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Biochars showed a potential as adsorbents for organic contaminants, however, have not been tested for carbofuran, which has been detected frequently in water. This study provides evidences for the use of infused tea residue derived biochar for carbofuran removal. Biochars were produced at 300, 500 and 700 °C by slow pyrolysis and were characterized by proximate and ultimate analysis, FT-IR, SEM, BET and pore size distribution. Pyrolysis temperature showed a pronounced effect on biochar properties. The maximum carbofuran removal was achieved at pH 5. Freundlich and Temkin models best fit the equilibrium data. Biochars produced at 700 °C showed the highest sorption intensity. The adsorption process was likely to be a favorable chemisorption process with electrostatic interactions between carbofuran molecules and biochar surface. Acid-base interactions, electrophilic addition reactions and amide bond formations are the possible mechanisms of carbofuran adsorption. Overall, biochars prepared from tea waste can be utilized as effective adsorbents for removal of aqueous carbofuran.

This study reports the thermodynamic application and non-linear kinetic models in order to postulate the mechanisms and compare the carbofuran adsorption behavior onto rice husk and tea waste derived biochars. Locally available rice husk and infused tea waste biochars were produced at 700 °C. Biochars were characterized by using proximate, ultimate and surface characterization methods. Batch experiments were conducted at 25, 35, and 45 °C for a series of carbofuran solutions ranging from 5 to 100 mg L−1 with a biochar dose of 1 g L−1 at pH 5.0 with acetate buffer. Molar O/C ratios indicated that rice husk biochar (RHBC700) is more hydrophilic than tea waste biochar (TWBC700). Negative ΔG (Gibbs free energy change) values indicated the feasibility of carbofuran adsorption on biochar. Increasing ΔG values with the rise in temperature indicated high favorability at higher temperatures for both RHBC and TWBC. Enthalpy values suggested the involvement of physisorption type interactions. Kinetic data modeling exhibited contribution of both physisorption, via pore diffusion, π*−π electron donor–acceptor interaction, H-bonding, and van der Waals dispersion forces and chemisorption via chemical bonding with phenolic, and amine groups. Equilibrium adsorption capacities of RHBC and TWBC determined by pseudo second order kinetic model were 25.2 and 10.2 mg g−1, respectively.

Pyrolysis is the foremost thermal conversion process that can be successfully used to transform biomaterials into a value-added product. The estimated biodegradable portion is prominent and denotes as 60% from total waste generation in Asian developing countries. There have been several studies on exploring the pyrolysis of complex organic fraction of municipal solid waste (MSW) streams as a sustainable MSW management technique. The objective of this research was to evaluate physicochemical characteristics of MSW biochar (MSW-BC) produced from organic MSW to observe its potential for landfill contaminant removal with case studies from Sri Lanka. Biochar was pyrolyzed from the MSW in an onsite pyrolyzer. For physicochemical properties of biochar, pH, point of zero charge, electrical conductivity, proximate analysis, ultimate analysis, heavy metal composition, bioavailable heavy metal composition and BET surface area were acquired. In addition, surface functional groups and structural identification were determined by FTIR analysis and scanning electron microscopy (SEM) analysis, respectively. Adsorption capacities for the pollutants (benzene and toluene) were examined by batch sorption experiments. Furthermore, sorption isotherms were fitted using non-linear models for better understanding of the sorption capacities of the materials. Ultimate analysis data suggested high-temperature pyrolysis of MSW. Further, low values for both H/C and polarity index depict the strongly carbonized and highly aromatic structure in BC. Additionally, FTIR suggested a loss of labile, aliphatic compounds and functional groups during pyrolysis and the formation of more recalcitrant, aromatic constituents, whereas BET and SEM data revealed a well-developed porous structure and surface properties, which indicates MSW-BC to be a potential sorbent. Further, the reported total and bioavailable heavy metal content was low in MSW-BC; hence, it can be easily mixed with compost and used as a fertilizer. At the same time, MSW-BC will potentially be used to remediate heavy metals in the landfill leachate. Therefore, MSW-BC shows high potential to be used as a material to remediate contaminants simultaneously that minimizes MSW volume. Thus, conversion of MSW to BC and chemical and thermal modification of MSW-BC would allow effective engineering to optimize their properties as a potential material in landfill covers and permeable reactive barriers and integrate in leachate treatment techniques.

The potential of biochar, produced from fibrous organic fractions of municipal solid waste (MSW), for remediation of benzene, one of the frequently found toxic volatile organic compounds in landfill leachate, was investigated in this study based on various environmental conditions such as varying pH, benzene concentration, temperature and time. At the same time, landfill leachate quality parameters were assessed at two different dump sites in Sri Lanka: Gohagoda and Kurunegala. MSW biochar (MSW-BC) was produced by slow temperature pyrolysis at 450 °C, and the physiochemical characteristics of the MSW-BC were characterized. All the leachate samples from the MSW dump sites exceeded the World Health Organization permissible level for benzene (5 µg/L) in water. Removal of benzene was increased with increasing pH, with the highest removal observed at ~pH 9. The maximum adsorption capacity of 576 µg/g was reported at room temperature (~25 °C). Both Freundlich and Langmuir models fitted best with the equilibrium isotherm data, suggesting the involvement of both physisorption and chemisorption mechanisms. Thermodynamic data indicated the feasibility of benzene adsorption and its high favorability at higher temperatures. The values of $$\Delta G$$ suggested physical interactions between sorbate and sorbent, whereas kinetic data implied a significant contribution of chemisorption. Results obtained from FTIR provided clear evidence of the involvement of functional groups in biochar for benzene adsorption. This study suggests that MSW biochar could be a possible remedy for benzene removal from landfill leachate and at the same time MSW can be a potential source to produce biochar which acts as a prospective material to remediate its pollutants while reducing the volume of waste.

Extract and analysis of the Dissolved Organic Carbon (DOC) fractions were analyzed from the leachate of an uncontrolled dumpsite at Gohagoda, Sri Lanka. DOC fractions, humic acid (HA), fulvic acid (FA) and the hydrophilic (Hyd) fractions were isolated and purified with the resin techniques. Spectroscopic techniques and elemental analysis were performed to characterize DOCs. Maximum TOC and DOC values recorded were 56,955 and 28,493 mg/L, respectively. Based on the total amount of DOC fractionation, Hyd dominated accounting for ∼60%, and HA and FA constituted ∼22% and ∼17%, respectively, exhibiting the mature phase of the dumpsite. The elemental analysis of DOCs revealed carbon variation following HAFAHyd, while hydrogen and nitrogen were similar in each fraction. The N/C ratio for HA was recorded as 0.18, following a similar trend in old dumpsite leachate elsewhere. The O/C ratios for HA and FA were recorded higher as much as 1.0 and 9.3, respectively, indicating high degree of carbon mineralization in the leachates. High content of carboxylic, phenolic and lactone groups in all DOCs was observed disclosing their potential for toxic substances transportation. The results strongly suggest the risk associated with DOCs in dumpsite leachate to the aquatic and terrestrial environment.

Background Iodine is an essential micronutrient used by the thyroid gland in the production of thyroid hormones. Both excessive and insufficient iodine intakes can cause thyroid diseases thus harmful to the human body. Inadequate iodine intake by human body causes Iodine Deficiency Disorders (IDD) and hypothyroidism. Excessive iodine intake causes Iodine Induced Hyperthyroidism (IIH). Universal Salt Iodization (USI) is the most effective way of preventing IDD. This study determined the concentrations of iodine species in commercial edible salt products, the stability of iodine at different conditions and iodine exposure at the consumer level. Methods The iodine contents of six commercial edible iodized salts were determined qualitatively and quantitatively for both iodide and iodate. Thereafter, the first three products of highest iodine contents, the stability of iodide at exposed to air and heat was measured after 24 hours. Risk assessment of exposure was done at four levels considering the WHO estimation. Results Results revealed that all of the salt products have excess iodine that is above the fortification level of 15–30 mg kg−1 level in Sri Lanka. Iodide stability was reduced at the average percentages of 13.1, 10.7 and 11.3. The iodate loss percentages were 0, 5.7 and 0 at open air. The iodide loss percentages at the temperature of 50 °C were 4.6, 7.8 and 8.6 while at 100 °C, loss percentages were 11.1, 11.4 and 15.9 for the same salt products. The iodine exposure at lower consumption during cooking ranged 244.4–432.2 μg/day while 325.9–576.3 μg/day for medium consumption, 407.4–720.4 μg/day for moderate high salt consumptions and 488.8–864.4 μg/day for high salt consumptions. As a total 95.8 % cases can cause IIH and only 4.1 % of them can provide optimal iodine nutrition in a population. Iodine exposure without cooking ranged 305.5–540.3 μg/day for low salt consumption, 407.4–720.4 μg/day for medium consumption and 509.2–900.5 μg/day for moderate high consumption and 611.1–1080.6 μg/day for high salt consumptions. Conclusions All of the incidents (100 %) of consumption without cooking at the household level can cause excessive iodine intake and IIH in a population.

Biochar has been considered as a potential sorbent for removal of frequently detected pesticides in water. In the present study, modified and non-modified rice husk biochars were used for aqueous carbofuran removal. Rice husk biochars were produced at 300, 500, and 700 °C in slow pyrolysis and further exposed to steam activation. Biochars were physicochemically characterized using proximate, ultimate, FTIR methods and used to examine equilibrium and dynamic adsorption of carbofuran. Increasing pyrolysis temperature led to a decrease of biochar yield and increase of porosity, surface area, and adsorption capacities which were further enhanced by steam activation. Carbofuran adsorption was pH-dependant, and the maximum (161 mg g−1) occurred in the vicinity of pH 5, on steam-activated biochar produced at 700 °C. Freundlich model best fitted the sorption equilibrium data. Both chemisorption and physisorption interactions on heterogeneous adsorbent surface may involve in carbofuran adsorption. Langmuir kinetics could be applied to describe carbofuran adsorption in a fixed bed. A higher carbofuran volume was treated in a column bed by a steam-activated biochar versus non-activated biochars. Overall, steam-activated rice husk biochar can be highlighted as a promising low-cost sustainable material for aqueous carbofuran removal.

We investigated the removal of aqueous glyphosate using woody (dendro) biochar obtained as a waste by product from bioenergy industry. Equilibrium isotherms and kinetics data were obtained by adsorption experiments. Glyphosate adsorption was strongly pH dependent occurring maximum in the pH range of 5-6. The protonated amino moiety of the glyphosate molecule at this pH may interact with π electron rich biochar surface via π-π electron donor-acceptor interactions. Isotherm data were best fitted to the Freundlich and Temkin models indicating multilayer sorption of glyphosate. The maximum adsorption capacity of dendro biochar for glyphosate was determined by the isotherm modeling to be as 44 mg/g. Adsorption seemed to be quite fast, reaching the equilibrium

Landfills are one of the most historical and ordinary methods of waste disposal and still remain in many parts of the world. Landfill leachate from open dumpsites has become a crucial environmental issue. Still, the predominant waste disposal method in many developing countries is open dumping, which leads to the generation of significant amounts of leachate mostly to nearby water bodies. Landfill leachate treatment is not an easy task, specifically because of its uniqueness depending on climate, culture, age of the dumpsite, and waste characteristics. Acetogenic leachate characteristics are extremely variable and difficult to predict. However, landfill leachate in the methanogenic phase possesses quite stable characteristics. Herein, we report qualitative and quantitative data on landfill leachate from different parts of the world and discuss the best management practices. In addition, we provide a case study on assessing the physiochemical characteristics of landfill leachate generated from a municipal solid waste dumpsite in Sri Lanka. Overall, landfill leachate poses a risk to the environment and effective leachate management is vital to avoid environmental deterioration.