Recent investigations have revealed the harmful health effects of elevated calcium levels in drinking water. Chemically activated biochar is the most popular option for low-cost cation adsorption. However, most of these chemicals are hardly available for rural communities, corrosive, and difficult to handle by unskilled personnel. This study aimed to determine the ability of natural coconut vinegar, a common mild acid, to activate Trema orientalis wood biochar pyrolyzed at 300˚C (BC) as a facile, safe, and low-cost approach for aqueous calcium ion (Ca2+) removal. Column tests showed a two-fold increase of Ca2+ adsorption capacity and a ten-fold increase of Ca2+ retaining capacity of BC after activation with vinegar. The isotherm results were well correlated with the Langmuir model. The maximum Langmuir adsorption of the activated biochar (BC-A) was 9.96 mg/g. Ca2+ amount was determined using flame photometry. EDX analysis showed that the O/C ratio of BC increased from 0.07 to 0.13 after activation. FTIR and wettability studies showed increased oxygenated functional groups on the BC-A surface. The authors suggest a possible acid-catalyzed hydration of the C-O-C bridges of the biochar, introducing new hydroxyl/carbonyl/ester/carboxylic/lactone groups to the biochar surface due to the vinegar activation, enhancing Ca2+ adsorption through chemisorption.

Microplastic pollution (MP) in marine environments around the globe is severe and insufficient precautions have yet to be taken for its prevention. The focus of this study was on quantifying MPs from beach sediment and seawater samples and identifying their distributions and types along the western coast of Sri Lanka from the Kelani River estuary to the Mahaoya estuary. Nine sites along this 42 km stretch were selected, and random sampling was employed to collect a minimum of eight sediment samples from each site between October and December 2021. Water samples were also collected, parallel to the sediments, from the ocean surface. FTIR analysis revealed that most of the MPs found were polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and phenol formaldehyde resin. The mean abundance of MPs varied from 2.0 ± 0.6 items/L to 161.0 ± 15.7 items/L in water samples and from 3.0 ± 0.3 items/m² to 656.0 ± 34.5 items/m² in sediment samples. The MPs found were identified in different shapes as fragments (80.2%), pellets (14.9%), fibers (2.7%), and foams (2.5%). Analysis revealed that the beach sediments were contaminated with PS, phenol formaldehyde resin, PET, PP, and PE, while the surface seawater was dominated by phenol formaldehyde resin, PS, PP, and PE.

Aluminium is the most abundant metal in the earth’s crust. In soil, aluminum is mainly found in the mineral form as aluminosilicates and aluminum oxides and this aluminium is in stable inactive form. In addition, Al can be found as precipitates or in very minute quantities appear in soluble forms such as conjugated organic and inorganic, and molecular ions. Aluminium mobility and as a consequence aluminium toxicity, is mainly restricted to acid environments. Depending on the soil pH these mobile forms are capable of influencing biological systems. Aluminium has low mobility under most environmental conditions. However, below a pH of 4.0 its solubility increases and aluminium is released from silicate rocks under such acidic conditions. The levels of dissolved aluminium in natural groundwater samples are generally low, probably due to its low solubility at neutral pH values. Release of acids by anthropogenic activities influence the soil acidity levels. Therefore, elevated levels of aluminium have been found in acidified soil solutions and surface waters causing harmful effects to living organisms. The present study was aimed at proving the above theoretical hypothesis and existence of a possible relationship between soil salinity and soil acidity on the concentration of mobile aluminium ions in samples obtained during the location surveys. Samples were collected from selected locations in Ratnapura, Rathupaswala, Marawila, Mabima and Muthurajawela to get different soil types and the survey results were used to test the hypothetical relationship between the presence of the stated factors, and the existence of a high concentration of mobile aluminium in the soil water samples. The analysis covered basic parameters such as soil pH, soil cation exchange capacity (CEC), soil organic matter, soil electrical conductivity and the influence of the concentration of mobile aluminium at different pH and Na⁺ concentration levels. The total aluminium concentration in the soil was assayed by digesting samples with strong acid. Concentration of mobile aluminium in soil samples were analyzed using the flame atomic absorption spectrophotometry. The results indicated that there is no clear relationship between mobile aluminium and total aluminium in the soil. It was also found that the concentration of mobile aluminium released increased with decrease in soil pH and that the increase was marked when the pH of soil water was less than 4.0. Highest mobile aluminium release to the soil solution was found from Mabima sites [at pH 5.00 was 0.54 (±0.06) mg kg^-1 of dry soil, at pH 0.00 was 90.12 (±7.01) mg kg^-1] and least in samples from Marawila sites [at pH 5.00 was 0.48 (±0.03) mg kg^-1, at pH 0.00 was 4.52 (±0.36) mg kg^-1]. This result confirmed that there is an effect of soil acidity on the concentration of mobile aluminium in the soil but with no direct correlation. Results also showed that the concentration of mobile aluminium released increased with increasing soil salinity and that the increase was rapid when the Na⁺ ion concentration was higher than 2.0 %. Highest mobile aluminium release to the soil solution was found from Muthurajawela sites [Na⁺ 1.0% = lower than detection limit, Na⁺ 5.0% = 9.87 (±0.67) mg kg^-1] and least found from Marawila sites [Na⁺1.0% = lower than detection limit, Na⁺ 5.0% = 2.24 (±0.23) mg kg^-1] confirming the effect of soil salinity on the concentration of mobile aluminium in the soil. The study also points towards the future opportunities for research to confirm these findings using wider samples and employing more vigorous research methodologies.

A positive correlation has been reported recently among the number of Chronic Kidney Disease of Unknown Etiology (CKDu) patients and the levels of groundwater hardness. Hence, the need for a low cost and a simple domestic process to reduce the hardness of potable water is identified to improve living standards of low-income communities in these disease affected areas. Biochar has emerged as a low cost adsorbent for water treatment, because of its abundance and cost-effectiveness. This study was aimed to evaluate the ability of natural coconut vinegar, in activating Leucaena leucocephala wood biochar to be used in calcium ion (Ca2+) removal from potable water. Column tests showed a 1.7 fold increase of Ca2+ adsorption capacity and a 7 fold increase of Ca2+ retaining capacity upon the vinegar treatment. Batch studies matched with both Langmuir (R2 = 0.9761) and Freundlich (R2 = 0.9785) isotherm models. Ca2+ amount in solutions were measured using flame photometry. Ca2+ adsorption capacities of raw biochar and activated biochar determined by column tests ranged from 3.10-3.82 mg/g and 5.27-6.68 mg/g respectively while Ca2+ retaining capacities ranged from 0.16-0.22 mg/g and 1.28-1.4 mg/g respectively. Fourier transform infrared spectra, suggests hydration of the C-O-C bridges of the biochar surface introducing new -O-H groups and possible introduction of carbonyl/ ester/carboxylic functional groups to the biochar surface upon vinegar treatment. According to scanning electron microscopy porosity of the biochar remained stable after the vinegar treatment.

Biochar is widely utilized in low-cost water treatment. However, chemicals used in most of the recorded activation techniques are corrosive, may cause secondary pollution, and not accessible by rural communities, reducing their value of being cost-effective. In this study, Trema orientalis wood biochar (WB) was successfully activated with natural coconut vinegar employing a facile technique to produce a green adsorbent for efficient aqueous methylene blue (MB) removal. Batch studies showed a three-fold higher MB adsorption capacity of coconut vinegar treated wood biochar (CVWB) compared to WB. Percentage removal ranged between 98-79% at lower dye concentrations (50-100 mg/L) and 79-48% at higher dye concentrations (100-300 mg/L). Isotherm data best fitted to the Freundlich model. Kinetic data fitted to both pseudo second order and intraparticle diffusion models, suggesting that the adsorption was governed by a pore filling mechanism with predominant electrostatic attractions, and the reaction rate was diffusion controlled. FTIR, XPS, and water contact angle measurements confirmed increased surface oxygenated groups of CVWB. XPS showed a three-fold increase in O/C atomic ratio. BET and AFM studies gave evidence to the increased porosity. Therefore, the enhanced MB adsorption capacity of CVWB was attributed to both the increased surface oxygenated functional groups and porosity.

Microplastic pollution (MP) in marine environments around the globe is severe and enough precautions have not been taken so far for its prevention. The focus of this study is to quantify MPs from beach sediment and seawater samples and to identify their distribution and types along the western coast of Sri Lanka from the Kelani River estuary to the Mahaoya estuary. Nine sites along this 42 km stretch were selected and random sampling was employed to collect a minimum of 8 sediment samples from each site between October and December 2021. Water samples were also collected, parallel to the sediments, from the ocean surface. FTIR analysis revealed that most of the MPs found were polyethylene(PE), polypropylene(PP), polystyrene(PS), polyethylene terephthalate(PET), and phenol formaldehyde resin. The mean abundance of MPs varied from 2.0 ± 0.6 items/L to 161.0 ± 15.7 items/L in water samples and, from 3.0 ± 0.3 items/m2 to 656.0 ± 34.5 items/m2 in sediment samples. The MPs found were identified in different shapes as fragments (80.2%), pellets (14.9%), fibers (2.7%) and foams (2.5%). Analysis revealed that the beach sediments were contaminated with PS, phenol formaldehyde resin, PET, PP and PE, while surface seawater is dominated by phenol formaldehyde resin, PS, PP and PE.