of Ca(2+) (99.74%) as the major metal ion present and the point zero charge (PZC) found at pH 7.9. The X-ray diffractometric analysis revealed the presence of aragonite. The stability and leaching of the SS, tested in different aqua medium (acidic, basic and neutral solutions) showed that the SS was less stable in the acidic medium. Both the alum and the SS were used, differently, for the dye precipitation. The alum alone had no precipitating effect on the MG dye molecules while SS alone was able to reduce the intensity of the dye. When the SS was used as coagulant aid in alum precipitation, the percentage of the MG molecule removed was enhanced. The effects of some process variables (coagulant/coagulant aid dosage, pH and flocculation time) were optimized by method of continuous variation. The optimum pH for the MG removal was found to range between 4 and 5 but the amount of MG removed was appreciable at all the pH studied. Studies on the effect of time on the flocculation of the precipitated MG molecule showed that the problem of redispersion and restabilisation encountered in alum precipitation could be overcome using alum-SS combination. The settling characteristics of the sludge obtained from the use of SS alone and alum-SS combination was studied by measuring the sludge volume index (SVI, mg/g) over time. The value of the SVI (mg/g) showed that the sludge produced from the alum-SS combination had better settling characteristics than the sludge got from the use of SS alone.

Competitive modeling for the biosorptive removal of copper and lead ions from aqueous solution by Mansonia wood sawdust

Mansonia wood sawdust is applied as a biosorbent for the removal of copper and lead ions from single and binary aqueous solution. The effect of solution pH, electrolyte, metal ion competition and temperature were examined to obtain insight of its application for industrial waste water treatment. The Langmuir isotherm provided a better fit to experimental data for lead ion sorption with a higher monolayer capacity, while copper ion sorption was best described by the Freundlich and BET isotherms. The combined effect of adsorbing one metal ion in the presence of the other metal ion reduced the adsorption capacity of either metal ion. In a binary solution, removal of lead ions in the presence of copper ions followed the Langmuir isotherm model while the removal of copper ions in presence of lead ions followed both the Langmuir and BET isotherm models.

Preparation of magnetic, macro-reticulated cross-linked chitosan for tetracycline removal from aquatic systems

A novel adsorbent, magnetic, macro-reticulated cross-linked chitosan (MRC) was synthesised for the removal of tetracycline (TC) from water using a source of biogenic waste (gastropod shells) as a pore-forming agent. The insertion of crosslinks into the chitosan frame was confirmed by FTIR analysis, while the stability of the MRC was demonstrated via a stability test performed in an acidic solution. The enhanced porosity of the MRC was confirmed by the evaluation of its porosity, a swelling test and the determination of its specific surface area. The time-concentration profile of the sorption of TC onto the MRC demonstrated that equilibrium was attained relatively quickly (120 min), and the data obtained fitted a pseudo second order (r(2)>0.99) kinetic equation better than a pseudo first order or reversible first order kinetic equation. The optimisation of process variables indicated that the sorption of TC onto the MRC was favoured at a low solution pH and that the presence of organics (simulated by the addition of humic acid) negatively impacted the magnitude of TC removal. The area of coverage of TC on the MRC (2.51 m(2)/g) was low compared to the specific surface area of the MRC (47.95 m(2)/g). The value of the calculated energy of adsorption of TC onto the MRC was 100 kJ/mol, which is far above the range of 1-16 kJ/mol stipulated for physical adsorption.

Evaluation of snail shell as a coagulant aid in the alum precipitation of aniline blue from aqueous solution.

The present studies aimed to evaluate the potential of snail shell (SS) as a coagulant aid in the alum precipitation of aniline blue (AB), an acid dye, from an aqueous system. The proximate physico‐chemical characteristics of the SS were determined, and the results obtained showed that the pHsolution was 8.01, the SS was made up of a high fraction of inorganic constituents (ash content of 93.76%), Ca2+ was present as the major metal ion (99.74%), and the point of zero charge (PZC) was found to be at pH 7.9. The mineralogical assemblage was studied using an X‐ray diffractometer, and the results obtained revealed the presence of aragonite. The stability and leaching of the SS, tested in different aqueous media (acidic, basic and neutral solutions) showed that the SS was less stable in the acidic medium. Both alum and SS were used, differently, for dye precipitation. The use of alum alone showed no precipitating effect on the AB dye molecules, whereas SS alone was able to reduce the dye concentration considerably. When the SS was used as a coagulant aid in alum precipitation, the percentage of the AB dye molecule removed increased. The effects of some process variables (coagulant/coagulant aid dosage, pH and flocculation time) were optimized by the method of continuous variation. The results obtained showed that an appreciable amount of the AB dye molecules was abstracted across the pH range, but the highest value was achieved at the lowest pH values. Studies on the effect of time on the flocculation of the precipitated AB molecule showed that the problem of redispersion and restabilization encountered in alum precipitation could be overcome using an alum–SS combination. The settling characteristics of the sludge obtained from the use of SS alone and an alum–SS combination were studied by measuring the sludge volume index (SVI, mg/g) over time. The value of the SVI showed that the sludge produced from the alum–SS combination had better settling characteristics than the sludge from the use of SS alone. Subsequent to the results obtained from the present studies, the use of the SS as a coagulant aid in the alum precipitation of the anionic dye as a unit process tertiary method of treatment in a suspended‐growth wastewater treatment system was proposed.

Equilibrium isotherm analysis of the sorption of congo red by palm kernel coat

The ability of Palm Kernel Coat (PKC), a waste agricultural product, in the abstraction of Congo Red (CR), an anionic dye, from aqueous solution was studied. The effects of sorbent dose and temperature were studied using batch sorption system. Isotherm experiments were conducted and the data obtained were fitted with different equilibrium isotherm equations namely, Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Harkins-Jura and Halsey isotherm equations. The Langmuir isotherm equation gave the best description of the sorption process and the maximum saturated monolayer sorption capacity of the PKC for CR was 79.37 mg g−1. Harkins-Jura isotherm equation gave the poorest description of the sorption process. The linear form of the Langmuir equation was used to analyze the data obtained when the sorbent dosage was optimized by method of continuous variation. The results obtained showed that the equilibrium monolayer sorption capacity, qm, of the PKC for CR decreased (79.37–17.07 mg g−1) with an increase in sorbent dosage. The relationship between the dimensionless parameter, KR, and initial concentration, Co, showed that the sorption of CR was favored at higher initial dye concentration and PKC dosages than the lower ones. The thermodynamic parameters, such as change in the free energy, the enthalpy and the entropy, were also evaluated. The thermodynamic analysis showed that the sorption is spontaneous and exothermic.

A critical review of the applicability of Avrami fractional kinetic equation in adsorption-based water treatment studies

AbstractThe need to stem the trend in the misuse and misinterpretation of the Avrami fractional kinetic equation in adsorption-based water treatment studies necessitated the present study. Taken into account, the theoretical basis and assumptions on which the derivation of the Avrami fractional kinetic equation is based, and the contexts in which it is being used in adsorption-based water research, the Avrami kinetic equation is being misused and misinterpreted. Most often, the mathematical model of the Avrami fractionary kinetic equation has no correlation with the proposed mechanism of sorption in the sorbent–sorbate system under investigation and the denotations given to the Avrami kinetic parameters obtained are flawed. In order to correct this problem, an expose on the original Avrami kinetic equation and cases of misuse and misinterpretation of this kinetic equation are presented. The proposed mechanisms of interactions, in each of the cases reviewed, when correlated with the assumptions and theoret...

Progress and Prospects of Polysaccharide Composites as Adsorbents for Water and Wastewater Treatment

In the last two decades, adsorbents have been developed from a variety of sources. Several of these adsorbents, though very efficient, are either still in their developmental stages in the laboratory or are not viable candidates for a large-scale treatment of water. Some of the adsorbents in the latter category are usually expensive to develop or suffer from certain drawbacks that ultimately influence negatively, their use in the large scale treatment of water. The development of polysaccharide-based adsorbents is considered a sustainable and green alternative that has future potentials to be used not only in the development of adsorbents but also membranes that are efficient in the treatment of water. This chapter reviews the progress made so far in the development of various polysaccharide-based adsorbents, their application in the removal of pollutants from water and a comparison of these adsorbents with conventional adsorbents. A look into some of the future issues surrounding the use of these polysaccharide-based adsorbents for water treatment and some of the challenges that may arise from their use as presented in this Chapter, could form the basis for future studies in the use of polysaccharide-based materials for water treatment.

Appropriate technology for domestic wastewater management in under-resourced regions of the world

Centralized wastewater management system is the modern day waste management practice, but the high cost and stringent requirements for the construction and operation have made it less attractive in the under-resourced regions of the world. Considering these challenges, the use of decentralized wastewater management system, on-site treatment system, as an appropriate technology for domestic wastewater treatment is hereby advocated. Adopting this technology helps save money, protects home owners’ investment, promotes better watershed management, offers an appropriate solution for low-density communities, provides suitable alternatives for varying site conditions and furnishes effective solutions for ecologically sensitive areas. In the light of this, an overview of the on-site treatment scheme, at the laboratory scale, pilot study stage, and field trials was conducted to highlight the operational principles’ strength and shortcomings of the scheme. The operational requirements for the establishing and operation of the scheme and best management practice to enhance the performance and sustenance were proffered.

Mechanistic Insight into the Coagulation Efficiency of Polysaccharide-based Coagulants

In order to optimise the coagulation efficiencies of polysaccharide-based coagulants (PBC), it is expedient that the underlying coagulation mechanism of this green resource should be elucidated to enable proper understanding of the process. Consequently, the present chapter provides an overview of the active coagulating species in PBCs that have been investigated in water and wastewater treatment operations. Based on the identities of the different active coagulating species in PBC, an insight into the underlying coagulation mechanisms of these varieties of coagulants are provided in this chapter.

THERMAL AGING PROPERTIES AND MOLECULAR TRANSPORT OF SOLVENTS THROUGH VULCANIZATES PREPARED FROM THIOGLYCOLLIC ACID MODIFIED EPOXIDIZED LOW MOLECULAR WEIGHT NATURAL RUBBER BLENDS FILLED WITH ADMIXTURES OF CARBON BLACK AND CARBONIZED RUBBER SEED SHELL

Physico-mechanical, aging, swelling, solubility, and permeability properties of blends of natural rubber (NR) and thioglycollic acid modified epoxidized low molecular weight natural rubber (TGA-ELMWNR) filled with admixtures of carbon black (CB) and carbonized rubber seed shell (CRSS) in ketones, alcohols, aldehydes, and petroleum fuels (petrol, kerosene, and diesel) were investigated as a function of different filler compositions. The physico-mechanical properties were found decreasing as the level of CRSS increases, but were within the accepted level for natural rubber compounds, showing that CRSS can find uses as fillers in materials of low tensile strength. The aging results of all the mixes were nearly of the same magnitude. The swelling and solubility results showed that ketones swell the vulcanizates more and faster than alcohols and aldehydes. The sorption, diffusion, and permeability of the blends as determined from the gravimetric method confirm the better resistance of blends with higher ratio of carbon black. Petrol was found diffusing through the vulcanizates faster than kerosene and faster than diesel. Above all, replacement of carbon black with 15% carbonized rubber seed shell has not shown any serious deleterious effects on the vulcanizates.