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The phenomenon of adsorption is widely exploited across a range of industries to remove contaminants from gases and liquids. Much recent research has focused on identifying low-cost adsorbents which have the potential to be used as alternatives to expensive industry standards like activated carbons. Evaluating these emerging adsorbents entails a considerable amount of labor intensive and costly testing and analysis. This study proposes a simple, low-cost method to rapidly assess the potential of novel media for potential use in large-scale adsorption filters. The filter media investigated in this study were low-cost adsorbents which have been found to be capable of removing dissolved phosphorus from solution, namely: i) aluminum drinking water treatment residual, and ii) crushed concrete. Data collected from multiple small-scale column tests was used to construct a model capable of describing and predicting the progression of adsorbent saturation and the associated effluent concentration breakthrough curves. This model was used to predict the performance of long-term, large-scale filter columns packed with the same media. The approach proved highly successful, and just 24–36 h of experimental data from the small-scale column experiments were found to provide sufficient information to predict the performance of the large-scale filters for up to three months. [ABSTRACT FROM AUTHOR]

This study reports the kinetics and isotherms of the adsorption of five herbicides, MCPA, mecoprop-P, 2,4-D, fluroxypyr and triclopyr, from aqueous solutions onto a range of raw and pyrolysed waste materials originating from an industrial setting. The raw waste materials investigated demonstrated little capability for any herbicide adsorption. Granulated activated carbon (GAC) was capable of the best removal of the herbicides, with >95% removal observed. A first order kinetic model fitted the data best for GAC adsorption of 2,4-D, while a pseudo-first order model fitted the data best for GAC adsorption of fluroxypyr and triclopyr, indicating that adsorption was via physisorption. A pseudo-second order kinetic model fitted the GAC adsorption of MCPA and mecoprop-P, which is indicative of chemisorption. The adsorption of the herbicides in all cases was best described by the Freundlich model, indicating that adsorption occurred onto heterogeneous surfaces. [Display omitted] • Adsorption of herbicides by waste materials and activated carbon investigated. • Activated carbon displayed best adsorption of herbicides. • Adsorption occurred via physisorption or chemisorption. • Adsorption of all herbicides best described by Freundlich model. [ABSTRACT FROM AUTHOR]

This study investigated a novel method of predicting the long-term phosphorus removal performance of large-scale adsorption filters, using data derived from short-term, small-scale column experiments. The filter media investigated were low-cost adsorbents such as aluminum sulfate drinking water treatment residual, ferric sulfate drinking water treatment residual, and fine and coarse crushed concretes. Small-bore adsorption columns were loaded with synthetic wastewater, and treated column effluent volume was plotted against the mass of phosphorus adsorbed per unit mass of filter media. It was observed that the curve described by the data strongly resembled that of a standard adsorption isotherm created from batch adsorption data. Consequently, it was hypothesized that an equation following the form of the Freundlich isotherm would describe the relationship between filter loading and media saturation. Moreover, the relationship between filter loading and effluent concentration could also be derived from this equation. The proposed model was demonstrated to accurately predict the performance of large-scale adsorption filters over a period of up to three months with a very high degree of accuracy. Furthermore, the coefficients necessary to produce said model could be determined from just 24 h of small-scale experimental data. [ABSTRACT FROM AUTHOR]

Forestry harvesting on peats is known to result in significant losses of soil phosphorus (P) to adjacent waters, and the issue is becoming an increasingly serious concern as peatland forest stocks mature and reach harvestable age. One potential solution could be the use of low-cost P recovery techniques based on the chemical precipitation and/or adsorption of the dissolved fraction of soil P, which would otherwise be lost. Such recovery techniques have shown promise in similar applications on mineral soils. However, the interaction of peat with P adsorbing materials can significantly alter their adsorptive characteristics, and it is consequentially not known what materials might be suitable for this application. This study compared the performance of six potential soil amendments (aluminum water treatment residual (Al-WTR), crushed concrete, gypsum, magnesium hydroxide, magnesium oxide, and steel wool) in removing P from aqueous solution in the presence of a typical forest peat soil. Comparison of adsorption isotherms plotted from these batch adsorption studies showed that the observed P adsorption maxima of Al-WTR and steel wool were increased by the presence of peat, from 10.6 mg g −1 and 20.4 mg g −1 , to 11.8 mg g −1 and 52.5 mg g −1 , respectively. In contrast, the observed P adsorption maxima of crushed concrete, gypsum, and magnesium oxide were reduced in the presence of peat, by 44%, 87%, and 37%, respectively. The maximum P adsorption achieved by magnesium hydroxide was increased from 29.8 mg g −1 to 59 mg g −1 at an amendment to peat–solid ratio of 1:4, but decreased from 73.9 mg g −1 to 23.6 mg g −1 at an amendment to peat–solid ratio of 1:10. It was concluded that Al-WTR, in particular, shows considerable promise for use as a soil amendment for P immobilization in a peat environment. [ABSTRACT FROM AUTHOR]

The use of filter media to adsorb phosphorus (P) from nutrient-rich waters is an effective, simple and low-cost method to recover and reuse P as an inorganic fertiliser replacement. Although it is assumed that the saturated filter media can be applied to cropland as a safe fertiliser replacement, there is presently a lack of information on the fertiliser replacement value (FRV) of such products and their negative effects on plants and soil. Therefore, the aims of this paper were to evaluate the (1) P removal capacity and plant response to soil application of waste media from three sectors (industry, agriculture, and construction and demolition), and natural and synthetic materials (2) potentially confounding risks arising from the reuse of media as a fertiliser replacement, and (3) factors affecting their fertilising efficiency once applied to soil. The predominant factors affecting the FRV of P-saturated media were their adsorption capacity and chemical composition, soil pH, and composition of water used for saturation. Some measures to overcome the negative impacts of the land application of P-saturated media include selecting the most appropriate soil-filter material combinations, the use of P solubilising microorganisms, and mixing with manure before land application. Despite confounding factors and a lack of information on the performance of some media under comparable study conditions, this study found that there is a significant potential for P-saturated filter media to partially replace the use of P mineral fertilisers and aid in the attainment of a "circular economy" in agriculture. Image 1 • Fertiliser success lies in the correct combination of filter medium, soil and water. • C&D, agriculture, industry, and natural/synthetic waste are potential fertilisers. • Adsorption capacity, composition, soil pH affect the fertiliser replacement value. • Significant potential for P-loaded filter media to replace P mineral fertilisers. [ABSTRACT FROM AUTHOR]